Texas Instruments TRF4903 User manual

User's GuideSWRU010A – October 2004 – Revised May 2005
TRF4903 With MSP430 Demonstration and Development
Evaluation Kit
This document presents the contents of the TRF4903 demonstration and developmenttool kit. The user manual provides information on how to operate theMSP-TRF4903-DEMO kit and describes its hardware and software. Users shouldunderstand the MSP430F449, TRF6903, and the TRF4903 to obtain the full benefit ofthis user manual.
Different topics covered in this manual may require different levels of expertise. Thefirst two chapters are focused on how the kit operates.
If you want to build your own prototype, review the third chapter on how to loadfirmware. The later chapters cover hardware and software topics that may require someadditional expertise.
Other related Texas Instruments information includes the following that may be helpful:
TRF4903 data sheet SWRS023TRF6903 data sheet SWRS022MSP430F449 data sheet SLAS344TRF6903 Design Guide SWRU009TRF6901 FAQ SLAD008For design and product information related to the TRF6903, MSP430, and similar products,go to:
http://www.ti.com/ismrf
http://www.msp430.com
PDF documents and zip files may be located on Texas Instruments’ website by typing in theliterature number in the Search text box; for example, typing in SWRS022 will locate theTRF6903 data sheet.
Contents1 TRF4903 Demonstration and Evaluation Kit Overview ................................................................. 22 Demonstrating a Wireless Link............................................................................................. 23 Prototyping .................................................................................................................... 74 PCB Hardware Overview ................................................................................................... 95 Software Overview ......................................................................................................... 146 SCHEMATICS .............................................................................................................. 22
List of Figures
1 Top-Side, Back-Side of the TRF4903 Demonstration Board .......................................................... 42 JTAG Connector ............................................................................................................. 83 TRF4903 RF Block Diagram ............................................................................................... 9
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1 TRF4903 Demonstration and Evaluation Kit Overview
1.1 Description
1.2 Contents
1.3 Equipment Requirement
2 Demonstrating a Wireless Link
TRF4903 Demonstration and Evaluation Kit Overview
4 Block Diagram of the MSP430F44x ..................................................................................... 105 Top-Side Silk Screen ...................................................................................................... 106 Bottom-Side Silk Screen .................................................................................................. 117 JP1 Pin-Out Configuration ................................................................................................ 138 Game Application FLow Chart – Transmit Mode ...................................................................... 159 Game Application FLow Chart – Receive Mode ....................................................................... 1610 Communication Protocol .................................................................................................. 1711 TRF4903 Graphical User Interface for RF Evaluation ................................................................. 2112 Schematic (Page 1) ........................................................................................................ 2213 Schematic (Page 2) ........................................................................................................ 2314 Schematic (Page 3) ........................................................................................................ 24
List of Tables
1 4-Bit DIP Switch (SW1) Settings and Transmit Frequencies .......................................................... 52 Bill of Materials ............................................................................................................. 113 Antenna Suppliers .......................................................................................................... 134 6-Byte Transmission Data Packet ........................................................................................ 185 TRF4903 Game Application Register Values .......................................................................... 18
This chapter provides an overview of the TRF4903 demonstration and development kit.
The MSP-TRF4903-DEMO kit is used to demonstrate a unidirectional radio frequency (RF) data linkwithout the need of an external computer, and for prototyping by downloading new software code to theMSP430F449 through the JTAG connector. This kit is used to evaluate the Texas Instruments TRF4903, asingle-chip multiband RF transmitter. The schematics and layout of the board can be used as a referencedesign if desired, limited by the software system parameters of the demonstration firmware.
The TRF4903 demonstration and development kit contains:•One TRF4903 demonstration board (transmitter)•One TRF6903 demonstration board (receiver)•User’s manual (this document)
Software is not included in the kit. Software and hardware documentation related to this kit can bedownloaded at http://www.ti.com/ismrf.
The following equipment is not included in this kit and is required to operate the MSP-TRF4903-DEMO kit:•Four AAA batteries•MSP430 bus expansion cable for the JTAG connector, required only for prototyping purposes.
This chapter explains how to operate the MSP-TRF4903-DEMO kit to demonstrate a RF bidirectional link.
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2.1 Board Description
Demonstrating a Wireless Link
The demo kit has two circuit boards. The first circuit board (unit) is the transmitter and consists of aTRF4903 RF transmitter and a MSP430F449 microcontroller. The second circuit board in the kit is areceiver and consists of a TRF6903 RF transceiver and a MSP430F449 microcontroller. The TRF6903board is capable of sending and receiving half-duplex wireless data on the European and NorthAmerican/US ISM bands. However, for demo purposes, the TRF6903 board is used as a receiver for theTRF4903 transmitter.
