Murata Electronics North America DNT500P DNT500 900 MHz Transceiver Module User Manual part 1

Murata Electronics North America DNT500 900 MHz Transceiver Module part 1

part 1 user manual

DNT500 Series 900 MHz Spread Spectrum Wireless Industrial Transceivers Integration Guide 3079 Premiere Pkwy Ste 140 Norcross, Georgia 30097 www.rfm.com +1 (678) 684-2000
Important Regulatory Information RFM Product FCC ID: HSW-DNT500P IC 4492A-DNT500P The DNT500 has been designed to operate with the RWA092R 2 dBi reverse-pin (polarity) SMA sleeved dipole antenna (U.FL female to reverse-pin SMA female adaptor or equivalent required). See section 3.10 of this manual for regulatory notices and labeling requirements. Changes or modifica-tions not expressly approved by RFM may void the user’s authority to operate the module. Note: This unit has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communica-tions. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at their expense.
TABLE OF CONTENTS 1. INTRODUCTION................................................................................................................1 1.1 Why Spread Spectrum?................................................................................................... 1 1.2 Frequency Hopping versus Direct Sequence .................................................................. 2 2. DNT500 RADIO OPERATION ..........................................................................................4 2.1 Network Synchronization and Registration .................................................................... 4 2.2 Transparent and Protocol Serial Port Modes................................................................... 4 2.3 RF Data Communications............................................................................................... 5 2.4 RF Transmission Error Control....................................................................................... 5 2.5 Network Configurations.................................................................................................. 6 2.5.1 Point-to-Point Network Operation ..........................................................................6 2.5.2 Point-to-Multipoint Network Operation..................................................................7 2.6 Full-Duplex Serial Data Communications...................................................................... 7 2.7 Channel Access ............................................................................................................... 7 2.7.1 CSMA Modes..........................................................................................................8 2.7.2 TDMA Modes .........................................................................................................9 2.7.3 Network Configuration Planning ..........................................................................10 2.7.4 Serial Port Operation.............................................................................................12 2.7.5 Sleep Mode............................................................................................................13 3. DNT500 HARDWARE......................................................................................................14 3.1 Specifications ................................................................................................................ 15 3.2 Module Interface ........................................................................................................... 16 3.3 Input Voltages ............................................................................................................... 17 3.4 ESD and Transient Protection....................................................................................... 17 3.5 Interfacing to 5 V Logic Systems.................................................................................. 18 3.6 Power-On Reset Requirements ..................................................................................... 18 3.7 Analog RSSI Output...................................................................................................... 18 3.8 Mounting and Enclosures.............................................................................................. 18 3.9 Connecting Antennas .................................................................................................... 19 3.10 Labeling and Notices..................................................................................................... 19 4. PROTOCOL MESSAGES.................................................................................................20 4.1 Protocol Message Formats ............................................................................................ 20 4.1.1 Serial message types..............................................................................................20 4.1.2 Escape sequence....................................................................................................22 4.1.3 CFG select pin.......................................................................................................23 4.1.4 Flow control .......................................................................................................... 23 4.1.5 Protocol mode data message example...................................................................23 4.2 Configuration Registers................................................................................................. 23 4.2.1 Bank 0 - Transceiver Setup...................................................................................24 4.2.2 Bank 1 - System Settings ......................................................................................26 4.2.3 Bank 2 - Status Registers (read only)...................................................................28 4.2.4 Bank 3 - Serial......................................................................................................30
4.2.5 Bank 4 - Host Protocol Settings...........................................................................31 4.2.6 Bank 5 - I/O Peripheral Registers ........................................................................33 4.2.7 Bank 6 - I/O setup ................................................................................................33 4.2.8 Bank FF - Special function...................................................................................36 4.2.9 Protocol Mode Configuration/Sensor Message Examples....................................36 4.2.10 Protocol Mode Event Message Examples.............................................................37 5. DNT500 DEVELOPER’S KIT ..........................................................................................38 5.1 DNT500DK Kit Contents.............................................................................................. 38 5.2 Additional Items Needed............................................................................................... 38 5.3 Developer’s Kit Default Operating Configuration........................................................ 39 5.4 Development Kit Hardware Assembly ......................................................................... 39 5.5 DNT500 Wizard Utility Program.................................................................................. 41 5.6 DNT500 Interface Board Features................................................................................ 47 6. Demonstration Procedure...................................................................................................50 7. Troubleshooting..................................................................................................................51 8. APPENDICES....................................................................................................................52 8.1 Ordering Information .................................................................................................... 52 8.2 Technical Support ......................................................................................................... 52 8.3 DNT500 Mechanical Specifications ............................................................................. 53 9. Warranty.............................................................................................................................55
DNT500  2008 by RF Monolithics, Inc. 1 M-0500-0000 Rev D 1. INTRODUCTION The DNT500 series transceivers provide highly reliable wireless connectivity for either point-to-point or point-to-multipoint applications. Frequency hopping spread spectrum (FHSS) technology ensures maximum resistance to multipath fading and robustness in the presence of interfering signals, while operation in the 900 MHz ISM band allows license-free use in the US, Canada, Australia and New Zealand. The DNT500 supports all standard serial data rates for host communications from 1.2 to 460.8 kb/s. On-board data buffering and an error-correcting air protocol provide smooth data flow and sim-plify the task of integration with existing applications. Key DNT500 features include: - Multipath fading impervious fre-quency hopping technology with up to 50 frequency channels (902 to 928 MHz). - Supports point-to-point or multi-point applications. - Meets FCC rules 15.247 for li-cense-free operation. - 20 mile plus range with omni-directional antennas. - Transparent ARQ protocol with buffering ensures data integrity. - Selectable 0, 10, 19, 24, 27 or 28 dBm transmit power with a firmware interlock of 19 dBm maxi-mum for 500 kb/s operation. - Built-in data scrambling reduces possibility of eavesdropping. - Nonvolatile memory stores configu-ration when powered off. - Dynamic TDMA slot assignment that maximizes throughput. - Simple serial interface handles both data and control at up to 460.8 kb/s. 1.1 Why Spread Spectrum? A radio transmission channel can be very hostile, corrupted by noise, path loss and interfering transmissions from other radios. Even in an interference-free environment, radio performance faces serious degradation through a phenomenon known as multi-path fading. Multipath fading results when two or more reflected rays of the transmit-ted signal arrive at the receiving antenna with opposing phases, thereby partially or completely canceling the signal. This is a problem particularly prevalent in indoor in-stallations. In the frequency domain, a multipath fade can be described as a fre-quency-selective notch that shifts in location and intensity over time as reflections change due to motion of the radio or objects within its range. At any given time, mul-tipath fades will typically occupy 1% - 2% of the band. This means that from a prob-abilistic viewpoint, a conventional radio system faces a 1% - 2% chance of signal im-pairment at any given time due to multipath. Spread spectrum reduces the vulnerability of a radio system to interference from both jammers and multipath fading by distributing the transmitted signal over a larger re-gion of the frequency band than would otherwise be necessary to send the informa-tion. This allows the signal to be reconstructed even though part of it may be lost or corrupted in transit.
DNT500  2008 by RF Monolithics, Inc. 2 M-0500-0000 Rev D Figure1 Narrowband vs. spread spectrum in the presence of interference 1.2 Frequency Hopping versus Direct Sequence The two primary approaches to spread spectrum are direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS), either of which can gener-ally be adapted to a given application. Direct sequence spread spectrum is produced by multiplying the transmitted data stream by a much faster, noise-like repeating pat-tern. The ratio by which this modulating pattern exceeds the bit rate of the base-band data is called the processing gain, and is equal to the amount of rejection the system affords against narrowband interference from multipath and jammers. Transmitting the data signal as usual, but varying the carrier frequency rapidly according to a pseudo-random pattern over a broad range of channels produces a frequency hopping spectrum system. Figure 2 Forms of spread spectrum
DNT500  2008 by RF Monolithics, Inc. 3 M-0500-0000 Rev D One disadvantage of direct sequence systems is that due to spectrum constraints and the design difficulties of broadband receivers, they generally employ only a minimal amount of spreading (typically no more than the minimum required by the regulating agencies). For this reason, the ability of DSSS systems to overcome fading and in-band jammers is relatively weak. By contrast, FHSS systems are capable of probing the entire band if necessary to find a channel free of interference. Essentially, this means that a FHSS system will degrade gracefully as the channel gets noisier while a DSSS system may exhibit uneven coverage or work well until a certain point and then give out completely. Because it offers greater immunity to interfering signals, FHSS is often the preferred choice for co-located systems. Since direct sequence signals are very wide, they tend to offer few non-overlapping channels, whereas multiple hoppers may interleave with less interference. Frequency hopping does carry some disadvantage in that as the transmitter cycles through the hopping pattern it is nearly certain to visit a few blocked channels where no data can be sent. If these channels are the same from trip to trip, they can be memorized and avoided. Unfortunately, this is generally not the case, as it may take several seconds to completely cover the hop sequence during which time the multipath delay profile may have changed substantially. To ensure seamless operation throughout these outages, a hopping radio must be capable of buffering its data until a clear channel can be found. A second consideration of fre-quency hopping systems is that they require an initial acquisition period during which the receiver must lock on to the moving carrier of the transmitter before any data can be sent, which typically takes several seconds. In summary, frequency hop-ping systems generally feature greater coverage and channel utilization than compa-rable direct sequence systems. Of course, other implementation factors such as size, cost, power consumption and ease of implementation must also be considered before a final radio design choice can be made. DNT500 series modules achieve regulatory certification under FHSS rules at air data rates of 38.4, 115.2 and 200 kb/s. At 500 kb/s, the DNT500 series modules achieve regulatory certification under “digital modulation” or DTS rules. At 500 kb/s DNT500 series modules still employ frequency hopping to mitigate the effects of in-terference and multipath fading, but hop on fewer, more widely spaced frequencies than at lower data rates.
