Generic RF Receiver

[dhouston]

This receives 12-48 bits of PDM (Pulse Distance Modulation) or PWM (Pulse Width Modulation) codes with bit periods from 1.7-2.5mS and with start pulses of 1.9-9.6mS.

To use with IR, change all While GPIO.1 to While !GPIO.1 and vice versa.

It uses Timer1 to measure start pulses and bit periods and Timer0 to timeout if a bit period exceeds 2.5mS.

'=======================| RF RECEIVER |=========================

'PIC12F629 @ 4MHz          455 words		uses MPASM

'Pin 1 - Vdd
'Pin 2 - GPIO.5
'Pin 3 - GPIO.4
'Pin 4 - GPIO.3
'Pin 5 - GPIO.2 RS232 output @ 9600bps
'Pin 6 - GPIO.1 Receives up to 48 bits of PDM/PWM RF with lead-in of 2-9mS
'Pin 7 - GPIO.0
'Pin 8 - Vss
'===============================================================

@ __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF 

DEFINE OSCCAL_1K 1 
DEFINE OSC 4					
DEFINE DEBUG_REG GPIO
DEFINE DEBUG_BIT 2 				
DEFINE DEBUG_MODE 1 				
DEFINE DEBUG_BAUD 9600
	
@Timer1 = TMR1L
Timer1  VAR  	WORD EXT
T0IF   	VAR 	INTCON.2               	'TMR0 overflow flag 
TMR1ON 	VAR	T1CON.0  		'Timer1 ON/OFF control bit
RF      VAR 	byte[6]
ID	VAR	byte
period	VAR 	word
i       VAR 	byte   
bits	VAR	byte
bytes	VAR	byte           	
sof  	VAR 	word 				
cnt	VAR	byte
	       
        CMCON     	=%00000111      'disable comparators        
        INTCON		=%00000000	'disable interrupts
        T1CON		=%00000000	'TMR1 no prescaler	
        OPTION_REG	=%10000001	'TMR0 1:4 prescaler, no PU	
                
        DEBUG "RF Receiver",13,10
        
init:	RF[0]=0:RF[1]=0:RF[2]=0:RF[3]=0:RF[4]=0:RF[5]=0
        While !GPIO.1:Wend		'wait rising edge	
        TMR1ON=0:Timer1=0:TMR1ON=1	'stop, clear, start TMR1	
        While GPIO.1:Wend               'wait falling edge
        TMR1ON=0:sof=Timer1		'stop, read TMR1
        If (sof<1900) Then init
        If (sof>9600) Then init
        While !GPIO.1:Wend		'wait rising edge
        TMR1ON=0:Timer1=0:TMR1ON=1	'stop, clear, start TMR1
        TMR0=49:T0IF=0:cnt=0		'reset TMR0, cnt	        	
        i=0
        Repeat
          While GPIO.1                  'wait falling edge
	    If T0IF Then 
              GoSub cycles 			          
            EndIf  
          Wend				'falling edge
          While !GPIO.1                 'wait rising edge
	    If T0IF Then
              GoSub cycles
            EndIf  
          Wend				'rising edge
          TMR1ON=0:period=Timer1        'stop, read TMR1
	  Timer1=0:TMR1ON=1 		'clear, start TMR1           
          TMR0=49:T0IF=0:cnt=0		'reset TMR0, cnt
          If (period<850) Then init		
          If (period>1300) Then			
            RF.0(i)=1				
          EndIf
          i=i+1
        Until (i>47)
break:  If (i<12) Then init
        bytes=i/8
        If i//8 Then
	  bytes=bytes+1
        EndIf
        Debug ihex2 i        
        For i = 0 to bytes-1
  	  Debug ihex2 RF[i]
        Next    
        DEBUG 32,dec sof,13,10
        GoTo init

cycles: TMR0=49:T0IF=0:cnt=cnt+1
	If (cnt>2) Then break          'timeout @2.5mS
	Return
		
        End