Related Manuals for RFM DNT500 Series
Summary of Contents for RFM DNT500 Series
- Page 1 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...
- Page 2 (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.
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Page 3: Table Of Contents
TABLE OF CONTENTS INTRODUCTION........................ 1 Why Spread Spectrum?....................1 Frequency Hopping versus Direct Sequence ..............2 DNT500 RADIO OPERATION ..................4 Network Synchronization and Registration ..............4 Transparent and Protocol Serial Port Modes..............4 RF Data Communications ....................5 RF Transmission Error Control..................5 Network Configurations.................... - Page 4 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.............
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Page 5: Introduction
DNT500 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. -
Page 6: Frequency Hopping Versus Direct Sequence
DNT500 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. - Page 7 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...
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Page 8: Dnt500 Radio Operation
DNT500 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. -
Page 9: Rf Data Communications
DNT500 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. -
Page 10: Network Configurations
DNT500 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. -
Page 11: Point-To-Multipoint Network Operation
DNT500 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. -
Page 12: Csma Modes
DNT500 Access Mode Description Max # of Remotes Remote Slot Size CSMA polling 1024 manual CSMA contention 1024 manual 2 (default) TDMA dynamic slots up to 15 automatic TDMA fixed slots up to 15 automatic 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. -
Page 13: Tdma Modes
DNT500 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. -
Page 14: Network Configuration Planning
DNT500 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. - Page 15 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.
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Page 16: Serial Port Operation
DNT500 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. -
Page 17: Sleep Mode
DNT500 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. -
Page 18: Dnt500 Hardware
DNT500 3. DNT500 HARDWARE 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. -
Page 19: Specifications
DNT500 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 FCC 15.247 FHSS 38.4, 115.2 and 200 kb/s, up to 28 dBm FCC 15.247 Digital Modulation (DSS) 500 kb/s, up to 19 dBm Number of Hopping Patterns Hop Dwell Time... -
Page 20: Module Interface
DNT500 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: Name Description Reserved pad. Leave unconnected. RSVD Reserved pad. -
Page 21: Input Voltages
DNT500 Name Description Reserved pad. Leave unconnected. RSVD Reserved pad. Leave unconnected. RSVD Reserved pad. Leave unconnected. RSVD Default functionality is UART flow control input for the module’s host. A logic low allows data /UART0_RTS flow from the module to the host; a logic high blocks data flow from the module to the host. UART received data output to host from module. -
Page 22: Interfacing To 5 V Logic Systems
DNT500 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. -
Page 23: Connecting Antennas
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. -
Page 24: Protocol Messages
DNT500 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: 3 … Length PktType variable number of arguments … LRC* The scale above is in bytes. - Page 25 DNT500 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.
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Page 26: Escape Sequence
DNT500 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. -
Page 27: Cfg Select Pin
DNT500 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. -
Page 28: Bank 0 - Transceiver Setup
DNT500 4.2.1 Bank 0 - Transceiver Setup Size in Bank Loc'n Name R/W bytes Range Default, Options DeviceMode 0..2 0 = Remote, 1= Base, 2 = PTT Remote RF_DataRate 0..4 0 = 500, 1 = 200, 2 = 115.2, 3 = 38.4 kb/s, 0xFF = auto HopDuration 4..4000 10 ms (0x00C8) - Page 29 DNT500 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.
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Page 30: Bank 1 - System Settings
DNT500 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”. - Page 31 DNT500 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.
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Page 32: Bank 2 - Status Registers (Read Only)
DNT500 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. - Page 33 DNT500 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.
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Page 34: Bank 3 - Serial
DNT500 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. -
Page 35: Bank 4 - Host Protocol Settings
DNT500 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... - Page 36 DNT500 TransLinkAnnEn 0..1 0 = disabled; 1 = LINK announce EscapeSequenceEn 0..2 0 = enabled; 1 = startup, 2 = anytime TransPtToPtMode 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.
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Page 37: Bank 5 - I/O Peripheral Registers
DNT500 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. - Page 38 DNT500 ADC0_ThresholdHi R/W 0x03FF ADC1_ThresholdLo R/W 0x0000 ADC1_ThresholdHi R/W 0x03FF ADC2_ThresholdLo R/W 0x0000 ADC2_ThresholdHi R/W 0x03FF IO_ReportEnable 0..1 0 = off IO_ReportInterval 0x00007530 (every 30,000 hops) IO_ReportAddress 0x000000 GPIO_DIR This is a bitmask that sets whether the GPIOs are inputs (0) or outputs (1). The default is all inputs.
- Page 39 DNT500 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.
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Page 40: Bank Ff - Special Function
DNT500 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 UcReset 0..90 00 = reset, 1 = clear status/address and reset, 0x5A = reset with factory defaults MemorySave 0..1... -
Page 41: Protocol Mode Event Message Examples
DNT500 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. -
Page 42: Dnt500 Developer's Kit
DNT500 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 •... -
Page 43: Developer's Kit Default Operating Configuration
DNT500 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.
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