DNT500  2008 by RF Monolithics, Inc. 4 M-0500-0000 Rev D 2. DNT500 RADIO OPERATION 2.1 Network Synchronization and Registration As discussed above, frequency hopping radios such as the DNT500 periodically change the frequency at which they transmit. In order for the other radios in the network to re-ceive the transmission, they must be listening to the frequency over which the current transmission is being sent. To do this, all the radios in the network must be synchronized and must be set to the same hopping pattern. In point-to-point or point-to-multipoint networks, one radio module is designated as the base station. All other radios are designated remotes. One of the responsibilities of the base station is to transmit a synchronization signal to the remotes to allow them to syn-chronize with the base station. Since the remotes know the hopping pattern, once they are synchronized with the base station, they know which frequency to hop to and when. Every time the base station hops to a different frequency, it immediately transmits a syn-chronizing signal. When a remote is powered on, it rapidly scans the frequency band for the synchronizing signal. Since the base station is transmitting up to 50 frequencies and the remote is scan-ning up to 50 frequencies, it can take several seconds for a remote to synchronize with the base station. Once a remote has synchronized with the base station, it will request registration informa-tion to allow it to join the network. Registration can be handled automatically by the base station, or it can be controlled by allowing the base station host application to authenti-cate the remote for registration. When a remote is registered, it receives several network parameters from the base station, including HopDuration, Nwk_ID, FrequencyBand and Nwk_Key (see Section 5.2 for parameter details). Note that if a registration parameter is changed at the base station, it will update the parameter in the remotes over the air. Among other things, registration allows the tracking of remotes entering and leaving a network, up to a limit of 255 remotes. The base station builds a table of serial numbers of registered remotes using their three-byte serial numbers (MAC addresses). To detect if a remote has gone offline or out of range, the registration is “leased” must be “renewed” once every 250 hops. Any transmission from a remote running on a leased registration will renew its lease with the base station. 2.2 Transparent and Protocol Serial Port Modes DNT500 radios can work in two serial port data modes: transparent and packet protocol. Transparent formatting is simply the raw user data. Packet protocol formatting uses a framing character, length byte, addressing, command bytes, etc. Transparent mode opera-tion is especially useful in point-to-point systems that act as simple cable replacements. In point-to-multipoint systems where the base station needs to send data specifically to each remote, protocol formatting must be used. Protocol formatting is also required for configuration commands and responses, and sensor I/O commands and responses. Proto-col formatting details are covered in Section 5.
DNT500  2008 by RF Monolithics, Inc. 5 M-0500-0000 Rev D The DNT500 provides two ways to switch between transparent and protocol modes. If CFG input Pin 18 on the DNT500 is switched from logic high to low, protocol mode is invoked. Or if the ASCII escape sequence “DNT500” is sent (without quotation marks) to the primary serial input following at least a 20 ms pause in data flow, the DNT500 will switch to the protocol mode. When input Pin 18 is switched from logic low to high, or an ExitProtocolMode command is sent to the primary serial input, the DNT500 will switch to transparent operation. Note that if the escape sequence is used to switch to protocol mode, the sequence will be transmitted before protocol mode is invoked. When operating in transparent mode, two configuration parameters control when a DNT500 radio will send the data in its transmit buffer. The MinPacketLength parameter sets the minimum number of bytes that must be present in the transmit buffer to trigger a transmission. The TxTimeout parameter sets the maximum time data in the transmit buffer will be held before transmitting it, even if the number of data bytes is less than MinPacketLength. The default value for both the MinPacketLength and the TxTimeout parameters is zero, so that any bytes that arrive in the DNT500 transmit buffer will be sent on the next hop. As discussed in Section 2.7.3, it is useful to set these parameters to non-zero values in point-to-multipoint systems where some or all the remotes are in transparent mode. 2.3 RF Data Communications At the beginning of each hop, the base station transmits a synchronizing signal. After the synchronizing signal has been sent, the base will transmit any user data in its transmit buffer, unless in transparent mode the MinPacketLength and/or TxTimeout parameters have been set to non-zero. The maximum amount of user data that the base station can transmit per hop is limited by the BaseSlotSize parameter, which has a maximum value of 232 bytes. If there is no user data or reception acknowledgements (ACKs) to be sent on a hop, the base station will only transmit the synchronization signal. The operation for remotes is similar to the base station, but without the synchronizing signal. The RemoteSlotSize parameter sets the maximum number of user bytes a remote can transmit on one hop, up to a limit of 243 bytes per hop. The RemoteSlotSize must be coordinated with the HopDuration and BaseSlotSize parameters and the number of regis-tered remotes, as discussed in Section 2.5.3. The MinPacketLength and TxTimeout pa-rameters operate in a remote in the same manner as in the base station. 2.4 RF Transmission Error Control The DNT500 supports two error control modes: redundant transmissions and automatic transmission repeats (ARQ). In both modes, the radio will detect and discard any dupli-cates of messages it receives so that the host application will only receive one copy of a given packet. Packet IDs are included in each transmission to allow recipients to identify if the packet is new or has been received before. In the redundant transmission mode, packets are repeated a fixed number of times with-out any acknowledgement (ACK) from the recipient. This error control method is useful in latency-critical applications such as voice, video and real-time telemetry, where only a
DNT500  2008 by RF Monolithics, Inc. 6 M-0500-0000 Rev D few transmission repeats can be made before the current data is replaced with new data. It is wasteful of bandwidth to send ACKs in these types of applications. Redundant trans-missions are also used where messages are broadcast to multiple recipients and it is not practical to receive ACKs from each one. In ARQ mode, a packet is sent and an acknowledgement is expected on the next hop. If an acknowledgement is not received, the packet is transmitted again on the next available hop until either an ACK is received or the maximum number of attempts is exhausted. If the AttemptLimit parameter is set to its maximum value, a packet transmission will be re-tried without limit until the packet is acknowledged. This is useful in some point-to-point cable replacement applications where it is important that data truly be 100% error-free, even if the destination remote goes out of range temporarily. 2.5 Network Configurations The DNT500 supports two network configurations: point-to-point and point-to-multipoint. In a point-to-point network, one radio is set up as the base station and the other radio is set up as a remote. In a point-to-multipoint network, a star topology is used with the radio set up as a base station acting as the central communications point and all other radios in the network set up as remotes. In this configuration, all communications take place between the base station and any one of the remotes. Remotes cannot commu-nicate directly with each other. It should be noted that point-to-point operation is a subset of the point-to-multipoint operation, so there is no need to specify one or the other. 2.5.1 Point-to-Point Network Operation Most point-to-point networks act as serial cable replacements and both the base station and the remote use transparent mode. Unless the MinPacketLength and TxTimeout pa-rameters have been set to non-zero, the base station will send the data in its transmit buffer on each hop, up to the limit set by the BaseSlotSize parameter, less ACK bytes. If the base station is buffering more data than can be sent on one hop, the remaining data will be sent on subsequent hops. The base station adds the address of the remote, a packet sequence number and error checking bytes to the data when it is transmitted. These addi-tional bytes are not output at the remote in transparent mode. The sequence number is used in acknowledging successful transmissions and in retransmitting corrupted transmis-sions. A two-byte CRC and a one-byte checksum allows a received transmission to be checked for errors. When a transmission is received by the remote, it will be acknowl-edged if it checks error free. If no acknowledgment is received, the base station will re-transmit the same data on the next hop. In point-to-point operation, by default the remote will send the data in its transmit buffer on each hop, up to the limit set by its RemoteSlotSize parameter. If desired, the MinPack-etLength and TxTimeout parameters can be set to non-zero values, which configures the remote to wait until the specified amount of data is available or the specified delay had expired before transmitting. If the remote is buffering more data than can be sent on one hop, it will send the remaining data in subsequent hops. The remote adds its own address, a packet sequence number and error checking bytes to the data when it is transmitted. These additional bytes are not output at the base station if the base station is in transpar-ent mode. When a transmission is received by the base station, it will be acknowledged if
DNT500  2008 by RF Monolithics, Inc. 7 M-0500-0000 Rev D it checks error free. If no acknowledgment is received, the remote will retransmit the same data on the next hop. 2.5.2 Point-to-Multipoint Network Operation In a point-to-multipoint network, the base station is usually configured for protocol for-matting, unless the applications running on each remote can determine the data’s destina-tion from the data itself. Protocol formatting adds the address of the destination (remote) and other overhead bytes to the user data. If the addressed remote is using transparent for-matting, the destination address and the other overhead bytes are removed. If the remote is using protocol formatting, the destination address and the other overhead bytes are out-put with the user data. A remote can operate in a point-to-multipoint network using either transparent or proto-col formatting, as the base station is always the destination. In transparent operation, a remote will add addressing, a packet sequence number and error checking bytes as in a point-to-point network. When the base station receives the transmission, it will format the data to its host according to its formatting configuration. A remote running in transparent mode in a point-to-multipoint network will often have the MinPacketLength and TxTime-out parameters set to non-zero values to reduce the chance of transmission collisions. This is covered in more detail in section 2.6.3. 2.6 Full-Duplex Serial Data Communications From an host application’s perspective, DNT500 serial communications appear full du-plex. Both the base station host application and each remote host application can send and receive serial data at the same time. At the radio level, the base station and remotes do not actually transmit at the same time. If they did, the transmissions would collide. As discussed earlier, the base station transmits a synchronization signal at the beginning of each hop followed by its user data. After the base station transmission, the remotes can transmit. Each base station and remote transmission may contain all or part of a complete message from its host application. From an application’s perspective, the radios are communicating in full duplex since the base station can receive data from a remote before it completes the transmission of a message to the remote and visa versa. 2.7 Channel Access The DNT500 provides two methods of channel access: CSMA or TDMA. Each method supports several options as shown in the table below. The channel access setting is dis-tributed to all remotes in the base station status packet, so changing it at the base station sets the entire network. Carrier Sense Multiple Access (CSMA) is very effective at han-dling packets with varying amounts of data and/or packets sent at random times from a large number of remotes. The DNT500 includes a CSMA polling mode for coordinated remotes and a CSMA contention mode for uncoordinated and/or reporting remotes. Time Division Multiple Access (TDMA) provides a scheduled time slot for each remote to transmit on each hop. The default DNT500 access mode is CSMA polling.
