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Projects: RF communications - data transmitter
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RF communications - data transmitter

Introduction
This project demonstrates the 'AM RF Transmitter' sub-circuit and is intended to be used with project RFRX.QPR. Sending data over the RF link effects a simple remote control.

The target device is a PIC16F872. A smaller target such as the PIC16F84 could be used if required.

Operation
When the RS232 port receives a numeric character it is used as the remote receiver ID and initiates a data transmission. Data is transmitted to the remote receiver to turn a relay on and then off again (see project RFRX.QPR). Data is sent several times to ensure reliable data transfer. This is done since an acknowledgement is not possible with one-way communications.

The ID of the remote receiver may be anywhere within the range 0-255.

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'.


///////////////////////////////////////////////////////////////////////
////                           ARFTX.C                             ////
////                                                               ////
////  Demonstrates the 'AM RF Transmitter' (RFTX) sub-circuit      ////
////  based on the RF Solutions AM-RT4 transmitter module.         ////
////  The transmitter can address any receiver with an ID          ////
////  in the range 0-255 (see 'AM RF Receiver').                   ////
////  When a character in the range  '0' - '9' is received by      ////
////  the RS232 PORT it's used as the ID of the remote             ////
////  receiver. Data is sent to energise or de-energise a          ////
////  relay at the remote receiver.                                ////
////  See also project RFRX.QPR.                                   ////
////                                                               ////
////  This program is an example of how your application code is   ////
////  is organised. Note the #include "rftx.c", this include       ////
////  file was generated by QuickBuilder and contains all          ////
////  dirver code.                                                 ////
////                                                               ////
////  This demo is intended for a PIC16F872                        ////
////  Compile using CCS 'C'  visit www.quickbuilder.co.uk/qb/ccs   ////
///////////////////////////////////////////////////////////////////////
#include <16f872.H>

#fuses hs,nowdt,noprotect,put,nowrt,nolvp


#case

#define PORTA 5 
#define PORTB 6
#define PORTC 7
#define TRISA 0x85 
#define TRISB 0x86
#define TRISC 0x87

#include "rftx.c"




main() {
    char c,i;

    
    // initialise
    //------------
    setup_adc(ADC_OFF);
    setup_adc_ports(NO_ANALOGS);
    INIT_SUB_CIRCUITS();
        

    // main loop
    //----------
    while(1) {
        
        // wait for numeric character from console
        //
        c = RS232_IN();
        c = c-'0';      
        RFTX_REMOTE = c;            // set remote ID

        // send energise relay command 5 times
        //
        for (i=0 ; i<5; i++) {
            RFTX_START(0x0);        // data address
            RFTX_SENDDATA(1);       // energise relay
            RFTX_STOP();
        }
        
        // wait 2 secconds
        //
        delay_ms(2000);
        
        
        // send de-energise relay 5 times
        //
        for (i=0 ; i<5; i++) {
            RFTX_START(0x0);        // data address
            RFTX_SENDDATA(0);       // de-energise relay
            RFTX_STOP();
        }
    }

}
Copyright 2002-2009 Summit Electronics Ltd
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