The microcontroller firmware is configured by default to use the 902-MHz to 928-MHz ISM frequencyband. Additional firmware has been developed to operate the TRF4903 demo kit in the European868-MHz ISM band.See the Operating the TRF4903 Demo Kit in the 868-MHz EU ISM Band applicationnote (SWRA047) for further information. The firmware for the 868-MHz EU band can be downloaded fromthe http://www.ti.com/ismrf website. Figure 1 shows top-side and back-side views of the transmit TRF4903circuit board.
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l m n
a b c-1 c-2 d
e
f
k j i h g
Demonstrating a Wireless Link
Figure 1. Top-Side, Back-Side of the TRF4903 Demonstration Board
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2.2 Operation
Demonstrating a Wireless LinkCircuit board features:
a On/Off switchb Battery holder for two AAA batteries in series (batteries not included).c-1, c-2 Headers used to access the MSP430F449 I/O ports.d TRF4903 RF transmittere Antenna jumper (0- Ωresistor) used to select either the SMA connector or PCBantenna (selecting both not recommended).f On-board PCB antenna (default configuration). The antenna has modest gain andradiates in the direction of the bend in the long arm.g SMA connector footprint for an external antenna or test equipment (SMA connectornot included).h Four-bit DIP switch used in the link demonstration mode to change the trans-mit/receive frequencies. The switch is connected to MSP430 I/O ports P3.0, P3.1,P3.2, and P3.3.i Four buttons used for the demonstration game application, connected to MSP430I/O ports P1.0 through P1.3.j RS-232C connectork JTAG connectorl TRF4903 I/O header used to monitor or control the TRF4903.m Zero- Ωresistor R42, remove to disable the MSP430F449 (or short reset to groundat JTAG connector).n MSP430F449 microcontroller
A simple game is implemented in the firmware to demonstrate unidirectional RF communication betweenthe TRF4903 transmit board and the TRF6903 configured in the receive mode. The user starts the gameby pushing any sequence of four colored buttons. The corresponding colored LED’s light up on the receiveboard in the same sequence.•Successful packet reception: The LED’s light up in same sequence as the transmit button sequence.•Communication error: NO LED’s illuminate on the receiving board if there was a communication error.
2.2.1 Preparing for Operation
Before operating the units as a demonstration, make sure that you have done the following:•Slide the on/off switch to ON•Place two AAA batteries on each demonstration board•Have the same 4-bit DIP switch (SW1) configuration on both boards
Table 1 shows the transmit and receive frequencies selected with the 4-bit DIP switch (SW1). Both circuitboards must have the same channel switch settings in order for the demonstration game to operatecorrectly.
Table 1. 4-Bit DIP Switch (SW1) Settings and Transmit Frequencies
1234 SW1 Setting TX Frequency (MHz) RX Frequency (MHz)(1=On, 0=Off) 4903 TX Board 6903 RX Board
0000 902.3988 891.6992
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Demonstrating a Wireless Link
Table 1. 4-Bit DIP Switch (SW1) Settings and Transmit Frequencies(continued)
1234 SW1 Setting TX Frequency (MHz) RX Frequency (MHz)(1=On, 0=Off) 4903 TX Board 6903 RX Board
0001 903.218 892.51840010 904.4468 893.74720011 905.266 894.56640100 906.0852 895.38560101 907.7236 897.0240110 909.362 898.66240111 910.1812 899.48161000 911.8196 901.121001 912.6388 901.93921010 913.458 902.75841011 914.2772 903.57761100 915.506 904.80641101 916.3252 905.62561110 917.554 906.85441111 918.3732 907.6736
2.2.2 Power Up
Slide the power switch to ON. The STANDBY, MODE, and LOCK DETECT LED’s blink to indicate powerup condition. After the power-up initialization, the TRF4903 based transmit unit goes into Standby Mode(IDLE_STATE) and Mode 0 and waits for a button press. This turns off all the LED’s.
Note:
The LOCK LED on the transmit board is connected to the multiplexed pin 16 of theTRF4903. Initially, the TRF4903 is programmed to obtain a lock detect signal on themultiplexed pin 16. This turns on the LOCK DETECT LED on the transmit board.
Once the TRF4903 is ready to transmit data, the multiplexed pin 16 isprogrammed for the DCLK mode and the recovered data clock at 38.4 kbps isoutput at terminal 16. This blinks the LOCK LED at 38.4 kbps. Once thetransmission is complete, the TRF4903 goes back to Standby (IDLE_STATE)and the LOCK LED is turned off again.
The TRF6903 based receive board goes into the receive mode to monitor for any transmit activity. TheRSSI indicator LED is lighted to indicate the signal strength in the frequency channel of operation. Redindicates the lowest signal strength and green indicates the highest.
2.2.3 Wireless Demonstration
Only the TRF4903 transmit board is configured to initiate wireless communication. Assume that Board A isthe transmit board and transmits the first four-button transmitted sequence and Board B receives thetransmission.