DNT500  2008 by RF Monolithics, Inc. 8 M-0500-0000 Rev D Access Mode Description Max # of Remotes Remote Slot Size 0 CSMA polling 1024 manual 1 CSMA contention 1024 manual 2 (default) TDMA dynamic slots up to 15 automatic 3 TDMA fixed slots up to 15 automatic 4 TDMA with PTT 1024 automatic 2.7.1 CSMA Modes When using CSMA, each remote with data to send listens to see if the channel is clear and then transmits. If the channel is not clear, a remote will wait a random period of time and listen again. CSMA works best when a large or variable number of remotes transmit infrequent bursts of data. There is no absolute to the number of remote radios that can be supported in this mode. For a DNT500 network, a maximum of 255 remotes can be sup-ported if base station join-leave tracking is required, or a maximum of 1024 remotes is suggested if base station join-leave tracking is not required. The illustration below com-pares TDMA to CSMA operation. There are two important parameters related to CSMA operation. The CSMA_MaxBackoff parameter defines the maximum time that a remote will wait after a collision before at-tempting to send the packet again (back-off interval). The CSMA_Persistence parameter sets the probability that a remote will transmit immediately rather than first waiting for a pre-transmit delay interval. Persistence is a one-byte parameter with a range of 0x00 to 0xFF: 0xFF = 100% probability 0x00 = 0% probability CSMA polling (Mode 0) is used for point-to-point systems and point-to-multipoint sys-tems where only one remote at a time can receive data to transmit (ModBus, etc.). Since only one remote will attempt to transmits at a time, the CSMA_Persistence parameter is fixed at 0xFF for minimum latency. This mode provides maximum throughput since there is no contention between remotes and the entire portion of the hop frame following the base station transmission is available for a remote to transmit. The user can set
DNT500  2008 by RF Monolithics, Inc. 9 M-0500-0000 Rev D CSMA_MaxBackoff, BaseSlotSize and RemoteSlotSize parameters when using this mode. Note that a CSMA_Persistence parameter setting of 0xFF would lead to collisions if more than one remote tried to transmit. Applications where more than one remote can receive serial data to transmit at the same time, or where periodic reporting and/or event report-ing are enabled should not use this mode. CSMA Contention (Mode 1) provides classical CSMA channel access, and gives the user control over both the CSMA_MaxBackoff and CSMA_Persistence parameters. This mode is well-suited for large numbers of uncoordinated remotes, and/or where periodic/event reporting is used. In addition to CSMA_MaxBackoff and CSMA_Persistence, the user can set the BaseSlotSize and RemoteSlotSize parameters when using this mode. The following guidelines are suggested for setting CSMA_Persistence: • For lightly loaded CSMA contention networks, increase CSMA_Persistence to 0x80 or higher to reduce latency. • For heavily loaded CSMA contention networks, reduce CSMA_Persistence to 0x20 or lower for better throughput. CSMA modes can optionally track remotes entering and leaving the network for up to 255 remotes. The base station is operated in protocol mode and is configured to generate a CONNECT message for its host when a remote registers, and a DISCONNECT mes-sage when the remote’s registration lease expires. The base station in a CSMA network can generate CONNECT messages for more than 255 remotes. This allows the host application to track remotes entering and leaving a large CSMA network by creating a table of MAC addresses and periodically sending a ping to each remote in the table. Failure to answer the ping indicates the remote is no longer active in the network. The CSMA modes work well in many applications, but CSMA does have some limita-tions, as summarized below: • Bandwidth is not guaranteed to any remote. • Marginal RF links to some remotes can create a relatively high chance of collisions in heavily loaded networks. 2.7.2 TDMA Modes The TDMA modes provide guaranteed bandwidth to some or all of the remotes in the network. Remotes that register with the base station receive several special parameters, including ranging information and a specific channel access slot assignment. TDMA reg-istrations are always leased and must be renewed every 250 hops. The DNT500 provides three different modes of TDMA access, as discussed below. TDMA Dynamic Slots (Mode 2) is used for general-purpose TDMA applications where scaling the capacity per slot to the number of active remotes is automatic. Each remote that registers with the base receives an equal time slice. As new remotes join, the size of the TDMA slots shrink accordingly. The number of slots, individual slot start times, and
DNT500  2008 by RF Monolithics, Inc. 10 M-0500-0000 Rev D the RemoteSlotSize are computed automatically by the DNT500 network in this mode. The user should note that the bandwidth to each remote will change immediately as re-motes join and leave the network. TDMA Fixed Slots (Mode 3) is used for applications that have fixed data throughput re-quirements, such as isochronous voice or streaming telemetry. The slot start time and the RemoteSlotSize are computed automatically by the DNT500 network in this mode. The user must set the number of slots. TDMA with PTT (Mode 4) supports remotes with a "push-to-talk" feature, also referred to as "listen-mostly" remotes. This mode uses fixed slot allocations. Remotes can be reg-istered for all but the last slot. The last slot reserved for the group of remotes that are usu-ally listening, but occasionally need to transmit. In essence, the last slot is a shared chan-nel for this group of remotes. When one of them has data to send it keys its transmitter much like a walkie-talkie, hence the name push-to-talk (PTT). The slot start time and the RemoteSlotSize are computed automatically by the DNT500 network in this mode. The user must specify the number of slots. The last slot is reserved for the PTT remotes. The user must configure PTT remotes individually to select Mode 4 operation. The network makes no guarantee that PTT remote transmissions will not col-lide in the shared slot. The user's application must ensure that no more than one PTT re-mote is using the slot at a time. 2.7.3 Network Configuration Planning Some planning is necessary for a DNT500 network to coordinate the RF_DataRate, HopDuration, BaseSlotSize, RemoteSlotSize, MinPacketLength, TxTimeout and TDMA_MaxNumSlots parameters to achieve a practical configuration. This is true even for modes that automatically compute some of these parameters. Each parameter has a limited range of usable values, as shown in the table below: Parameter Useable Range Value RF_DataRate 0..3 500, 200, 115.2 and 38.4 kb/s HopDuration 40..4095 2..204.75 ms (0.05 ms/count) TDMA_MaxNumSlots 1..15 max number of TDMA slots (MNS) for remotes BaseSlotSize 6..232 max number of user data bytes transmitted per hop RemoteSlotSize 3..243 max number of user data bytes transmitted per hop MinPacketLength 0..255 0..255 bytes TxTimeOut 0..255 0..255 ms (1 ms/count) The highest RF data rate, 500 kb/s, provides the highest throughput and the most flexibil-ity with respect to the other parameters. The maximum RF power that can be used at 500 kb/s is 19 dBm. The three lower data rates can run up to 28 dBm of RF power, and the receiver becomes progressively more sensitive as the data rate is lowered. So for greatest operating range, one of the three lower RF data rates should be used. The maximum DNT500 HopDuration setting is about 200 ms regardless of the RF data rate chosen. For a given data rate, FHSS operation tends to become more robust as hop duration is reduced. However, running with a shorter hop duration may require setting the
DNT500  2008 by RF Monolithics, Inc. 11 M-0500-0000 Rev D BaseSlotSize and RemoteSlotSize parameters well below their maximum values at the lower RF data rates. The equation below calculates the minimum hop duration needed at a given RF data rate for a specific number of remote slots and BaseSlotSize and Re-moteSlotSize parameter settings. Support for optimizing a DNT500 configuration for a specific application is also available from RFM’s Technical Support Group. See Section 10.3. for technical support contact information. The minimum required hop duration for a DNT500 configuration is: THD = TBRO + NRS*TRO + TRFB*(BBSS + NRS*BRSS) Where: THD is the minimum required hop duration in milliseconds TBRO is the base and registration request overhead time for each hop (RF data rate dependent) NRS is the number of remote slots TRO is the remote overhead time for each hop (RF data rate dependent) TRFB is the transmission time for one user byte (RF data rate dependent) BBSS is the BaseSlotSize parameter in bytes BRSS is the RemoteSlotSize parameter in bytes The constants in the equation for each RF data rate are given in the following table: RF Data Rate kb/s TBRO ms TRO ms TRFB ms 38.40 11.620 4.817 0.2080 115.2 4.953 2.039 0.0694 200 3.540 1.450 0.0400 500 2.388 0.970 0.0160 For Example 1, consider a point-to-point CSMA Mode 0 system operating at 38.4 kb/s with the BaseSlotSize parameter set to 133 bytes and the RemoteSlotSize parameter set to 128 bytes. The minimum hop duration needed to support one-hop transmissions of full slot size messages in both directions for this configuration is: = 11.620 + 1*4.817 + 0.2080*(133 + 1*128) = 16.437 + 0.2080*261 = 70.725 ms The closest programmable hop duration is 70.750 ms. It should be noted that the base station operating system will commandeer 5 bytes from the BaseSlotSize allocation in Mode 0 and up to 13 bytes in Mode 1 to send reception ac-knowledgements (ACKs) back to the remotes. The BaseSlotSize should be sized accord-ingly. In the above example, the BaseSlotSize parameter is set five bytes larger than the RemoteSlotSize parameter to accommodate the ACK bytes. When running a point-to-multipoint network with uncoordinated remotes using CSMA Mode 1, it is useful to set NRS to a value of 3 or higher in the equation. Although CSMA
DNT500  2008 by RF Monolithics, Inc. 12 M-0500-0000 Rev D does not create reserved time slots for remotes, extending the hop duration this way al-lows several uncoordinated transmissions of user data and/or periodic/event reports to ar-rive in the same slot with a relatively few collisions. The performance of a CSMA Mode 1 system can often be helped by setting the Min-PacketLength and TxTimeout parameters on any remotes running transparent mode to non-zero values, especially if host messages only contain a few bytes each and transmis-sion latency is not critical. For starting point values, set the MinPacketLength equal to the RemoteSlotSize and TxTimeout to at least three times the hop duration. This will help avoid excessive transmission collisions due to having many packets transmitted, each car-rying only a small amount of user data on top of the relatively large packet overhead structure. For Example 2, consider a TDMA Mode 2 or 3 system operating at 500 kb/s. Up to 10 registered remotes need to be accommodated. A BaseSlotSize of 138 bytes is needed, and each remote needs enough slot time to support a RemoteSlotSize of 64 bytes. The mini-mum hop duration needed to support this configuration is: = 2.388 + 10*0.970 + 0.0160*(138 + 10*64) = 12.088 + 0.0160*778 = 24.536 ms The closest programmable hop duration is 24.550 ms. In all TDMA modes, the base station operating system will commandeer one byte from the BaseSlotSize allocation for each registered remote to send ACKs to the remotes. The BaseSlotSize and MinPacketLength should be sized accordingly. 2.7.4 Serial Port Operation DNT500 networks are often used for wireless communication of serial data. The DNT500 supports serial baud rates from 1.2 to 460.8 kb/s. Listed in the table below are the supported data rates and their related byte data rates and byte transmission times for an 8N1 serial port configuration: Baud Rate kb/s Byte Data Rate kB/s Byte Transmission Time ms 1.2 0.12 8.3333 2.4 0.24 4.1667 4.8 0.48 2.0833 9.6 0.96 1.0417 19.2 1.92 0.5208 38.4 3.84 0.2604 115.2 11.52 0.0868 230.4 23.04 0.0434 460.8 46.08 0.0217 To support continuous full-duplex serial port data flow, an RF data rate much higher than the serial port baud rate is required for FHSS. Radios transmissions are half duplex, and
DNT500  2008 by RF Monolithics, Inc. 13 M-0500-0000 Rev D there are overheads related to hopping frequencies, assembling packets from the serial port data stream, transmitting them, sending ACK’s to confirm error-free reception, and occasional transmission retries when errors occur. For Example 3, consider a CSMA Mode 0 transparent data system operating at 500 kb/s with the BaseSlotSize parameter set to 133 bytes (128 bytes net after the five byte alloca-tion for sending ACKs) and the RemoteSlotSize parameters set to 128 bytes. The mini-mum hop duration needed to efficiently support this configuration is: = 2.388 + 1*0.970 + 0.0160*(133 +1*128) = 3.358 + 0.0160*261 = 7.534 ms Setting the hop duration to 7.55 ms, the average full-duplex serial port byte rate that can be supported under error free conditions is: 128 Bytes /7.55 ms = 16.942 kB/s, or 169.42 kb/s for 8N1 Continuous full-duplex serial port data streams at a baud rate of 115.2 k/bs can be sup-ported by this configuration, provided only occasional RF transmission errors occur. Plan on an average serial port data flow of 75% of the calculated error-free capacity for gen-eral-purpose applications, and 50% of the calculated error-free capacity for RF challeng-ing applications such as vehicle telemetry and heavy industrial process environments. Most applications do not require continuous serial port data flow. The DNT500 transmit and receive buffers hold at least 1024 bytes and will accept brief bursts of data at high baud rates, provided the average serial port data flow such as shown in Example 3 is not exceeded. It is strongly recommended that the DNT500 host use hardware flow control. The host must send no more than 32 bytes additional bytes to the DNT500 when the DNT500 de-asserts the hosts CTS line. In turn, the DNT500 will send no more than one byte following the host de-asserting its RTS line. Three-wire serial port operation is al-lowed by connecting the DNT500 CTS output to its RTS input. However, three-wire op-eration should be limited to applications that send small bursts of data occasionally at an average serial port data flow less than 50% of the calculated error-free capacity. Data loss is possible under adverse RF channel conditions when using three-wire serial operation. 2.7.5 Sleep Mode To save power in applications where a remote transmits infrequently, the DNT500 sup-ports a Sleep Mode. Sleep Mode is entered by switching DTR Pin 11 on the DNT500 from logic low to high. While in Sleep Mode, the DNT500 consumes less than 0.5 mA. This mode allows a DNT500 to be powered off while its host device remains powered. After leaving Sleep Mode (Pin 11 low to high), the radio must re-synchronize with the base station and re-register.
