Hello,
I was building a small fan controller for my computer's case using PIC16F871, writing the code in ASM. I pieced together bits and pieces of code from the net, but suddenly it stopped working-- I must have made a change that killed it.
I backtracked all the way down to the bare minimum code, still unable to find the problem. I am sure it is a silly little mistake that I just cannot pick up. Any help is appreciated!
I am using LEDs to test it, outputting the three fan signals to PORTB0, 1 and 2. The interrupt should be occurring at 250 Hz, however, each LED is on for a few seconds, then the next LED turns on, and so on. This leads me to believe that the TMR1 was setup incorrectly. But I've double checked! I tried a different chip and even new XT OSC. No luck!
-Omar
I was building a small fan controller for my computer's case using PIC16F871, writing the code in ASM. I pieced together bits and pieces of code from the net, but suddenly it stopped working-- I must have made a change that killed it.
I backtracked all the way down to the bare minimum code, still unable to find the problem. I am sure it is a silly little mistake that I just cannot pick up. Any help is appreciated!
I am using LEDs to test it, outputting the three fan signals to PORTB0, 1 and 2. The interrupt should be occurring at 250 Hz, however, each LED is on for a few seconds, then the next LED turns on, and so on. This leads me to believe that the TMR1 was setup incorrectly. But I've double checked! I tried a different chip and even new XT OSC. No luck!
Code:
;16F871, 4mHz EXT OSC
list P=16F871
#include <p16F871.inc>
cblock 20h
pwmwar, dutycycle1, dutycycle2, dutycycle3
endc
org 0x0000
goto Init
ORG 0x0004
;Turn off interrupts
BCF INTCON, 7
BCF PIR1, 0
;If fan1 is less than the value of PWM Var, keep it on. Else, set it off.
BSF STATUS, C
MOVF dutycycle1, W
SUBWF pwmwar, W
BTFSS STATUS, C
BSF PORTB, 0
BTFSC STATUS, C
BCF PORTB, 0
;If fan2 is less than the value of PWM Var, keep it on. Else, set it off.
BSF STATUS, C
MOVF dutycycle2, W
SUBWF pwmwar, W
BTFSS STATUS, C
BSF PORTB, 1
BTFSC STATUS, C
BCF PORTB, 1
;If fan3 is less than the value of PWM Var, keep it on. Else, set it off
BSF STATUS, C
MOVF dutycycle3, W
SUBWF pwmwar, W
BTFSS STATUS, C
BSF PORTB, 2
BTFSC STATUS, C
BCF PORTB, 2
;Increase PWM Variable. If it has reached 100, reset it.
INCF pwmwar, F
MOVF pwmwar, W
SUBLW d'100'
BTFSC STATUS, Z
CLRF pwmwar
BSF INTCON, 7
retfie
Init
;Set TMR1 interrupt. Approximately 4000uS.
MOVLW 0x5F
MOVWF TMR1L
MOVLW 0xF0
MOVWF TMR1H
MOVLW 0x1
MOVWF T1CON
MOVLW 0xC0
MOVWF INTCON
bsf STATUS,RP0 ;bank 1
clrf TRISB ;Set PORTB as outputs
BSF PIE1, 0
bcf STATUS,RP0
;Set PWM Variable to 1
MOVLW 0x1
MOVWF pwmwar
start
;Setting dutycycles for each of the fans.
MOVLW d'99'
MOVWF dutycycle1
MOVLW d'1'
MOVWF dutycycle2
MOVLW d'50'
MOVWF dutycycle3
goto start
end-Omar