Use Board A to start the wireless demonstration by pressing the four colored buttons in any sequence withabout 1/2 second between successive buttons. Once the four buttons are pushed, Board A initiates thetransmission.
Once the transmission is received by Board B and if the response sequence matches, the LEDs areturned on in the same sequence as the buttons were pushed at the transmitter side.
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3 Prototyping
3.1 Connecting to the MSP430 JTAG
Prototyping
If there are errors due to poor or lost transmission, NO LED lights up on the Board B. This concludes thebasic demonstration of the one-way RF communication.
On completion, the transmit board waits for another button press and the receive board goes back toreceive mode to listen for a new button sequence.
2.2.4 RSSI Indicator
Since the TRF4903 is a transmitter, it does not have an RSSI feature. The TRF6903 receive board isequipped with a receive signal strength indicator (RSSI) that illustrates the signal strength on the receiver.Four levels are used to indicate signal strength. Red is the lowest and means no signal was received,while green indicates the highest level of signal strength. The RSSI shows transmission activity when theother board is transmitting a data stream on the same DIP switch configuration or when there is anotherexternal RF source broadcasting at that channel frequency. For the best results, the two boards should bein the same plane of orientation, with the bend in the long antenna arm pointed towards each other.
2.2.5 Error Conditions
Cycle the system power to reinitialize the hardware if you get error conditions that persist. Error conditionsare defined as lost communication, mismatch in response sequences, or response time outs. In somecases, antenna orientation, signal multipath, or another interfering signal can increase errors.
This chapter explains how to operate the MSP-TRF4903-DEMO kit to prototype new applications.
The MSP-TRF4903-DEMO is designed for rapid application development. The MSP430 MCU flashmemory can repeatedly be erased and reprogrammed. The on-chip emulation logic allows real-timedebugging and fast code development. The MSP-TRF4903-DEMO and the MSP430 flash emulation toolprovide everything that is required to develop an entire firmware project.
For information go to http://www.msp430.com
Connector J2 provides access to the JTAG port of the MSP430 microcontroller on theMSP-TRF4903-DEMO circuit board. The MSP-FET430 flash emulation tool (FET) interface boardMSP-FETP430IF (not included in this kit) connects to J2 and allows real-time in-system emulation.Programming the MSP430, assembler/C source-level debugging, single stepping, multiple hardwarebreakpoints, full-speed operation, and peripheral access are fully supported in-system using the JTAGconnector. Figure 2 shows the connections of the MSP-TRF4903-DEMO to the JTAG cable provided bythe MSP430 FET interface board.
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Keyed
Connector
Red Stripe
3.2 Loading the MSP430 With the FIrmware
Prototyping
Figure 2. JTAG Connector
The MSP-TRF4903-DEMO comes with source code installed on the MSP430 to run the demo program.The user can develop new application software that can be downloaded to the MSP430 MCU through theJTAG connector. Since the Compiled C code size is greater than 4 kB, only unrestricted versions of theIAR development environment (not the Kickstart version) must be used for downloading and modifying thecode.
The workspace file for compiling the demo source code is TRF4903_Demo_US.eww, developed with IARcompiler version 3.20a.
The following steps show how to open the project file and program the MSP430.
Step 1. Insert the two AAA batteries and slide the on/off switch to ON.Step 2. Start the Workbench (START->PROGRAMS->IAR SYSTEMS->IAR EMBEDDEDWORKBENCH
Step 3. Use FILE->OPEN WORKSPACE to open the workspace file at: <Installation root>\ …\TRF4903_Demo_US.eww
Step 4. Use PROJECT->BUILD ALL to compile and link the source code. You can view thesource code by double-clicking Common Sources, and then double-clicking on thesource files in the workspace windowStep 5. Ensure that the C-SPY Debugger is properly configured for the Parallel Port used.(Choose PROJECT->OPTIONS->FET DEBUGGER and select ->LPT1 (default) or LPT2or LPT3 for the Parralel Port Configuration).Step 6. Use PROJECT->DEBUG to start C-SPY. C-SPY erases the device Flash and downloadsthe application object fileStep 7. In C-SPY, use DEBUG->GO to start the applicationStep 8. In C-SPY, use DEBUG->STOP DEBUGGING to exit C-SPYStep 9. In Workbench, use FILE->EXIT to exit Workbench
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4 PCB Hardware Overview
4.1 Hardware Overview
4.2 TRF4903 RF Block Diagram
PA_OUT
Serial
Interface
CLOCK
DATA
STROBE
PA
Band-gap
/N Prescaler
/A-
Counter
Loop Filter
Brownout MODE
/Div. CTRL 8
6
Output
Divider PFD
CPs /Ref
/B-
Counter
Lock
Detector
VCO
24
23
22
3
2
1
4
32/33
19 20
XTAL_SW
XTAL
14 CP_OUT12VCO_TUNE
2...255
1, 2, 3
Detect
Bit Synchronizer
Data Clock
TX_DATA
and
STDBY
MUX
DET_LD_DCLK
16
XTAL
Switch
PCB Hardware Overview
The MSP430 is now programmed with the game demonstration code and ready to operate.