DNT500  2008 by RF Monolithics, Inc. 14 M-0500-0000 Rev D 3. DNT500 HARDWARE 2 3 2 4 2 5 2 6 2 7 2 82 22 1 2 9 3 0 3 11 81 71 61 51 41 31 21 11 098765D N T 5 0 0 B l o c k D i a g r a m3 2 3 3 3 4 3 6M i c r o c o n t r o l l e r4321R e gF i l t e rF i l t e rV C CP W M AP W M BG P I O 0G P I O 1G P I O 2G P I O 3G N D4 2R a d i oC L KI N TC S n R F I OG N DU A R T 0 _ R X DU A R T 0 _ T X D/ R E S E TS P I _ N S SS P I _ M O S IS P I _ M I S OT / RT / RP W RP R EF i l t e r3 54 14 31 92 03 7 3 8 3 9 4 0S IS OP K T D E TR e g3 . 3 V3 . 6 VR S V DR S V DA D C _ R E FR S S ID T RA D C XA D C YA D C ZE X _ S Y N CU A R T 1 _ R X DU A R T 1 _ T X DC F GU A R T 0 _ R T SU A R T 0 _ C T SG P I O 4G P I O 5R S V DA C TD C DR S V DR S V DR S V DV M O DS P I _ S C L KB O O T _ L O A D The major components of the DNT500 include a 900 MHz FHSS transceiver and a 32-bit microcontroller. The DNT500 operates in the frequency band of 902 to 928 MHz. There are 32 selectable hopping patterns including patterns compatible the frequency alloca-tions in the US, Canadian, Australian and New Zealand. The DNT500 has six selectable RF output power levels: 0, 10, 19, 24, 27 and 28 dBm. Also, there are four selectable RF transmission rates: 38.4, 115.2, 200 and 500 kb/s. The power level is firmware inter-locked to a maximum of 19 dBm at 500 kb/s to assure regulatory compliance. The DNT500 includes a low-noise preamplifier protected by two SAW filters, providing an excellent blend of receiver sensitivity and out-of-band interference rejection. The DNT500 provides a variety of hardware interfaces. There are two UART serial ports, one for data and a second for diagnostics. The data port supports baud rates from 1.2 to 460.8 kb/s and the diagnostic port supports baud rates from 38.4 to 460.8 kb/s. Other hardware interfaces include an SPI interface, three 10-bit ADC inputs, two 8-bit resolu-tion PWM (DAC) outputs, and six general purpose digital I/O ports. Four of the digital I/O ports support an optional interrupt-from-sleep mode when configured as inputs. A 3.6 Vdc signal can be switched on the RF output port for diversity antenna control. The radio is available in two mounting configurations. The DNT500 is designed for solder re-flow mounting. The DNT500P is designed for plug-in connector mounting.
DNT500  2008 by RF Monolithics, Inc. 15 M-0500-0000 Rev D 3.1 Specifications The DNT500 specifications are listed in the table below: Characteristic Sym Notes Minimum Typical Maximum Units Operating Frequency Range 902.75 927.25 MHz FCC 15.247 FHSS 1 38.4, 115.2 and 200 kb/s, up to 28 dBm FCC 15.247 Digital Modulation (DSS) 1 500 kb/s, up to 19 dBm Number of Hopping Patterns 32 Hop Dwell Time 5 200 ms Number of RF Channels 50 RF Data Transmission Rates 1 38.4, 115.2, 200 and 500 kb/s Receiver Sensitivity 10-5 BER @ 38.4 kb/s -108 dBm 10-5 BER @ 500 kb/s -94 dBm Transmitter RF Output Power Levels 1 0, 10, 19, 24, 27, 28 dBm Optimum Antenna Impedance 50 Ω RF Connection U.FL Connector or PCB Pad Network Topologies Point-to-Point, Point-to-Multipoint, Mesh Access Schemes TDMA and CSMA Number of Network Nodes TDMA 15 CSMA 1024 ADC Input Range 0 3.3 V ADC Input Resolution 10 bits Signal Source Impedance for ADC Reading 10 KΩ PWM (DAC) Output Range 0 3.3 V PWM (DAC) Output Resolution 8 bits Primary Serial Port Baud Rates 1.2, 2.4, 4.8, 9.6, 19.2, 38.4, 115.2, 230.4, 460.8 kb/s Diagnostic Serial Port Baud Rates 38.4, 115.2, 230.4, 460.8 kb/s Digital I/O: Logic Low Input Level -0.5 0.8 V Logic High Input Level 2 3.3 V Logic Input Internal Pull-up Resistor 50 200 KΩ Logic Input Internal Pull-down Resistor 50 180 KΩ Power Supply Voltage Range VCC +3.3 +5.5 Vdc Power Supply Voltage Ripple 10 mVP-P Receive Mode Current 50 mA Transmit Mode Current 900 mA DTR High Sleep Current 0.5 mA Operating Temperature Range -40 85 oC Operating Relative Humidity Range 10 90 % 1. RF output power is interlocked in firmware to a maximum of 19 dBm at the 500 kb/s RF data rate to assure compliance with regulatory requirements.
DNT500  2008 by RF Monolithics, Inc. 16 M-0500-0000 Rev D 3.2 Module Interface Electrical connections to the DNT500 are made through the I/O pads and through the I/O pins on the DNT500P. The hardware I/O functions are detailed in the table below: Pad Name Description 1 RSVD Reserved pad. Leave unconnected. 2 RSVD Reserved pad. Leave unconnected. 3 ADC_REF ADC supply and external full scale reference voltage input. Voltage range is 2.4 to 3.3 Vdc. Connect pad 34 to this input to reference the ADC full scale reading to the module’s 3.3 V regulated supply. 4 RSSI Analog voltage proportional to received signal strength, range 0 to 3.3 V. 5 GPIO0 Configurable digital I/O port 0. When configured as an input, an internal pull-up resistor can be selected and interrupt from sleep can be invoked. When configured as an output, the power-on state is also configurable. 6 GPIO1 Configurable digital I/O port 1. Same configuration options as GPIO0. 7 GPIO2 Configurable digital I/O port 2. Same configuration options as GPIO0. 8 GPIO3 Configurable digital I/O port 3. Same configuration options as GPIO0. 9 PWM0 Pulse-width modulated output 0 with internal low-pass filter. Provides an 8-bit DAC resolution. 10 PWM1 Pulse-width modulated output 1 with internal low-pass filter. Provides an 8-bit DAC resolution. 11 SLEEP Default functionality is active high module sleep input. When switched low after sleep, the module executes a power-on reset. 12 ADC0 10-bit ADC input 0. Full scale reading is referenced to the ADC_REF input. 13 ADC1 10-bit ADC input 1. Full scale reading is referenced to the ADC_REF input. 14 ADC2 10-bit ADC input 2. Full scale reading is referenced to the ADC_REF input. 15 EX_SYNC Optional rising-edge triggered input for synchronizing co-located base stations. See External-SyncEn on Page 25 for additional details. 16 DIAG_TX Diagnostic output (for factory use). 17 DIAG_RX Diagnostic input (for factory use). 18 /CFG Protocol selection input. Leave unconnected when using software commands to select trans-parent/protocol mode (default is transparent mode). Logic low selects protocol mode, logic high selects transparent mode. 19 VCC Power supply input, +3.3 to +5.5 Vdc. 20 GND Power supply and signal ground. Connect to the host circuit board ground. 21 GND Power supply and signal ground. Connect to the host circuit board ground. 22 GPIO4 Configurable digital I/O port 4. When configured as an input, an internal pull-up resistor can be selected. When configured as an output, the power-on state is configurable. 23 GPIO5 Configurable digital I/O port 5. Same configuration options as GPIO4. 24 RSVD Reserved pad. Leave unconnected. 25 ACT Data activity output, logic high when data is being transmitted or received. 26 /DCD Default functionality is data carrier detect output, which provides a logic low on a remote when the module is locked to FHSS hopping pattern and logic low on a base station when at least one remote is connected to it.
DNT500  2008 by RF Monolithics, Inc. 17 M-0500-0000 Rev D Pad Name Description 27 RSVD Reserved pad. Leave unconnected. 28 RSVD Reserved pad. Leave unconnected. 29 RSVD Reserved pad. Leave unconnected. 30 /UART0_RTS Default functionality is UART flow control input for the module’s host. A logic low allows data flow from the module to the host; a logic high blocks data flow from the module to the host. 31 UART0_RXD UART received data output to host from module. 32 UART0_TXD UART host data input to be transmitted by module. 33 /UART0_CTS UART flow control output from the module to the host. A logic low should allow data flow from the host; a logic high should block data flow from the host. 34 VMOD Module’s +3.3 V regulated supply output. Connect to pad 3 to support 3.3 V full scale and/or ratiometric ADC readings, etc. Current drain on this output should be no greater than 5 mA. 35 SPI_NSS Active low SPI enable (slave). This input must be held low for the duration of an SPI transmis-sion. 36 SPI_MOSI SPI port data output. 37 SPI_MISO SPI port data input. 38 SPI_SCLK SPI port clock signal. 39 /RESET Active low module hardware reset. 40 BOOT_LOAD Logic high at power up enables module boot loader. Hold low for normal operation. 41 GND RF ground (DNT500 only). Connect to the host circuit board ground plane. 42 RFIO Alternate RF port to the U.FL connector (DNT500 only). The antenna can be connected to this port with a 50 Ω stripline or coaxial cable. Leave unconnected when using the U.FL connector. 43 GND RF ground (DNT500 only). Connect to the host circuit board ground plane. 3.3 Input Voltages DNT500 radio modules can operated from an unregulated DC input (Pad/Pin 19) in the range of 3.3 (trough) to 5.5 V (peak) with a maximum ripple of 5% over the temperature range of -40 to 85 C. Applying AC, reverse DC, or a DC voltage outside the range given above can cause damage and/or create a fire and safety hazard. Further, care must be taken so logic inputs applied to the radio stay within the voltage range of 0 to 3.3 V. Sig-nals applied to the analog inputs must be in the range of 0 to ADC_REF(Pad/Pin 3). Ap-plying a voltage to a logic or analog input outside of its operating range can damage the DNT500 module. 3.4 ESD and Transient Protection The DNT500 and DNT500P circuit boards are electrostatic discharge (ESD) sensitive. ESD precautions must be observed when handling and installing these components. In-stallations must be protected from electrical transients on the power supply and I/O lines. This is especially important in outdoor installations, and/or where connections are made to sensors with long leads. Inadequate transient protection can result in damage and/or create a fire and safety hazard.
