TRM-915-R250 RF Transceiver Module Data Guide
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5^ 58^ 58^ 59^ 59^ 60^ 61^ 62^ 62^ 64^ 64^ 64^ 66^ 68^ 70^ Configuration Registers Typical Applications Power Supply Requirements Antenna Considerations Helpful Application Notes from Linx Interference Considerations Microstrip Details Pad Layout Board Layout Guidelines Production Guidelines Hand Assembly Automated Assembly General Antenna Rules Common Antenna Styles Regulatory Considerations A large-print version of this document is available at www.linxtechnologies.com.
Ordering Information Electrical Specifications Ordering Information 250 Series Transceiver Specifications Product Part No. Description TRM-915-R250 Embedded Wireless Module, 250mW (900MHz) TRM-915-R250-CFT Embedded Wireless Module, 250mW (900MHz), Mexico Wi.232-FHSS-250-CFTC-R EVM-915-250-FCx Pinned, Pre-Certified Module, 250mW (900MHz) Wi.232FHSS-250-FCC-xx-R EVM-915-250-CFx Radiotronix Part No. Parameter Wi.232FHSS-250-R Power Supply Symbol Min. Typ. Max.
Pin Descriptions 250 Series Transceiver Specifications Parameter Symbol Min. Input Logic Low VI L Input Logic High VI H Output Logic Low VOL Typ. Max. Units 0 0.8 VDC 2.0 VCC VDC IOL = 8.5mA 0.6 VDC IOL = 10µA 0.1 VDC Notes Interface Section IOL = 25mA 1.0 Output Logic High VDC VOH IOH = -3mA VCC–0.7 IOH = -10µA VCC–0.1 IOH = -10mA VDC VCC-0.8 Pin Descriptions Pin Number Name I/O 1 PR_PKT O Processing Packet Indicator.
Theory of Operation Module Description The 250 Series transceiver is a low-cost, high-performance synthesized FSK transceiver. Its wideband operation gives it outstanding range while still meeting regulatory requirements. Figure 7 shows a block diagram for the module.
Module Operation The module employs a Frequency Hopping Spread Spectrum (FHSS) algorithm. It has 32 channels spaced on 750kHz boundaries with a guard band on either side. These channels are pseudo-randomly arranged into six unique hopping tables comprised of 26 channels. The order of these tables is chosen so that cross-correlation is minimized, allowing multiple networks to operate in proximity with minimal interference.
Low-Power States The module supports three power saving modes: Standby, Sleep and Deep Sleep. Standby and Sleep are included primarily for legacy compatibility with DTS and EUR Series modules. The hardware required to support these two low-power modes fully is not present in the 25 Series modules. As a result, the current consumption in these two modes is considerably higher than their DTS / EUR counterparts. It is recommended that applications utilize the Deep Sleep mode for power savings.
Reset to Factory Default It may be necessary to reset the non-volatile registers to their factory defaults. To reset the module, hold the CMD line low and cycle power to hardware-reset the module. The CMD line must remain low for a minimum of 600ms after resetting the module. Once the CMD line is released, the module’s non-volatile registers are reset to factory defaults. Exception Codes Exception codes are organized by type for ease of masking. Figure 9 lists the exception codes and their meanings.
Networking Modes The module has a very flexible addressing and networking scheme selected with the regNVNETWORKMODE and regNETWORKMODE registers. It can be changed during operation. The transmitting module addresses packets according to the network mode configuration. The receiving module processes all addressing types regardless of the network mode configuration. If the received message matches the addressing criteria, it is output on the UART. Otherwise it is discarded.
User Networking Mode User Networking Mode is a more complicated scheme than GUID mode. It uses the customer ID bytes (regCUSTID[0-1]) and two of the user destination bytes (regUSERDESTID[0-1]) as a destination address. The customer ID bytes are programmed at the factory and cannot be changed. The module’s local address is contained in two of the user source ID registers (regUSERSRCID[0-1]).
250 Series Transceiver User Network Mode Examples Destination Receiver Receiver Result of Result of ID from Dest Source Action Source User ID Received AND AND ID Mask Packet Mask Mask 1234 Any module with 123x FFF0 1230 1230 The results are equal, so the payload is output on the UART. Do not enable acknowledgements Figure 14: 250 Series Transceiver User Network Mode Examples Extended User Addressing Mode Extended User Networking Mode is the same as User Networking Mode but uses longer addresses.
Extended Preamble As the receivers scan the hop sequence channels they look for the preamble from a transmitter. When they detect this preamble, they stop scanning and wait for a packet header. From the packet header they are able to lock on to the transmitter and synchronize the timing. It is an advantage in some applications to keep the receivers asleep for long periods of time and wake them up only periodically to look for data.