This chapter provides the default PCB hardware documentation in detail and provides alternateconfigurations that the user may want to implement.
The TRF4903 ISM-band transmitter IC operates from 315 MHz to 950 MHz. It has low power consumptionand an operating voltage of 2.2 V to 3.6 V. It features an integer-N PLL synthesizer and supports FSK andOOK operation. Other features include on-chip clock recovery, brownout detector, and XTAL frequencytrimming in software. See the TRF4903 data sheet (SWRS023 ) for detailed information on the TRF4903features.
The TRF4903 demonstration and development kit (MSP-TRF4903-DEMO) provide a stand-alonedemonstration of a unidirectional link using the MSP430F449, the TRF4903 RF transmitter and theTRF6903 RF transceiver configured as a receiver.
Figure 3 shows the block diagram of the TRF4903 ISM transceiver IC.
Figure 3. TRF4903 RF Block Diagram
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4.3 MSP430F449 Block Diagram
4.4 Demo Board Schematics
4.5 Top and Bottom Silk Screen and Drawing
PCB Hardware Overview
Figure 4 shows the block diagram of the MSP430F449 microcontroller IC.
Figure 4. Block Diagram of the MSP430F44x
See SWRR009 for the TRF4903 transmit side schematics and SWRR001 for the TRF6903 receiver sideschematics. All the schematics for the demonstration boards can be found at http://www.ti.com/ismrf .
Figure 5 and Figure 6 show the top-side and bottom-side TRF4903 circuit board silkscreen.
Figure 5. Top-Side Silk Screen
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4.6 Parts List
PCB Hardware Overview
Figure 6. Bottom-Side Silk Screen
Table 2. Bill of MaterialsQTY VALUE MFG MFG NO. DESCRIPTION REFERENCE
1 0.5 pF AVX 06035A0R5CAT2A CAP, CER, 0603, 50 V, ±0.25 pF, 0.5 pF C24
1 1.5 pF AVX 06035A0R5CAT2A CAP, CER, 0603, 50 V, ±0.25 pF, 1.5 pF C64
1 22 pF AVX 06035A220FAT2A CAP, CER, 0603, 50 V, 1%, 22 pF C18
1 27 pF AVX 06035A270FAT2A CAP, CER, 0603, 50 V, 1%, 27 pF C17
2 33 pF AVX 06035A330FAT2A CAP, CER, 0603, 50 V, 1%, 33 pF C15, C48
1 43 pF AVX 06035A430FAT2A CAP, CER, 0603, 50 V, 1%, 43 pF C14
1 100 pF AVX 06035A101FAT2A CAP, CER, 0603, 50 V, 1%, 100 pF C54
1 120 pF AVX 06035A121FAT2A CAP, CER, 0603, 50 V, 1%, 120 pF C21
1 75 pF AVX 06035A820JAT2A CAP, CER, 0603, 50 V, 5%, 75 pF C20
1 5600 pF AVX 06035A562JAT2A CAP, CER, 0603, 50 V, 5%, 5600 pF C22
19 0.1 µF AVX 0603YC104KAT2A CAP, CER, 0603, 16 V, 10%, 0.1 µF C23, C30, C31,C33, C34, C37,C40, C43, C44,C45, C46, C51,C52, C53, C55,C56, C57, C58, C59
4 1 µF AVX TAJA105K016R CAP, TANT, 3216, 16 V, 10%, 1 µF C26, C27, C28, C29
4 22 µF CAL CHIP GMC32Y5V226Z16NT CAP, CER, 1210, 16 V, -20 +80%, 22 µF C32, C42, C47, C60
3 RED KingBrite W934-IT DIODE, LED, T1, RED, 12.5 MCD at 20 mA D10, D11, D12
2 MBRM120LT Motorola MBRM120LT1 or 3 DIODE, SCHOTTKY, 20PIV, 1A, DO-216AA D9, D13
3 FMMT2222A Central Semi CMPT2222A XSTR, NPN, GenPurp, 75hfe, 40 Vceo, 600 mA, Q1, Q2, Q3SOT23
1 15 nH Murata LQW1608A15ND00 IND, SMD, 0603, ±0.5 nH, 650 mA, 15 nH L6
1 270 nH Murata LQW1608A270ND00 IND, SMD, 0603, ±0.5 nH, 650 mA, 270 nH L5
8 0 ΩAVX CJ10-000-T RES, 0603, 5%, 0 ΩJP1, R6, R29, R31,R41, R42, R56
6 10 ΩRES, 0603, 5%, 10 ΩR35, R38, R39,R40, R43, R44