DNT500  2008 by RF Monolithics, Inc. 18 M-0500-0000 Rev D 3.5 Interfacing to 5 V Logic Systems All logic signals including the serial ports on the DNT500 are 3.3 V signals. To interface to 5 V signals, the resistor divider network shown below must be placed between the 5 V signal outputs and the DNT500 signal inputs. The output voltage swing of the DNT500 3.3 V signals is sufficient to drive 5 V logic inputs. 5 VL o g i c D N T 5 0 02 . 2 K4 . 3 K 3.6 Power-On Reset Requirements The DNT500 has an internal reset circuit that generates and maintains the DNT500 in a reset state until the power supply voltage reaches 3.3 volts for 100 milliseconds. This re-set circuit protects the radio and non-volatile memory from brown-out voltage conditions. If devices that communicate with the DNT500 have shorter reset periods, an allowance must be made to allow the DNT500 to come out of reset. Commands and data sent before the DNT500 is out of reset will be ignored. 3.7 Analog RSSI Output Pin 4 on the DNT500 provides a 0.3 to 3.0 V output proportional to received signal strength in dB, as follows: VRSSI = 0.03*SRF + 3.6 Where: VRSSI is the RSSI output in volts, over the range of 0.3 to 3.0 V SRF is the RF signal strength in dBm, over the range of -110 to -20 dBm The analog RSSI output on a DNT500 remote represents the signal strength of the last base station transmission received. The RSSI output on a base station represents the sig-nal strength of the last remote transmission heard. 3.8 Mounting and Enclosures DNT500 radio modules are mounted by reflow soldering them to a host circuit board. DNT500P modules are mounted by plugging their pins into a set of mating connectors on the host circuit board. Refer to the DNT500 data sheet for a suitable solder reflow profile and details of the connectors for the DNT500P. DNT500 radio module enclosures must be made of plastics or other materials with low RF attenuation to avoid compromising antenna performance. Metal enclosures are not suitable as they will block antenna radiation and reception. Outdoor enclosures must be water tight, such as a NEMA 4X enclosure.
DNT500  2008 by RF Monolithics, Inc. 19 M-0500-0000 Rev D 3.9 Connecting Antennas A U.FL miniature coaxial connector is the primary RF connection point on the DNT500, and the only RF connection point on the DNT500P. On the DNT500, it is also possible to connect an antenna using a stripline from pad 42 instead of the U.FL connector. It is im-portant that this connection be implemented as a 50 ohm stripline trace. A short coaxial jumper cable should be used to connect to between the U.FL connector on the DNT500P and the host circuit board U.FL connector. The host PCB U.FL connector should connect to the antenna or antenna connector with a 50 ohm stripline trace. The design details of the stripline are covered in the DNT500 Data Sheet. 3.10 Labeling and Notices DNT500 FCC Certification - The DNT500 hardware has been certified for operation un-der FCC Part 15 Rules, Section 15.247. The antenna(s) used for this transmitter must be installed to provide a separation distance of at least 20 cm from all persons and must not be co-located or operating in conjunction with any other antenna or transmitter. DNT500 FCC Notices and Labels - This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions: (1) this device may not cause harm-ful interference, and (2) this device must accept any interference received, including in-terference that may cause undesired operation. A clearly visible label is required on the outside of the user’s (OEM) enclosure stating that this product contains a DNT500 transceiver assembly, FCC ID: HSW-DNT500P. WARNING: This device operates under Part 15 of the FCC rules. Any modification to this device, not expressly authorized by RFM, Inc., may void the user’s authority to oper-ate this device. Canadian Department of Communications Industry Notice - IC: 4492A-DNT500P This apparatus complies with Health Canada’s Safety Code 6 / IC RSS 210. ICES-003 This digital apparatus does not exceed the Class B limits for radio noise emissions from digital apparatus as set out in the radio interference regulations of Industry Canada. Le present appareil numerique n’emet pas de bruits radioelectriques depassant les limites applicables aux appareils numeriques de Classe B prescrites dans le reglement sur le brouillage radioelectrique edicte par Industrie Canada.
DNT500  2008 by RF Monolithics, Inc. 20 M-0500-0000 Rev D 4. PROTOCOL MESSAGES 4.1 Protocol Message Formats The DNT500 is configured and controlled through a series of protocol mode messages. All protocol mode messages have a common header format: 0 1 2 3 … N SOP Length PktType variable number of arguments … LRC* The scale above is in bytes. General comments: • The Start-of-Packet (SOP) character, 0xFB, is used to distinguish the beginning of a message and to assure synchronization in the event of a glitch on the serial port at startup. • The Length byte is defined as the length of the remainder of the message following the length byte itself (or the length of the entire message - 2). If the LRC is enabled, it is included in the length. • The Packet Type (PktType) byte specifies the type of message. It is a bitfield-oriented specifier, decoded as follows: Bits 7-6 Reserved for future use Bit 5 Event - set to indicate this message is an event Bit 4 Reply - set to indicates this message is a reply Bits 3-0 Type - indicates the message type/command As indicated, the lower 4 bits (3-0) specify a message type. Bit 4 is a modifier indicat-ing that the message is a command or a reply. A reply message has the original com-mand type in bits 3:0, with bit 4 set to one. • Arguments vary in size and number depending on the type of message and whether it is a message sent from the host or is a reply from the radio; see the table provided be-low for reference. • The LRC is an optional checksum byte that verifies the integrity of the message re-ceived. It is the two's complement of the sum of all the bytes in the message. If the sum is larger than 1 byte, only the LSB is used. For example, 0xFB 0x05 0x04 0x01 0x0A 0x00 0x01 → LRC = 0xF0. Messages that are generated on the serial interface by the user are referred to as host messages. Messages that are generated by the radio are referred to as reply messages. For many message types, there is a reply message that corresponds to a host message. For example, when the host sends a TxData message, the radio will reply to indicate the status of the transmission, whether it succeeded or failed. Some message types are host-only or reply-only; please refer to the table for specifics. 4.1.1 Serial message types Each message generally has two forms, a command from the host and a reply from the radio. Depending on the direction, they have different arguments as shown in the table
DNT500  2008 by RF Monolithics, Inc. 21 M-0500-0000 Rev D below. Event messages from the radio such as receive data packets or status announce-ments make up a third category of messages. To assist in interpreting the command-reply data flow, the direction is indicated by Bit 4 in the message type. For example, an Enter-ProtocolMode command from the host is message type 0x00, and the EnterProtocol-ModeReply from the radio is message type 0x10. Event messages, including RxData, RxEvent and ANNOUNCE, packets are indicated by setting Bit 5 high in the type byte. If multiple arguments are to be provided, they are to be concatenated in the order shown. Little-Endian byte format is used for all multi-byte arguments, where the lowest order byte is the left byte of the argument and the highest order byte in the right byte of the ar-gument. Message Type Code Com-mand Reply Event Description Direction Arguments 0x00 - - EnterProtocolMode from Host "DNT500" - 0x10 - EnterProtocolModeReply from Radio none 0x01 - - ExitProtocolMode from Host none - 0x11 - ExitProtocolModeReply from Radio none 0x02 - - SoftwareReset from Host BootSelect - 0x12 - SoftwareResetReply from Radio none 0x03 - - GetRegister from Host Reg, Bank, Span - 0x13 - GetRegisterReply from Radio Reg, Bank, Span,Val 0x04 - - SetRegister from Host Reg, Bank, Span, Val - 0x14 - SetRegisterReply from Radio none 0x05 - - TxData from Host Addr, Data - 0x15 - TxDataReply from Radio TxStatus, Addr, RSSI - - 0x26 RxData from Radio Addr, RSSI, Data - - 0x27 Announce from Radio AnnStatus, add'l fields - - 0x28 RxEvent from Radio Addr, RSSI, Reg, Bank, Span,Val 0x0A - - GetRemoteRegister from Host Addr, Reg, Bank, Span - 0x1A - GetRemoteRegisterReply from Radio TxStatus, Addr, RSSI, Reg, Bank, Span, Val* 0x0B - - SetRemoteRegister from Host Addr, Reg, Bank, Span, Val - 0x1B - SetRemoteRegisterReply from Radio TxStatus, Addr, RSSI - - 0x2F Instrumentation from Radio DiagInfo *If TxStatus is non-zero in a GetRemoteRegisterReply, the Reg, Bank, Span and Val bytes will not be present in the message Arguments: Reg = Register location (1 byte). Bank = Register bank, which provides logical isolation from other data regions (1 byte). Span = Number of bytes of register data to get or set; must align to a parameter boundary (1 byte). Val = Value to read/write to/from register (see table for size and acceptable range).
DNT500  2008 by RF Monolithics, Inc. 22 M-0500-0000 Rev D Data = User data (variable size, 0 to 128 bytes). Addr = MAC address of the sender for a reply or event, or recipient for a command (3 bytes). TxStatus = Result of last TxData operation (1 byte). 0 = Acknowledgement received. 1 = No acknowledgement received. 2 = (Remote) Not linked. 3 = Recipient holding for flow control. RSSI = RSSI, range 0x01 to 0xFE. Values 0x00 & 0xFF have special meanings (1 byte). 0x00 = No RSSI measured because no ACK was received. 0xFF = No RSSI measured because packet was relayed. NwkID = Network identifier of network joined (1 byte). BaseMacAddr = MAC address of base that the remote joined (3 bytes). BootSelect = Code indicating whether to do a normal reset or a reset to the bootloader (1 byte). (0 = normal reset, 1 = reset to bootloader) AnnStatus = Status announcement (1 byte). Additional fields are also reported depending on the status code: Status code Add'l fields A0 = Radio has completed startup initialization. none A1 = Base: Network formed, ready for data. NwkID A2 = Base: A remote has joined me. MacAddr (0xFF if none) A3 = Remote: Joined a network, ready for data. NwkID, BaseMacAddr, Range A4 = Remote: Exited network (base is out of range). NwkID A5 = Remote: Base has restarted. none A7 = Base: Remote has left the network. Addr Status codes for error conditions Add'l fields E0 = Protocol error -- invalid message type. none E1 = Protocol error -- invalid argument. none E2 = Protocol error -- general error. none E3 = Protocol error -- parser timeout. none E4 = Protocol error -- register is read-only. none E8 = UART receive buffer overflow. none E9 = UART receive overrun. none EA = UART framing error. none JoinAddr = MAC address of radio joining (3 bytes). Range = Range measurement of radio joining. (1 byte). 4.1.2 Escape sequence The escape sequence is a sequence of bytes that the user can input in transparent mode to switch the radio to configuration mode. In the DNT500, we define the EnterProtocol-Mode command as the ASCII escape sequence “DNT500” (quotation marks are not part of the sequence). A radio that is already in protocol mode will respond to this command the same way as a radio that is in transparent mode. For the escape sequence to be recog-nized, byte flow must pause at least 20 ms before the escape sequence is sent.