Voltage Supply Rise Time Receive Signal Strength Indication (RSSI) The power supply rise time is extremely important. It must rise from ground to 2.7V in less than 1ms. If this specification cannot be met, an external reset supervisor circuit must be used to hold the module in reset until the power supply stabilizes. Failure to ensure adequate power supply rise time can result in loss of important module configuration information.
Hardware Reset (Input) During normal operation, the RESET line functions as an active-low hardware reset input. Taking this line low for at least 15μs forces the module’s controller into hardware reset. While the line is low, execution of module operations are suspended and all module lines revert to open-drain inputs with weak pull-ups. This behavior can be exploited during power-up if the VCC ramp time exceeds 1ms. By suspending execution, the dangers associated with slow VCC ramp are eliminated.
Using the Command Response (CMD_RSP) Line The CMD Line The CMD_RSP line is normally high, but the module lowers this line when responding to a UART command. This indicates to an external processor that the data on the TXD line is a response to a command and not data received over-the-air. The CMD line is used to inform the module where incoming UART data should be routed.
The UART Interface The module uses a standard UART interface for both data to be sent over the air and for configuring the module. The CMD line is used to tell the module if the data on the UART is for configuration or transmission. The lines follow the standard UART naming convention, so RXD is the data input into the module and TXD is the data output from the module. The UART interface expects 1 start bit, 8 data bits (LSB first), and 1 stop bit per byte with no parity (8-N-1).
Module Configuration The 250 Series module contains several registers that control its configuration and operation. The module’s default settings allow it to operate out of the box without any changes; however the registers allow the link to be customized to better suit the application if necessary. The register settings are stored in two types of memory inside the module. Volatile memory is quick to access, but it is lost when power is removed from the module.
250 Series Non-Volatile Read-Only Registers 250 Series Non-Volatile Read / Write Registers Continued Name Name Address Description Address Description Factory Default regMyGUID[3] 0x34 Factory programmed GUID used in GUID Networking Mode regNVUSERDESTID[0] 0x12 regMYGUID[2] 0x35 Factory programmed GUID used in GUID Networking Mode Destination Address for User and Extended User Networking Mode regNVUSERSRCID[3] 0x13 0xFF 0x36 Factory programmed GUID used in GUID Networking Mode Source
Writing to Registers Configuration Registers Writing to a volatile register is nearly instantaneous. Writing to a non-volatile register typically takes 16ms. Because the packet size can vary based on the need for encoding, there are two possible packet structures. The first structure writes a value that is less than 128 (0x80) and the second writes a value that is higher. The higher value must be split into two values. Figure 25 shows the byte sequences for writing a register in each case.
Power Mode - Address = 0x4D; NV Address = 0x02 The value in the regPWRMODE register sets the module’s output power. 250 Series RF Channels and Hop Sequences Channel Frequency Number (MHz) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 902.971 903.723 904.475 905.226 905.978 906.730 907.482 908.234 908.986 909.737 910.489 911.241 911.993 912.745 913.496 914.248 915.000 915.752 916.504 917.255 918.007 918.759 919.511 920.263 921.015 921.766 922.518 923.270 924.022 924.
UART Data Rate - Address = 0x4E; NV Address = 0x03 The value in regUARTDATARATE sets the data rate of the UART interface. Changing the non-volatile register changes the data rate on the following power-up or reset. Changing the volatile register changes the data rate immediately following the command acknowledgement. Figure 32 shows the command and response and Figure 33 shows the valid settings.
Transmit Wait Timeout - Address = 0x50; NV Address = 0x05 When a byte is received from the UART, the module starts a timer that counts down every millisecond. The timer is restarted when each byte is received. The value for the regTXTO register is the number of milliseconds to wait before transmitting the data in the UART receive buffer. The default setting for this register is 0x10 (~16ms delay).
CRC Control - Address = 0x53; NV Address = 0x08 The 250 Series protocol includes a Cyclic Redundancy Check on the received packets to make sure that there are no errors. Any packets with errors are discarded and not output on the UART. This feature can be disabled if it is desired to perform error checking outside the module. Set the regUSECRC register to 0x01 to enable CRC checking, or 0x00 to disable it. The default CRC mode setting is enabled.
Show Version - Address = 0x0A Setting this register to 0x00 suppresses the start-up message, including firmware version, which is sent to the UART when the module is reset. A value of 0x01 causes the message to be output after reset. By default, the module start-up message is output. Figure 43 shows examples of the commands and Figure 44 shows the available values.
Operating Mode - Address = 0x58; NV Address = 0x0D The value in the regOPMODE register sets the operating mode of the transceiver. If the module remains properly powered, and is awakened from a low power mode properly, the volatile registers retain their values when awakened. If the volatile registers become corrupted during low power, a software reset is forced and the module reboots. Awake mode is the normal operating mode.