6 100 ΩRES, 0603, 5%, 100 ΩR45, R46, R47,R48, R50, R58
3 200 ΩRES, 0603, 5%, 200 ΩR61, R62, R63
1 1 k ΩRES, 0603, 5%, 1 k ΩR11
1 7.5 k ΩRES, 0603, 5%, 7.5 k ΩR9
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4.7 Alternate Hardware Configurations
PCB Hardware Overview
Table 2. Bill of Materials (continued)QTY VALUE MFG MFG NO. DESCRIPTION REFERENCE
13 10 k ΩRES, 0603, 5%, 10 k ΩR13, R14, R15,R16, R17, R18,R19, R20, R53,R57, R64, R65, R66
1 15 k ΩRES, 0603, 5%, 15 k ΩR10
1 82 k ΩRES, 0603, 5%, 82 k ΩR30
1 Header 7 x 2 SAMTEC TSW-107-07-T-D CONN, HDR, P, 14, 7 x 2 x 0.1, TTH J2mm
1 Header 7 x 2 x SAMTEC TMM-107-01-T-D-SM CONN, HDR, P, 14, 7 x 2 x 2 mm, SMT J52 mm
1 Header 3 MOLEX 22-28-4030 CONN, HDR, P, 3, 3 x 1x 0.1, TTH JP2
1 CONN DB-9 AMP 745781-4 CONN, PCB, DB9, F, RT J1
1 SMA EDGE Johnson 142-0701-801 (-801 = Au CONN, Coax, SMA, Edge, SMT, 0.062 Thk PCB CO1Components Plate)
1 4 x SPST CTS 219-4MST SW, Slide, 4 X SPST, 20 V at 100 mA, SMT, Sealed SW1
4 PB SPST, NO OMRON B3W-4050 SW, PB-SPST, NO, 50 mA, 24 V, TTH SW2, SW3, SW4,SW5
1 SS12SDP2 NKK SS12SDP2 SW, SLIDE SPDT, PCB, 30 V at 0.2 A SW6
1 12 mm Switch OMRON B32-1320 Cap, SW, 12 mm sq, fits B3W-4050, Orange See sampleCap
1 12 mm Switch OMRON B32-1330 Cap, SW, 12 mm sq, fits B3W-4050, Yellow See sampleCap
1 12 mm Switch OMRON B32-1350 Cap, SW, 12 mm sq, fits B3W-4050, Green See sampleCap
1 12 mm Switch OMRON B32-1380 Cap, SW, 12 mm sq, fits B3W-4050, Red See sampleCap
1 2468 MemProtectionD BC2AAAPC Battery holder, 2 X AAA, PCB Mount BAT1ev
1 TP Red Kobiconn 41-77B4 Test Point, RED, 0.037 TTH TP2
3 TP Green Kobiconn 42-23F8 Test Point, GRN, 0.037 TTH TP1, TP3,TP 5
1 TP White Kobiconn 33-85B4 Test Point, WHT, 0.037 TTH TP4
1 TRF4903PW Texas Instru- TRF4903PW IC, RF XMIT, 315-930 MHZ, FQFP48 U1ments
1 MSP430F449 Texas Instru- MSP430F449IPZ IC, MicroP, MixSig, 16-Bit RISC, 32 kb Flash, U6ments FQFP100
0 TPS76330DB Texas Instru- TPS76330DBVT IC, PS LDO Regulator, 30 V at 150 mA, SOT32-5 U3V ments
1 MAX3232- Texas Instru- MAX3232CD IC, RS232 Driver, 2 Driver, 2 Receiver, SOIC16 U4SOIC16 ments
1 19.6608 MHz CRYSTEK Corp 017119 XTAL, SMT, 19.6608 MHz, LCC-5X7 Y2
1 32.768 kHz Seiko 628-SPT1A-0368 XTAL, SMT, 32.768 kHz, CM202 Y4
The MSP-TRF4903-DEMO kit is preconfigured to function under the following assumptions:•North American ISM frequency band, 902-928 MHz•NRZ (non-return to zero) coding•FSK (frequency shift keying)•38.4 Kbps•On-board PCB antenna
The kit can be reconfigured to a limited extent. These options are covered in this section.
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1
2 3
PCB Hardware Overview
4.7.1 European ISM Frequency Band
The European 868-MHz to 870-MHz ISM band is not covered in the preconfigured system, but it can bemodified by changing software variables; download new software configurations through the JTAGconnector. No hardware changes are needed, but the antenna matching is not optimized for this band.See the Operating the TRF4903 Demo Kit in the 868-MHz EU ISM Band application note (SWRA047) forfurther information. The firmware for the 868-MHz EU band can be downloaded from thehttp://www.ti.com/ismrf website.