DNT500  2008 by RF Monolithics, Inc. 23 M-0500-0000 Rev D 4.1.3 CFG select pin A falling edge on the CFG pin is the equivalent of entering the escape sequence to invoke the protocol mode. A rising edge on the CFG pin is the equivalent to sending the exit pro-tocol command. 4.1.4 Flow control There are two flow control signals between the radio and the host, RTS and CTS. See Section 2.7.4 for flow control details. 4.1.5 Protocol mode data message example For Example 4, ASCII text “Hello World” is sent from the base station to a remote using a TxData command. The MAC address of the remote is 0x000102. The protocol format-ting for the host message is: 0xFB 0x0F 0x05 0x02 0x01 0x00 0x48 0x65 0x6C 0x6C 0x6F 0x20 0x57 0x6F 0x72 0x6C 0x64 There are 15 bytes following the length byte, so the length byte is set to 0x0F. Note that the 0x000102 MAC address is entered in Little-Endian byte order 0x02 0x01 0x00. When an ACK to this message is received from the remote, the base station outputs a TxDataReply message to its host: 0xFB 0x06 0x15 0x00 0x02 0x01 0x00 0x80 The 0x00 TxStatus byte value indicates the ACK reception from the remote. The RSSI value is 0x80. If the remote is in protocol mode, the received message is output in the following format: 0xFB 0x10 0x26 0x02 0x01 0x00 0x8A 0x48 0x65 0x6C 0x6C 0x6F 0x20 0x57 0x6F 0x72 0x6C 0x64 The message is output as an 0x26 event. Note that the RSSI value 0x8A is inserted be-tween the remote’s MAC address and the “Hello World” user data. 4.2 Configuration Registers The configuration registers supported by the DNT500 are described below. Registers are sorted into banks according to similarity of function.
DNT500  2008 by RF Monolithics, Inc. 24 M-0500-0000 Rev D 4.2.1 Bank 0 - Transceiver Setup Size in Bank Loc'n Name R/W bytes Range Default, Options 00 00 DeviceMode R/W1 1 0..2 0 = Remote, 1= Base, 2 = PTT Remote 00 01 RF_DataRate R/W 1 0..4 0 = 500, 1 = 200, 2 = 115.2, 3 = 38.4 kb/s, 0xFF = auto 00 02 HopDuration R/W 2 4..4000 10 ms (0x00C8) 00 04 InitialNwkID R/W 1 0..255 0xFF = broadcast 00 05 SecurityKey R/W 16 0..2128 0 = security disabled 00 15 SleepMode R/W 1 0..1 0 = off, 1 = timer, 2 = interrupt 00 16 SleepInterval R/W 2 0..216 0 = off 00 18 TxPower R/W 1 0..5 1 = 10 dBm; 0 = 1, 2 = 19, 3 = 24, 4 = 27, 5 = 28 dBm 00 19 ExternalSyncEn R/W 1 0..1 0 = disabled, 1 = input, 2 = output 00 1A DiversityMode R/W 1 0..1 0 = 0 V 00 1B JoinPermit R/W 1 0..1 0 = no join, 1 = remotes (default), 2 =any 00 1C UserTag R/W 16 "DNT500" Note: These settings are individual to each module. DeviceMode Selects the operating mode for the radio: remote, base, or PTT remote (listen mostly re-mote). Note that the setting takes effect immediately. RF_DataRate This sets the over-the-air RF data rate. Radios with different RF rates cannot intercom-municate. The following codes are defined: 0x00 = 500 kb/s 0x01 = 200 kb/s 0x02 = 115.2 kb/s 0x03 = 38.4 kb/s 0xff = auto (default) A setting of "auto" will cause a remote to scan all 4 possible RF rates for a network to join. A base set to "auto" will run at the maximum rate of 500 kb/s. A change to this set-ting on the base will trigger an epoch change to reboot the network. HopDuration This sets the duration of the hop frame. The duration is set as a 12-bit value, 0.05 ms/count. InitialNwkID Selects the initial network ID that the radio will start (if a base) or join (if a remote). A value of 0xFF instructs a remote to operate in 'promiscuous mode' and join any network it finds (if set for a base, this will select the default network of 0x00.) The network ID also sets the base frequency at which the hopping pattern starts, as illustrated by the following equation:
DNT500  2008 by RF Monolithics, Inc. 25 M-0500-0000 Rev D FrequencyIndex[n] = HoppingPattern[n + 2*NetworkID mod 32] This allows the user to coordinate frequency spacing of co-located networks to maintain a constant separation as they hop. SecurityKey This sets the 128-bit AES encryption key that will be used. The intent is for this to act like a password that all radios in the network are configured with. To protect the key, this is a write-only parameter for the user, unless the manufacturing write enable is set, in which case it is also readable. Refer to the section on Encryption for further information. SleepMode Sets the sleep mode. SleepInterval Sets the sleep interval as the number of superframes that a remote will sleep between wake intervals. A superframe interval is 64 hops. TxPower Sets the transmit power level: 0 = 0 dBm or 1 mW 1 = 10 dBm or 10 mW (default) 2 = 19 dBm or 79.4 mW 3 = 24 dBm or 250 mW 4 = 27 dBm or 500 mW 5 = 28 dBm or 1000 mW (1 W) When the data rate is set to 500 kb/s, the firmware interlocks the transmit power level to 19 dBm or less to comply with FCC regulations. ExternalSyncEn Enables the external sync input. This option allows a base radio's hopframes to be trig-gered by an external synchronization signal. Valid settings are 0 = disabled, 1 = sync pin is input, 2 = sync pin is an output. This last mode allows a base radio to source the sync signal for another radio. DiversityMode The DNT500 supports the following diversity antenna switching options: 0 = 0 V on the diversity pin (default) 1 = 3.3 V on the diversity pin 2 = 0 - 3.3 V toggle on every hop frame
DNT500  2008 by RF Monolithics, Inc. 26 M-0500-0000 Rev D JoinPremit Valid parameter on a base only. Controls whether remote nodes are permitted to join the base. Parameter values are 0 = no joining permitted, 1 = remotes only may join, 2 = re-motes or routers may join (future function). UserTag This is a user definable field intended for use as a location description or other identify-ing tag such as a “friendly name”. 4.2.2 Bank 1 - System Settings Size in Bank Loc'n Name R/W bytes Range Default; Options 01 00 FrequencyBand R/W 1 0..1 0x00 = North America; 0x01 = Australia, 0xFF = auto 01 01 AccessMode R/W 1 0..4 2 = TDMA Dynamic Slots 01 02 BaseSlotSize R/W 1 6..232 20 bytes 01 03 LeasePeriod R/W 1 0..250 5 s (0 to disable) 01 04 ARQ_Mode R/W 1 0..1 0 = ARQ, 1 = redundant TX 01 05 ARQ_AttemptLimit R/W 1 0..16 5 attempts 01 06 TDMA_MaxSlots R/W 1 0..15 8 slots 01 07 CSMA_Persistence R/W 1 0..255 0xFF 01 08 CSMA_MaxBackoff R/W 1 0..255 5 ms 01 09 MaxPropDelay R/W 1 0..255 50 µs (~4 miles) 01 0A EpochMode R/W 1 0..1 0 = use previous; 1 = increment 2 = random Note: The base station propagates these setting to all remotes. FrequencyBand This sets the range of frequencies over which the radio will operate. Two settings are de-fined: North America (902-928 MHz) and Australia-New Zealand (915-928 MHz). AccessMode This sets the channel access mode that remotes will use to communicate with the base: Access Mode Description Max # of Remotes Remote Slot Size 0 CSMA polling 1024 manual 1 CSMA contention 1024 manual 2 (default) TDMA dynamic slots up to 15 automatic 3 TDMA fixed slots up to 15 automatic 4 TDMA with PTT 1024 automatic BaseSlotSize This sets the size of the base slot. This number is specified in terms of the number of ap-plication payload bytes that can be supported. This value excludes the message length byte, the BASE_STATUS packet, the checksum and CRC bytes, and a presumed REG_REPLY packet. The BaseSlotSize indicates the number of bytes that are available for MAC and network ACKs, plus user data packets. This number does not include the
DNT500  2008 by RF Monolithics, Inc. 27 M-0500-0000 Rev D overhead required for headers of these packets, which must be factored into the slot size budget. To ensure that there is never a restriction on when registration or renewal may take place, space for a registration reply packet is always assumed. If this packet is not needed on a given hop, this space is unused. LeasePeriod This sets the duration for network address leases that remotes may receive from the base. If a period of zero is specified, then lease and network address functions are disabled. ARQ_Mode This sets the ARQ mode for delivery of application messages. In full ARQ mode, an ACK is expected from the receiving radio for each message addressed and sent to it. If no ACK is received, up to ARQ_AttemptLimit, efforts to send the data will be made, after which the message is discarded. In redundant transmit mode, each message is sent ex-actly ARQ_AttemptLimit times. No ACKS are sent or expected. This is primarily useful in cases where the number of attempts is 2 or 3, the data flow is time-critical, and the overhead of sending ACKs is not desired. ARQ_AttemptLimit This sets the maximum number of attempts that will be made to send a data packet on the RF link. Setting this parameter to the maximum value of 15 is a flag value indicating that there should be no limit to the number of attempts to send each packet (infinite number of attempts). This mode is intended for point-to-point networks in serial data cable replace-ment applications where absolutely no packets can be lost. TDMA_MaxNumSlots In TDMA access modes, this sets the number of slots that are allowed. In fixed slot mode, this allocates the number of slots directly. In dynamic slot mode, this sets the maximum number of slots that may be allocated according to the number of remotes that are registered. CSMA_Persistence In CSMA mode, this sets the 'persistence' parameter, or probability that a remote will transmit when it senses an open channel. Please refer to the section on Channel Access for more information. CSMA_MaxBackoff In CSMA mode, this sets the maximum length of time that a remote will back off for af-ter a failed transmit attempt. Please refer to the section on Channel Access for more in-formation. MaxPropDelay This is the maximum propagation delay that remotes and base will use in their slot timing calculations, in units of microseconds. This is used to pad the amount of time dedicated
DNT500  2008 by RF Monolithics, Inc. 28 M-0500-0000 Rev D to the signup slot. Increasing this value will subtract slightly from the overall slot time available to remotes for sending data. EpochMode This is a base-only parameter that governs how the base will select an epoch number at startup when it creates a network. In mode 0, the base will read the epoch number from NVRAM. In mode 1, it reads the value from NVRAM and increments it (and stores the result). In mode 2, it will generate a random epoch number at every startup. 4.2.3 Bank 2 - Status Registers (read only) Size in Bank Loc'n Name R/W bytes Range Default 02 00 MacAddress R 3 0..224 fixed value 02 03 CurrNwkAddress R 1 0..255 as set 02 04 CurrNwkID R 1 0..255 as set 02 05 CurrRF_DataRate R 1 0..4 as set 02 06 CurrFreqBand R 1 0..1 as set 02 07 LinkStatus R 1 0..1 current status 02 08 RemoteSlotSize R 1 0..255 current size 02 09 TDMA_NumSlots R 1 0..15 as set 02 0A TDMA_SlotStart R 1 0..255 current setting 02 0B TDMA_CurrSlot R 1 0..15 current slot 02 0C HardwareVersion R 1 0..255 0x00 = DNT500 rev A 02 0D FirmwareVersion R 1 0..255 current firmware load 02 0E FirmwareBuildNum R 2 0..216 current firmware load 02 0F Epoch R 1 0..255 as set 02 10 SuperframeCount R 1 0..255 current value 02 11 RSSI_Idle R 1 0..255 as set 02 12 RSSI_Last R 1 0..255 as set 02 14 CurrAttemptLimit R 1 0..255 as set 02 15 CurrRangeDelay R 1 0..255 as set MacAddress Returns the radio's unique 24-bit MAC address. CurrNwkAddress Returns the radio's current network address, if any. Some special values should be noted. The base always reports 0x00. If a remote does not have a network address, either be-cause lease mode is not enabled or it has not yet received one, it reports 0xFF. This re-turns the network ID of the network that the radio is currently assigned to or connected to. A value of 0xFF means the radio is in promiscuous mode and scanning for a network but has not yet joined one. CurrNwkID This returns the network ID of the network that the radio is currently assigned to or con-nected to. A value of 0xFF means the radio is in promiscuous mode and scanning for a network but has not yet joined one.
