40 KHz burst

[aherrera]

Thanks for your response, I did try, but something very odd happens, I changed it to an infinite loop to produce a frequency that I can measure:

Loop:
Toggle PulsePin
@NOP
@NOP
@NOP
@NOP
@NOP
@NOP
@NOP
@NOP
@NOP
@NOP
GOTO Loop

But for some reason, no matter how many @NOP I add, the frequency does not change and stays at 62.5 KHz

Any Ideas?

[Bruce]

This will get you spot-on 40kHz with a 4MHz oscillator.

  Cycles VAR BYTE 
  TRISIO.0=0  ' make pin an output first
  GOTO Main   ' jump over Pulse routine to Main

 ' @ 4MHz generate Cycles number of 40kHz pulses
asm
_Pulse
   bsf  GPIO,0 ; change to whatever port pin you have available
   goto $+1    ; 2uS per GOTO $+1
   goto $+1
   goto $+1
   goto $+1
   goto $+1     
   bcf  GPIO,0
   goto $+1 
   goto $+1
   goto $+1
   goto $+1
   goto $+1
   decfsz _Cycles,f
   goto _Pulse  ; 25uS total for 40kHz carrier
   RETLW 0      ; return to CALLing routine
ENDASM	  

Main:
  Cycles = 8    ' number of carrier cycles to generate
  CALL Pulse
  PAUSEUS 24
  GOTO Main
  END

Just enter the number of carrier cycles you need to generate in the Cycles var, and
CALL the routine.

[aherrera]

Thank you both a million for your help, I had done it with ASM and ENDASM but not as elegant as Bruce did, I just coded the delay using NOPs and the the eight pulses hard coded.