4.7.2 External Antenna
Significant range performance may be achieved when an external antenna is used. The actualperformance improvement will depend on the antenna design and proper impedance matching. A solderpad for a SMA connector is provided on the circuit board. The antenna can be mounted onto the SMAconnector. Jumper (JP1) setting must be moved to connect the external antenna to the rest of the RF frontend. Shorting pins 2 and 3 of JP1 with a 0- Ωresistor connects the circuit board antenna. To connect anexternal antenna, open pins 2 and 3 and short pins 1 and 2 with a 0- Ωresistor. Figure 7 shows the pin-outconfiguration at the silk screen. Table 3 lists information for some antenna suppliers. If the PCB antenna isnot used, leave it unconnected, remove the matching components from each end, and substitute one100- Ωresistor at each end; this will prevent unwanted coupling between the PCB antenna and the RFsignal.
Figure 7. JP1 Pin-Out Configuration
Table 3. Antenna Suppliers
Supplier Web Site Part Number ISM Band
Nearson www.nearson.com S467AM-915S USS467AH-868S EuropeanMaxRad www.maxrad.com MEXR902SM USMobilemark www.mobilemark.com PSWN3-925S USPSTNS-900S EuropeanW. Badland Ltd. www.badland.co.uk Various models US/ EuropeanRadiall/Larsen www.radialllarsen.com Various models USSPDA24832 European
4.7.3 RS-232C Port
The circuit board is designed for communication to the MSP430 microcontroller through the RS232 serialport. The UART driver is implemented in firmware and is used in the RF evaluation mode.
4.7.4 On-Board LDO Voltage Regulator
In normal operation, the battery is connected directly to the circuit board power through R31. There is afootprint for a low dropout (LDO) regulator for cases where a higher-voltage power supply is used insteadof the on-board batteries. To add an LDO regulator, remove R31 and install Texas Instruments regulatorTPS76330DBV at the U3 footprint.
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5 Software Overview
5.1 Software Description
Software Overview
4.7.5 High-Frequency Crystal
The board has a footprint for a high-frequency (4 MHz) microprocessor crystal (Y3) as well as thelow-frequency crystal. The factory board configuration uses the 32-kHz watch crystal (Y4). An internalfrequency multiplier generates the 2.4576-MHz system clock.
4.7.6 Discrete LC Filter or SAW Filter
A SAW filter is typically used to band-limit the received RF signal and reduce RF interference outside theISM band. The SAW filter from Murata (SAFC915MA70N-TC11) gives a pass band typical of 902 MHz to928 MHz, while providing about 30-dB attenuation in the stop band. Insertion loss in the pass band isabout 4.5 dB. This causes a corresponding loss in operational range due to signal attenuation. The SAWfilter is not normally installed at the factory in order to maximize range rather than noise immunity.
There are other hardware configurations for attenuating transmitter harmonics and filtering out-of-bandreceived noise. It is recommended that discrete LC filters be used for this purpose. See the TRF6903Design Guide (SWRU009 ) for a detailed discussion on the design of discrete LC filters.
4.7.7 Disabling the MSP430
In normal operation, the MSP430 microprocessor controls the TRF4903 transmitter and the game userinterface. The RF section can also be controlled directly with external computer software. To disable themicrocontroller, either short the MSP430 reset pin (RST) to ground at the JTAG connector (preferredmethod), or remove R42, which disables the voltage supply to the MSP430. The TRF4903 can then becontrolled directly through J5, the 14-pin surface-mount header.
4.7.8 Game and RF Operational Modes (Jumper JP2)
The TRF4903 circuit board comes with jumper JP2 set in the position for the game (demonstration link)mode, where two circuit boards communicate with each other in game mode to demonstrate a wirelesslink. In the other jumper position (RF evaluation mode), the TRF4903 is controlled from external softwarerun on a PC and the commands are passed through the MSP430. This software can be downloaded fromthe http://www.ti.com/ismrf website.
This chapter describes the link demonstration firmware that has been flashed to the microcontroller andexternal control software for RF test and evaluation.
The demonstration software implements a simple one-way game application utilizing a half-duplexunidirectional wireless link. The transmit board and receive board have different software. The 4903-basedtransmit side software routines are discussed in this section. The software was developed using IAR’sEmbedded Workbench, version 3.20a (www.iar.com). The software files are:•trf4903_demo_us.ewp – Project file•trf4903_main.c – Main body of the program written in C languge. All subroutines are called from thisprogram
•rf_reg.c – C file to configure the TRF4903 registers•api_4903.c – C file for UART interface•trf4903.s43 – Assembly subroutine to program the TRF4903 registers•radio49.s43 – Assembly subroutines that execute wireless transmission commands•setdco.s43 – Assembly routine that sets the baseband clock.