DNT500  2008 by RF Monolithics, Inc. 29 M-0500-0000 Rev D CurrRF_DataRate This returns the RF data rate of the network that the radio is currently assigned to or con-nected to. A value of 0xFF means the radio is scanning for a network but has not yet joined one. CurrFreqBand This returns the frequency band of the network that the radio is currently assigned to or connected to. A value of 0xFF means the radio is scanning for a network but has not yet joined one. LinkStatus This returns the radio's current connection status to the network. The following codes are defined: 0 = initializing 1 = unlinked, scanning for network 2 = linked RemoteSlotSize This returns the current remote slot size, defined as the maximum possible user data pay-load size in bytes. In TDMA modes where the slot size is automatically computed, this value is read-only. In manual TDMA mode and CSMA mode, this value must be set by the user. This value excludes the message length byte, REMT_STATUS packet, and checksum and CRC bytes. It indicates the number of bytes available for REMT_DATA and/or REMT_DATA_EXTs. It does not include the overhead bytes required for these packets, which must be figured into the slot size budget. TDMA_NumSlots In TDMA access modes, this returns the number of slots currently allocated. TDMA_CurrSlot This returns the current TDMA slot number. in modes where the slot position is auto-matically computed. In modes where this number is not applicable, the value is read as 0xFF. TDMA_SlotStart This returns the current TDMA slot position. In TDMA modes where the slot position is automatically computed, this value is read-only. HardwareVersion This returns an identifier indicating the type of radio. A value of 0x00 is defined for the DNT500 Rev A hardware. FirmwareVersion This returns the firmware version of the radio in 2-digit BCD format.
DNT500  2008 by RF Monolithics, Inc. 30 M-0500-0000 Rev D FirmwareBuildNum This returns the firmware build number, in binary format. Epoch Returns the current epoch number. SuperframeCount Returns the current superframe count. The superframe counter increments every 64 hops. RSSI_Idle Returns the last measurement of RSSI made during a time when the RF channel was idle. May be used to detect interferers. Read-only. RSSI_Last Returns the last measurement of RSSI made during receipt of an RF packet with valid CRC. Used for network commissioning and diagnostic purposes. CurrAttemptLimit This returns the value of ARQ_AttemptLimit currently in use (depending on the selected ARQ_Mode, it may not always match the local EEPROM value). CurrRangeDelay This returns the current propagation delay for this remote as measured from the base. 4.2.4 Bank 3 - Serial Size in Bank Loc'n Name R/W bytes Range Default 03 00 SerialRate R/W 2 0..216 115.2 kb/s (0x0004) 03 01 SerialParams R/W 1 0..7 8N1 03 03 SerialControls R/W 1 0..7 0X07 SerialRate This sets the serial rate divisor according to the following formula: Serial rate in b/s = 460800/SerialRate Serial rate division setting for commonly used baud rates are: Setting Serial rate 0x0000 460.8 kb/s 0x0001 460.8 kb/s 0x0002 230.4 kb/s 0x0004 115.2 kb/s (default) 0x0006 76.8 kb/s 0x0008 57.6 kb/s 0x000C 38.4 kb/s 0x0010 28.8 kb/s
DNT500  2008 by RF Monolithics, Inc. 31 M-0500-0000 Rev D 0x0018 19.2 kb/s 0x0030 9.6 kb/s 0x0060 4.8 kb/s 0x00C0 2.4 kb/s 0x0180 1.2 kb/s Note that if a value of 0x0000 is specified, the maximum data rate of 460.8 kb/s will be selected. SerialParams This sets the serial mode options for parity and stop bits: Setting Mode 0x00 No parity, 8 data bits, 1 stop bit 0x01 No parity, 8 data bits, 2 stop bits 0x02-03 Reserved 0x04 Even parity, 8 data bits, 1 stop bit 0x05 Even parity, 8 data bits, 2 stop bits 0x06 Odd parity, 8 data bits, 1 stop bit 0x07 Odd parity, 8 data bits, 2 stop bits Note that 8-bit data with no parity is capable of carrying 7-bit data with parity for com-patibility without loss of generality for legacy applications that may require it. SerialControls This register affects the way the radio responds to the various serial control lines. Ena-bling or disabling response to some serial control signals can facilitate communicating with devices that support only a reduced serial interface. The register is defined as a bit-mask, with the following options: bits 7..3 Reserved bit 2 Base DCD mode. 1 = The base will only assert DCD when at least one remote is registered (default). 0 = The base always asserts DCD, regardless of whether any remotes are attached. bit 1 RTS enable. 1 = Radio will respond to changes on the RTS control line (default). 0 = Radio ignores the RTS pin and assumes flow control is always asserted. bit 0 SLEEP enable. 1 = Radio will respond to changes on the SLEEP (DTR) control line (default) 0 = Radio ignores the SLEEP (DTR) pin and is always in the awake state. 4.2.5 Bank 4 - Host Protocol Settings Size in Bank Loc'n Name R/W bytes Range Default; Options 04 00 ProtocolMode R/W 1 0..1 0 = transparent; 1 = protocol 04 01 ProtocolOptions R/W 1 04 02 TxTimeout R/W 1 0..255 5 ms 04 03 MinPacketLength R/W 1 0..255 1 byte 04 04 StartupAnnEn R/W 1 0..1 0 = disabled; 1 = enabled
DNT500  2008 by RF Monolithics, Inc. 32 M-0500-0000 Rev D 04 05 TransLinkAnnEn R/W 1 0..1 0 = disabled; 1 = LINK announce 04 06 EscapeSequenceEn R/W 1 0..2 0 = enabled; 1 = startup, 2 = anytime 04 07 TransPtToPtMode R/W 1 0..1 0 = multipoint, 1 = point-to-point ProtocolMode Selects the host protocol mode. The default is 0, which is transparent mode, meaning the radio conveys whatever characters that are sent to it transparently, without requiring the host to understand or conform to the DNT500's built-in protocol. This setting is recom-mended for point-to-point applications for legacy applications such as wire replacements where another serial protocol may already exist. Setting this parameter to 1 enables the DNT500 host protocol, which is recommended for point-to-multipoint applications and is preferred for new designs. It is not necessary to define the same protocol mode for all ra-dios in a network. For example, it is frequently useful to configure all the remotes for transparent mode and the base for protocol mode. Note that it is possible for the host to switch the radio from transparent mode to protocol mode and back if desired by transmit-ting a special "escape sequence" code. See the section on the serial host protocol for more information. ProtocolOptions This is a bitmask that selects various options for the protocol mode. Default is 0x01. bit 7 Enable output of Instrumentation packets. bits 2..6 reserved bit 1 Enable LRC checksum byte in serial protocol. bit 0 Enable output of Announce packets. TxTimeout This sets the transmit timeout used for determining message boundaries in transparent data mode. Units are in milliseconds. The default is that a message boundary is deter-mined whenever there is more than a 5 ms gap detected between consecutive characters. MinPacketLength This sets the minimum message length used for determining packet boundaries in trans-parent data mode. The default is one byte. TransLinkAnnEn This enables a link announcement function for transparent mode. Whenever link is ac-quired or dropped, the strings "<LINK>" or "<DROP>" are sent to the host. EscapeSequenceEn Enables or disables the escape sequence which can be used to switch from transparent mode to protocol mode. Enabled by default. Valid settings are 0 = disabled, 1 = one chance at startup, 2 = enabled at any time. TransPtToPtMode This controls the behavior for addressing packets in transparent mode. When this setting is zero (default), in transparent mode the base will direct packets to the broadcast address. This is useful for point-to-multipoint where the base is sending data to multiple remotes,
DNT500  2008 by RF Monolithics, Inc. 33 M-0500-0000 Rev D for instance in applications where a wireless link is replacing an RS-485 serial bus. When this setting is one, in transparent mode the base will direct packets to the last remote that registered with it. This is useful for point-to-point networks where there are only two endpoints, for instance in applications where a simple serial cable is being replaced. 4.2.6 Bank 5 - I/O Peripheral Registers Size in Range Bank Loc'n Name R/W bytes in bits Default 05 00 GPIO0 R/W 1 1 0 05 01 GPIO1 R/W 1 1 0 05 02 GPIO2 R/W 1 1 0 05 03 GPIO3 R/W 1 1 0 05 04 GPIO2 R/W 1 1 0 05 05 GPIO3 R/W 1 1 0 05 06 ADC0 R 2 10 N/A 05 07 ADC1 R 2 10 N/A 05 08 ADC2 R 2 10 N/A 05 09 PWM0 R/W 2 9 0 05 0A PWM1 R/W 2 9 0 GPIO0..5 Writing to these registers sets the corresponding driver for pins that are enabled outputs. Writing to pins that are enabled as inputs enables or disables the internal pull-up. Reading these registers returns the current level detected on the corresponding pin. ADC0..2 Read-only, returns the current 10-bit ADC reading for the selected register. See the dis-cussion of the ADC_SampleIntvl parameter below. PWM0..1 Sets the PWM (DAC) outputs. The DC voltage derived from the integrated low-pass fil-ters on the PWM output provides and effective DAC resolution of 8 bits. The range of this parameter is 0x0000 to 0x0100. 4.2.7 Bank 6 - I/O setup Size in Range Bank Loc'n Name R/W bytes in bits Default; Options 06 00 GPIO_Dir R/W 1 4 0 (all inputs) 06 01 GPIO_Init R/W 1 4 0 (all zeros) 06 02 GPIO_Alt R/W 1 4 0x08 = use GPIO3 for RS485 enable 06 03 GPIO_MessageMode R/W 1 8 GPIO messages disabled 06 04 GPIO_SleepMode R/W 1 1 0 = off; 1 = use sleep I/O states 06 05 GPIO_SleepDDR R/W 1 6 0 (all inputs) 06 06 GPIO_SleepState R/W 1 6 0 (all zeros) 06 07 PWMA_Init R/W 2 10 0x0000 06 09 PWMB_Init R/W 2 10 0x0000 06 0B ADC_SampleIntvl R/W 2 16 0x0001 (10 ms) 06 0D ADC0 ThresholdLo R/W 2 10 0x0000
DNT500  2008 by RF Monolithics, Inc. 34 M-0500-0000 Rev D 06 0F ADC0_ThresholdHi R/W 2 10 0x03FF 06 11 ADC1_ThresholdLo R/W 2 10 0x0000 06 13 ADC1_ThresholdHi R/W 2 10 0x03FF 06 15 ADC2_ThresholdLo R/W 2 10 0x0000 06 17 ADC2_ThresholdHi R/W 2 10 0x03FF 06 19 IO_ReportEnable R/W 1 0..1 0 = off 06 1A IO_ReportInterval R/W 4 32 0x00007530 (every 30,000 hops) 06 1E IO_ReportAddress R/W 3 24 0x000000 GPIO_DIR This is a bitmask that sets whether the GPIOs are inputs (0) or outputs (1). The default is all inputs. GPIO_Init This is a bitmask that sets the initial value for any GPIOs which are enabled as outputs. For GPIOs enabled as inputs, this sets the initial pull-up setting. PWM0_Init This sets the initial value for PWM0 at startup. PWM1_Init This sets the initial value for PWM1 at startup. GPIO_Alt Provides and alternate function for GPIO3 as an RS-485 driver enable. GPIO_MessageMode This register enables a message to be sent to the base station whenever one of the GPIOs is triggered. If the radio is asleep, it will be awakened while the particular GPIO is as-serted. Bit Option 7-6 Message type for GPIO_3 5-4 Message type for GPIO_2 3-2 Message type for GPIO_1 1-0 Message type for GPIO_0 Message options: 0b00: Disabled Events are ignored and the radio is not awakened from sleep 0b01: Button Message An event message is sent reporting the state of the corresponding GPIO input. The state will be 0b0 since I/Os are triggered on logic low.