User Destination ID These registers contain the address of the destination module when User Networking mode or Extended User Networking mode are enabled. User Networking mode uses bytes 0 and 1 to determine the destination address. Extended User Networking mode uses all four bytes. Please see the Networking Modes section for more details. Each register byte is read and written separately.
Exception Mask - Address = 0x6C; NV Address = 0x21 The module has a built-in exception engine that can notify the host processor of an unexpected event. When an exception occurs, this register is ANDed with the exception code. A non-zero result causes the EX line to be asserted. Reading the regEXCEPTION register clears the exception and resets the EX line. If the result is zero, the EX line is not asserted but the exception code is stored in the regEXCEPTION register.
Receiver LNA Mode - Address = 0x6F; NV Address = 0x24 By default, the module is factory-configured to use its internal Automatic Gain Control (AGC) circuit to manage receiver sensitivity. Reducing the gain increases the linearity of the receiver, but reduces maximum sensitivity; increasing the gain does the opposite.
As an example, if regAUTADD is set to 0x0F (Any Auto Address) and a GUID packet is received from another module, then regAUTADD reads back as 0x4F. The lower 4 bits indicate that the module is set to any auto address (0xF). The upper 4 bits indicate that the packet that was just received was a GUID Network Mode packet (0x4). My GUID These registers contain the factory-programmed read-only GUID address. This address is unique for each module and is used by all packet types as a unique origination address.
Exception - Address = 0x79 The module has a built-in exception engine that can notify the host processor of an unexpected event. If an exception occurs, the exception code is stored in this register. Reading from this register clears the exception and, if applicable, resets the EX line. If an exception occurs before the previous exception code is read, the previous value is overwritten. Figure 68 shows examples of the commands and Figure 69 shows the available values.
Typical Applications Antenna Considerations Figure 73 shows a circuit using the 250 Series transceiver. The choice of antennas is a critical and often overlooked design consideration. The range, performance and legality of an RF link are critically dependent upon the antenna. While adequate antenna performance can often be obtained by trial and error methods, antenna design Figure 75: Linx Antennas and matching is a complex task.
Interference Considerations Microstrip Details The RF spectrum is crowded and the potential for conflict with unwanted sources of RF is very real. While all RF products are at risk from interference, its effects can be minimized by better understanding its characteristics. A transmission line is a medium whereby RF energy is transferred from one place to another with minimal loss.
Pad Layout The pad layout diagram in Figure 79 is designed to facilitate both hand and automated assembly. 1.200” (30.48mm) 0.400” (10.16mm) 0.200” (5.08mm) 0.120” (3.04mm) Do not route PCB traces directly under the module. There should not be any copper or traces under the module on the same layer as the module, just bare PCB. The underside of the module has traces and vias that could short or couple to traces on the product’s circuit board. 0.400” (10.16mm) 0.150” (3.81mm) 0.130” (3.30mm) 0.100” (2.
The module is housed in a hybrid SMD package that supports hand and automated assembly techniques. Since the modules contain discrete components internally, the assembly procedures are critical to ensuring the reliable function of the modules. The following procedures should be reviewed with and practiced by all assembly personnel. Hand Assembly Pads located on the bottom Soldering Iron of the module are the primary Tip mounting surface (Figure 80).
General Antenna Rules The following general rules should help in maximizing antenna performance. 1. Proximity to objects such as a user’s hand, body or metal objects will cause an antenna to detune. For this reason, the antenna shaft and tip should be positioned as far away from such objects as possible. 2. Optimum performance is obtained from a ¼- or ½-wave straight whip mounted at a right angle to the ground plane (Figure 83).
Common Antenna Styles There are hundreds of antenna styles and variations that can be employed with Linx RF modules. Following is a brief discussion of the styles most commonly utilized. Additional antenna information can be found in Linx Application Notes AN-00100, AN-00140, AN-00500 and AN-00501. Linx antennas and connectors offer outstanding performance at a low price. Whip Style A whip style antenna (Figure 86) provides outstanding overall performance and stability.
Regulatory Considerations Note: Linx RF modules are designed as component devices that require external components to function. The purchaser understands that additional approvals may be required prior to the sale or operation of the device, and agrees to utilize the component in keeping with all laws governing its use in the country of operation.
Linx Technologies 159 Ort Lane Merlin, OR, US 97532 Phone: +1 541 471 6256 Fax: +1 541 471 6251 www.linxtechnologies.com Disclaimer Linx Technologies is continually striving to improve the quality and function of its products. For this reason, we reserve the right to make changes to our products without notice. The information contained in this Data Guide is believed to be accurate as of the time of publication. Specifications are based on representative lot samples.
