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Projects: RF communications - slave transponder
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RF communications - slave transponder

Introduction
This project demonstrates the 'AM RF Transponder' sub-circuit when used as a slave. The slave transponder operates by receiving data sent over a radio frequency link from a remote 'AM RF Transponder' operating as a master. When data is received the appropriate request is carried out and the slave transponder replies to the originating master. See also project RFXM.QPR.

Operation
When RFX_NOTIFY indicates the arrival of new data, the request contained in the data is carried out. In this case when RFX_RDATA[0] is a '1' the temperature on the 'DS1820 Temperature sensor' is read and sent back to the requesting transponder.

Note: The ID of the remote transponder is automatically saved to RFX_REMOTE when the master transponder sends the request.

The ID of this (slave) transponder is set by 'PORT4BIT', which has four external connections. The ID may be anywhere within the range 0-15.

Application code
Below is the application code for this project. To use it, select and copy (ctr-insert) the code below, paste it into a text editor and save it as a 'C' file in your working directory.

You may also need to change the build output path using 'Project | Options'.



///////////////////////////////////////////////////////////////////////
////                         ARFXS.C                               ////
////                                                               ////
////  This project demonstrates the 'AM RF Transponder'            ////
////  sub-circuit used as a slave. When RF data is sent to the     ////
////  transponder it responds by measuring the temperature         ////
////  using the 'DS1820 Temperature sensor' and transmits the      ////
////  result to the transponder that originated the request.       ////
////  Connect PORT4BIT-0,1,2,3 to GND to give the transponder      ////
////  an identification of 0. More transponders can be used if     ////
////  required.                                                    ////
////  See also project RFXM.QPR.                                   ////
////                                                               ////
////  This program is an example of how your application code is   ////
////  is organised. Note the #include "rfxs.c", this include       ////
////  file was generated by QuickBuilder and contains all          ////
////  dirver code.                                                 ////
////                                                               ////
////  Compile using CCS 'C'  visit www.quickbuilder.co.uk/qb/ccs   ////
///////////////////////////////////////////////////////////////////////
#include <16f84.H>

#fuses   XT,NOPROTECT,NOWDT

#case

#define PORTA 5 
#define PORTB 6
#define TRISA 0x85 
#define TRISB 0x86

#include "rfxs.c"


main() {
    signed long l;


    // initialise
    //------------    
    INIT_SUB_CIRCUITS();
    RFX_LOCAL = PORT4BIT_READ();    // set local ID
    RFX_RON();                      // receiver on

    

    // main loop
    //----------
    while(1) {
        
        if ( RFX_RINCOMING() )
            RFX_RDO();                  // poll transponder
    
        if (RFX_RNOTIFY) {
                       
            if ( RFX_RDATA[0] == 1 ) {  // if reading requested then
                BUSYLED_SET(1);         // led on
                l = DS1820_1READ_TEMPERATURE(); // read temperature
                RFX_TSTART(0x0);        // data address
                RFX_TSENDDATA(l);       // data lo byte
                RFX_TSENDDATA(l>>8);    // data hi byte
                RFX_TSTOP();            // end transmission
                BUSYLED_SET(0);         // led off
            }
            
            RFX_RNOTIFY = 0;
        }
    }
}

Copyright 2002-2009 Summit Electronics Ltd
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