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5.2 Flowchart
Initialize
IDLE_STATE
Local_Button_Active
Transmit_Packet
Local Button Activated
All 4 Button pushed or 3 sec Timeout
Power Up
Software Overview
After power up initialization, the controller is configured as a state machine to run the link demonstration.Figure 8 illustrates the state machine flowchart for the TRF4903 transmit board and the TRF6903 receiveboard. Buttons and timer functions are handled through interrupt subroutines.
Figure 8. Game Application FLow Chart – Transmit Mode
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Initalize
Receive_Normal
Local_Button_Active
Transmit_Packet
Wait_For_Local_
Button_Response
LED_Remote_Que
Receiver_Wating_For
_Response
LED_Response
_Result
Done
Turn on LED
Power Up
Received Remote Button Packet
Local Button Activated
Received Response Packet | 5 Second Timed Out
All 4 Button Pushed | 3 sec. Timeout
All Response Button | 3 sec. Timeout Local Button Initiated COM
Response to Remote Button Complete
Software Overview
Figure 9. Game Application FLow Chart – Receive Mode
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5.3 Wireless Protocol
.... .... 0
Pre-Amble
101 111
Packet Start Bit
Word0 Synch Bit Word1 Synch Bit
Word0 Word1
Communication Protocol
0
Bit Width = 26 S
....
Software Overview
The wireless data communication protocol is digital FSK at 38,400 bits per second with NRZ coding. Thecommunication protocol used for the demonstration board includes preamble, packet start bit, andword-sync bit as illustrated in Figure 10 .
Figure 10. Communication Protocol
Preamble
The function of the preamble is to train the receive hardware to set the proper reference voltage thresholdto extract 1 and 0 data. The preamble consists of a train of alternating ones and zeros. A longer preamblemay give better performance at a cost of more time to deliver an equivalent data packet. The currentdesign has a preamble 100 bits long, or 2.6 ms in duration. Shorter lengths may be used for moretime-critical applications.
5.3.1 Packet Start and Word-Sync Bits
The packet start bit and the word sync bit are used by the receive routine to adjust microprocessor timingfor sampling the incoming data stream. The packet start bit occurs once at the beginning of the datapacket to indicate the end of the preamble and the start of data. The sync bit is used to resynchronize thebit stream and the data sampling timer. Over time the receive timing could shift in phase relative totransmit timing due to the small variation in component tolerances and performance. This shows up as anerror in sampled data. The problem gets worse as the packet size increases. Resynchronization minimizesthis drift over time.
Although resynchronization can be done at byte boundaries, word boundary resynchronization is slightlymore efficient.
The data clock recovery feature of the TRF4903 and the TRF6903 provides a convenient way tosynchronize data.
5.3.2 Wireless Data Stream
The wireless data stream for the game application is implemented as follows:•User initiates an RF transmission on Board A (TRF4903 demo board) by pushing four buttons in anysequence.
•User sequence is sent to Board B (TRF6903 demo board) using the transmission data packetdescribed in Table 4 , embedded in the communication protocol described in Figure 10 . Thetransmission packet includes a unique header, four bytes with the button IDs and a checksum.•Board A then goes to the IDLE_STATE and waits for further button pushes.•Board B receives the 6 data bytes, calculates the checksum and compares it with the receivedchecksum. If checksums match, it lights up the LED’s on the receive board in the same order in whichthe transmit buttons were pressed. The Board B then goes into the receive mode and listens fortransmissions.
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5.4 TRF4903 Registers
5.5 Transmit-Side Wireless Subroutines
Software Overview
Table 4. 6-Byte Transmission Data Packet
Header Byte Button 1 Button 2 Button 3 Button 4 Checksum Byte
OxFa ID Byte ID Byte ID BYte ID BYTe
5.3.3 Checksum Byte
Each packet has a checksum byte at the end of the data packet (see Table 4 ). The checksum byte iscalculated by summing the first 5 bytes of the packet and ignoring overflow.
The TRF4903 has five control registers (A through E) that are initialized using an on-chip serial portinterface (SPI). Table 5 shows the values loaded into the registers by the microprocessor during demoprogram initialization.
Table 5. TRF4903 Game Application Register Values
Register Parameter Value
A PA attenuation 0 dBMode 0 TXCharge Pump 0.5 mAFrequency Band 915 MHzTX Frequency 902.3488 MHzB PA attenuation 0 dBPA EnabledMode 1 TXModulation FSKBrownout threshold 2.2 VBrownout detector OnTX Frequency 902.3488 MHzC Reference divider 48Reference frequency 409.6 kHzD Crystal Tune 20.23 pFReset Signal for PFD Derived From PrescalerCrystal Switch during OOK OpenE Transmit Capture Mode (TXM) HighDividers D1 D2 D3 38.4 kbpsTerminal 16 Multiplex function Lock Detect
The game application uses a combination of C and MSP430 assembly language functions to implementdifferent communication tasks that are required to receive and send data. Brief descriptions of thesesubroutines follow.