DNT500  2008 by RF Monolithics, Inc. 35 M-0500-0000 Rev D 0b10: Module I/O Message An event message is sent reporting the states of the entire I/O register bank 0b11: Registration Message A registration packet is sent to the base station. GPIO_SleepMode Enables setting of GPIOs to the designated direction and state whenever a device is asleep. GPIO_SleepDDR When GPIO_SleepMode is enabled, the three LSBs of this byte are used to set the direc-tion of the GPIOs during a device's sleep period. This enables the user to provide alter-nate configurations during sleep that will help minimize current consumption. Bits 0..2 correspond to GPIO0..GPIO2. GPIO_SleepState When GPIO_SleepMode is enabled, the three LSBs of this byte are used to set the output state of the GPIOs during a device's sleep period. This enables the user to provide alter-nate configurations during sleep that will help minimize current consumption. Bits 0..2 correspond to GPIO0..GPIO2. ADC_SampleIntvl The ADC_SampleIntvl sets the interval between the beginning of one ADC read cycle and the next ADC read cycle. The three ADC inputs are read on each ADC read cycle. An ADC_SampleIntvl count equals 10 ms. ADC0..2_ThresholdLo/Hi These values define thresholds to trigger an I/O report based on ADC measurements. If I/O reporting is enabled, single EVENT report containing the contents of the I/O bank is generated when a threshold is crossed. Reporting is "edge-triggered" with respect to threshold boundaries, not "level-triggered"; i.e., if the measurement remains there, addi-tional reports are not triggered until the value crosses the threshold again. The thresholds are met whenever one of the following inequalities are satisfied: ADCx < ADCx_ThresholdLo ADCx > ADCx_ThresholdHi IO_ReportEnable When enabled, this causes a remote to periodically send an EVENT message to its base containing the contents of the I/O bank. IO_ReportInterval When periodic I/O reporting is enabled, this sets the interval between reports. The default is once every 30000 hops (every 5 minutes, at the default 10 ms hop duration).
DNT500  2008 by RF Monolithics, Inc. 36 M-0500-0000 Rev D IO_ReportAddress Address to send I/O reports. Usually the base station address. 4.2.8 Bank FF - Special function This bank contains two user functions, UcReset and MemorySave. Bank Loc'n Name R/W bytes Range Description FF 00 UcReset W 1 0..90 00 = reset, 1 = clear status/address and reset, 0x5A = reset with factory defaults FF FF MemorySave W 1 0..1 0 = load factory defaults, 1 = save settings to EEPROM UcReset Writing a value of 0x00 to this location forces a software reset of the microcontroller. Writing a value of 0x01 resets the Link Status and erases any assigned Network Address before resetting. Writing a value of 0x5A forces a factory default before resetting. Writ-ing any other value returns an error. MemorySave Writing a zero to this location clears all registers back to factory defaults. Writing a one to this location commits the current register settings to EEPROM. When programming registers, all changes are considered temporary until this command is executed. 4.2.9 Protocol Mode Configuration/Sensor Message Examples For Example 5, the host configures the base station to transmit 24 dBm of RF power us-ing the SetRegister command, 0x04. The TxPower parameter is stored in bank 0x00, reg-ister 0x18. A one-byte parameter value of 0x03 selects the 24 dBm power level. The pro-tocol formatting for the command is: 0xFB 0x05 0x04 0x18 0x00 0x01 0x03 Note the order of the bytes in the command argument: register, bank, span, parameter value. When the base station receives the command it updates the parameter setting and return a SetRegisterReply message as follows: 0xFB 0x02 0x17 0x14 In order for this new RF power setting to persist through a base station power down, MemorySave must be invoked. This is done by setting a one-byte parameter in register 0xFF of bank 0xFF to 0x01 with another SetRegister command: 0xFB 0x05 0x04 0xFF 0xFF 0x01 0x01 The base station will write the current parameter values to EEPROM and return a SetReg-isterReply message: 0xFB 0x01 0x14
DNT500  2008 by RF Monolithics, Inc. 37 M-0500-0000 Rev D For Example 6, the base station host requests an ADC1 reading from a remote using the GetRemoteRegister command, 0x0A. The MAC address of the remote is 0x000102. The current ADC1 measurement is read from register 0x07 in bank 0x05. The ADC reading spans two bytes. The protocol formatting for this command is: 0xFB 0x07 0x0A 0x02 0x01 0x00 0x07 0x05 0x02 Note the remote MAC address 0x000102 is entered in Little-Endian byte order, 0x02 0x01 0x00. The ADC reading is returned in a GetRemoteRegisterReply message: 0xFB 0x0B 0x1A 0x00 0x02 0x01 0x00 0x80 0x07 0x05 0x02 0xFF 0x02 Substantial information is returned in the message. The last two byes of the message give the ADC reading in Little-Endian format, 0xFF 0x02. The ADC reading is thus 0x02FF. The RSSI value is the byte following the address, 0x80. The TxStatus byte to the right of the GetRemoteRegisterReply Packet Type is 0x00, showing the packet was acknowledged on the RF channel. 4.2.10 Protocol Mode Event Message Examples For Example 4, input GPIO2 (only) is configured to initiate an event message on remote 0x000102. This is done by configuring one-byte parameter GPIO_MessageMode with a SetRemoteRegister command. GPIO_MessageMode is register 0x03 of bank 0x06. Bits 4-5 control GPIO2 event messaging. Button Message mode is chosen, which sends the state of GPIO2, located in register 0x02 of bank 0x05, when a high-to-low transition oc-curs on GPIO2 (Button Message always reports a low state). The required GPIO_Mes-sageMode bit pattern is 00010000b or 0x10. The protocol formatting for this command is: 0xFB 0x08 0x0B 0x02 0x01 0x00 0x03 0x06 0x01 0x10 The GPIO_MessageMode parameter is updated and SetRemoteRegisterReply is returned: 0xFB 0x06 0x1B 0x00 0x02 0x01 0x00 0x8F The RSSI value is the byte following the address, 0x8F. The TxStatus byte to the right of the GetRemoteRegisterReply Packet Type is 0x00, showing the packet was acknowledged on the RF channel. In order for this new GPIO_MessageMode setting to persist through a base station power down, MemorySave must be invoked, as discussed in Example 5. When a high-to-low “button push” transition occurs on GPIO2, remote 0x001002 will send the following RxEvent message to the base station host: 0xFB 0x09 0x28 0x02 0x01 0x00 0x8E 0x02 0x05 0x01 0x00 The message is output as a PktType 0x28 RxEvent. Note that the RSSI value 0x8E is in-serted between the remote’s MAC address and the register address byte. Register 0x02 in bank 0x05 uniquely identifies GPIO2 as the source of the event message.
DNT500  2008 by RF Monolithics, Inc. 38 M-0500-0000 Rev D 5. DNT500 DEVELOPER’S KIT Figure 5.1 shows the main contents of a DNT500DK Developer’s kit: Figure 5.1 5.1 DNT500DK Kit Contents The kit contains the following items: • Two DNT500P Radios • Two DNT500 Interface Boards • Two 9 V Wall Plug Power Suppliers, 120/240 VAC • Two U.FL RF Jumper Cables • Two RJ-45 to DB-9F Cable Assemblies • Two A/B USB Cables • One RJ-11 to DB-9F Cable Assembly • Two 900 MHz Dipole Antennas • One DNT500 Documentation and Software CD 5.2 Additional Items Needed To operate the kit, the following additional items are needed: • Two PCs with Microsoft Windows® XP or Vista Operating System To fully test the kit’s functionality, the PCs should be equipped with high-speed serial ports capable of operation at 460.8 kb/s.
DNT500  2008 by RF Monolithics, Inc. 39 M-0500-0000 Rev D 5.3 Developer’s Kit Default Operating Configuration The default operating configuration of the DNT500DK developer’s kit is TDMA Mode 2, point-to-point, with transparent serial data at 115.2 kb/s, 8N1. One DNT500P is precon-figured as a base station and the other as a remote. The defaults can be overridden to test other operating configurations using the DNT500 Wizard utility discussed in Section 5.5. The default RF power setting is 10 dBm, which is suitable for side-by-side operation. The RF power level should be set higher as needed for longer range operation. Note that set-ting the RF power to a high level when doing side-by-side testing will overload the DNT500P receiver and cause erratic operation. 5.4 Development Kit Hardware Assembly Observe ESD precautions when handling the kit circuit boards. Referring to Figure 5.4.1, confirm each DNT500P is correctly plugged into an interface board, with the radio ori-ented so that its U.FL connector is next to the U.FL connector on the interface board. Check each radio’s alignment in the socket on the interface board. No pins should be hanging out over the ends of the connector. Next, install the U.FL jumper cables between the U.FL connectors on the radios and the interface boards. Then install the dipole anten-nas. As shown in Figure 5.4.2, confirm there is a jumper on pins J14. The interface boards can now be powered by the 9 V wall plug transformer power supplies (the inter-face boards can also be run for a short time from the 9 V batteries for range testing, etc.). Figure 5.4.1

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