Post by thread:Why, oh why...

...doesn't this work? Dear all Having served the first part of my pic apprenticeship (making leds flash, counting on 7 segment displays, etc), I've moved on to meatier things. My first stab was aimed at producing a measurement of a pulse length (yes, alright dammit, it's a R/C thing!). Despite extensive de-bugging, and appearing to work on MPSIM, the wretched thing keeps saying '00'. So, back to the drawing board, how about an interrupt driven program that just mirrors the input to an output pin? Here's my version (I'm sure it could be done in 4 1/2 bytes of program code, but it mirrors the way my other prog's supposed to work): list p=16f84 #include "c:\progra~1\mplab\p16f84.inc" left equ 0x0f right equ 0x10 _w equ 0x11 _status equ 0x12 ; You can assume WDT Off, PWRTE On, XT, 4Mhz Resonator org 0 goto main org 4 ; interrupt routine movwf _w ; save w movf status,w ; and status movwf _status bcf intcon,intf ; bsf status,rp0 btfss option_reg,intedg ; are we here for a rising or goto pulse_off ; falling edge pulse_on bcf option_reg,intedg ; next time, a falling edge bcf status,rp0 bsf porta,2 ; turn on a pin to match rb:0 goto int_exit pulse_off bsf option_reg,intedg ; next time, a rising edge bcf status,rp0 bcf porta,2 ; turn off to match rb:0 int_exit movf _status,w ; the usual gubbins movwf status swapf _w swapf _w,w ; retfie main clrf tmr0 bsf status,rp0 clrw movwf trisa ; make porta outputs (they are anyway?) movlw 1 movwf trisb ; make rb:0 an input movlw b'11000000' ; wait for rising edge on rb:0 movwf option_reg bcf status,rp0 movlw b'10010000' ; GIE and inte set movwf intcon clrw movwf left ; stuff left over from my digit movwf right ; displaying routines clrf porta clrf portb ; does clrfing portb cause a problem? loop goto loop ; hang about end Again, it works on the simulator, toggling RB:0, but in 'real life', all pins except RB:0 sit dormant. Can anyone suggest why? Regards John M