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Software Overview
5.5.1 program_TRF4903_word()
This function configures one of the five registers of the TRF4903 transceiver. Here is a sample code onhow to use this function so that you can program all five registers:struct REGA_BITS{
unsigned long BND:2; //1-0 Band of operationunsigned long CP_Acc:2; //3-2 speed up time for the CPunsigned long reserved0:1unsigned long TX:1; //5unsigned long PA0:2; //7-6unsigned long B_DIV_M0:9; //16-8 Mode 0 = Transmitunsigned long A_DIV_M0:5; //21-17unsigned long ADDR:2; //23-22};
union TRF_REGA{
unsigned long all;struct REGA_BITS bit;};
struct TRF_REG{
union TRF_REGA a;union TRF_REGB b;union TRF_REGC c;union TRF_REGD d;union TRF_REGE e;};
void configure_trf4903(void)
{
int pointer;
P4OUT&=0xfe;
pointer=(int)f_sel; trf4903.a.bit.B_DIV_M0=MAIN_B_T[pointer];
trf4903.a.bit.A_DIV_M0=MAIN_A_T[pointer];
program_TRF4903_word(trf4903.a.all);
trf4903.b.bit.B_DIV_M1=MAIN_B_R[pointer];
trf4903.b.bit.A_DIV_M1=MAIN_A_R[pointer];
program_TRF4903_word(trf4903.b.all);
program_TRF4903_word(trf4903.c.all);
trf4903.d.bit.XTAL_Tune = XTAL_OFFSET;program_TRF4903_word(trf4903.d.all);
program_TRF4903_word(trf4903.e.all);
5.5.2 send_RF(unsigned int, unsigned int*)
This function is used to transmit a packet of wireless data stream. Here is an example of how it is used:union RF_XMIT_PACKET{
unsigned int w[MAXWORD];unsigned char b[MAXBYTE];}xmit;
void SendRFWithModeSelect(unsigned int ByteCnt){
switch(trf4903.e.bit.TXM){
case 0:send_RF(ByteCnt,xmit.w);
break;
case 1:trf4903.e.bit.MUX = 1; //set to DCLK modeprogram_TRF4903_word(trf4903.e.all);
send_RF_DCLK(ByteCnt,xmit.w);
break;
}
}
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5.6 External Control Software for RF Evaluation Mode
Software Overview
In the RF evaluation mode, the TRF4903 transmitter is controlled by external software run on a PC ratherthan by the game/demo firmware installed on the MSP430. There is no operational link in RF evaluationmode; the transmitter is set to one operational state at a time. Jumper JP2 sets the board operation modeto game/demo or RF evaluation.
The RF control software has a graphical user interface (GUI) for the user to set the transmitter frequency,power, etc. In the RF evaluation mode, the external software GUI controls the TRF4903 by passing controlregister words through the computer COM1 serial port, RS232 driver IC (MAX3232), and finally throughthe MSP430 microcontroller to the transmitter.
Figure 11 shows the graphical user interface that communicates with the circuit board through the COM1RS232 serial port. The user must click on the adjacent COM1 button if its caption reads Com1 Closed inorder to open the serial port. The RF evaluation GUI is written in Borland C++ Builder, version 6, andintegrates utilities from Winsoft Ltd. to write to the serial port (Comport). In RF evaluation mode, the serialport COM1 is used to control the TRF4903.
An example GUI setup for the TRF4903 (transmit mode) is shown in Figure 11 . Several boxes and picklists have to be filled out by the user before clicking the Send All button to configure the RF transceiver.Some of the boxes will toggle state when the cursor is placed over the box contents and double-clicked(power amplifier).
The crystal frequency should be set to 19.6608 MHz. Set the reference divider to 48 (enter value and clickthe Set button). The crystal tune capacitance should be set to an intermediate value like 17, 20, or 22 pF.The charge pump current is 0.5 mA. In the Mode Select box, Either A-Word or B Word can be selected fortransmit mode. The phase-frequency detector reset should be set to Prescaler. Enter the power ampoutput frequency and click the Set Freq button; the software rounds off the output frequency to an integermultiple of the reference frequency. The Band Select List box can be used to select for the ISM band ofoperation. The Modulation box should be set to FSK. For initial evaluation, set TXM=0 and TXDATA toLow. The Multiplex Terminal List box can be used to define the output at terminal 16 of the TRF4903.
Other communication utilities such as HyperTerminal or ProComm can be used in place of the externalsoftware GUI to control the TRF4903 in pass-through mode. Set the transmission raw data rate to38.4 kbps, 8 bits data, no parity, 1 stop bit, no flow control or handshake. Send the 24-bit control words forregisters A through E in ASCII hex with a leading asterisk (hex 2A) and trailing carriage return (hex 0D),i.e., “*[A][B][C][D][E]<CR>”.
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