Help with code in Assembly ! Something is Wrong

[financecatalyst]

Someone helped me with this interrupt part of the code in assembly when I was creating a dimmer progam for my fan. Unfortunately I cannot get hold of that person & I don't have any knowledge of assembly, so if someone can help me correct the problem...

This is the only part of the code in assembly, rest is in PBP & I am comfortable dealing with it. Now, this following code controls the speed of a fan based on a variable DimmerVal which is a byte. In my code when I assign DimmerVal=0, fan stops & DimmerVal=255 takes it to full speed. The problem is that the fan speed sometimes variates & automatically goes back to the assigned speed after some moments, looks like some kind of synchronisation error with zero-detector input, but I am not sure because I can't understand this code. can someone help please....

ISR:
asm
        movwf   wsave           
        swapf   STATUS, W
        clrf    STATUS          
        movwf   ssave           
        movf    FSR,w
        movf    fsave           
        movf    PCLATH, W       
        movwf   psave


        ; get ready to jump within the ISR page
        movlw   ((INTHAND) >> 8) 
        movwf   PCLATH
        btfsc   INTCON, INTF
        goto    ZeroCrossingInt
        btfss   INTCON, T0IF    
        goto    EndInt
T0Overflow
        bcf     INTCON, T0IF
        bsf     _oDimmer        
        goto    EndInt

ZeroCrossingInt
        bcf     INTCON, INTF   
        movf    _DimmerVal,w
        movwf   TMR0           
        bcf     _oDimmer        

EndInt  ; restore the machine state and return from interrupts
        movf    fsave,w
        movwf   FSR             ; restore FSR
        movf    psave,w
        movwf   PCLATH          ; restore PCH
        swapf   ssave,w
        movwf   STATUS          ; restore Status
        swapf   wsave,f
        swapf   wsave,w         ; restore WREG
        retfie
endasm

[Kamikaze47]

If it helps, I have commented the ASM code with the equivalent PBP commands. Its hard to say what the problem is without the rest of the program.

ISR:
asm
        movwf   wsave             ; Save the machine state for restore at end of interrupt routine
        swapf   STATUS, W
        clrf    STATUS          
        movwf   ssave           
        movf    FSR,w
        movf    fsave           
        movf    PCLATH, W       
        movwf   psave


        ; get ready to jump within the ISR page
        movlw   ((INTHAND) >> 8)                ; PCLATH=INTHAND>>8
        movwf   PCLATH                           
        btfsc   INTCON, INTF                    ; If INTF=1 THEN GOTO ZeroCrossingInt
        goto    ZeroCrossingInt                      
        btfss   INTCON, T0IF                    ; If T0IF=0 THEN GOTO EndInt
        goto    EndInt
T0Overflow                                      ; T0Overflow:
        bcf     INTCON, T0IF                    ; T0IF=0
        bsf     _oDimmer                        ; oDimmer=1
        goto    EndInt                          ; GOTO EndInt

ZeroCrossingInt                                 ; ZeroCrossingInt:
        bcf     INTCON, INTF                    ; INTF=0 
        movf    _DimmerVal,w                    ; TMR0=DimmerVal
        movwf   TMR0                             
        bcf     _oDimmer                        ; oDimmer=0

EndInt  ; restore the machine state and return from interrupts
        movf    fsave,w
        movwf   FSR             ; restore FSR
        movf    psave,w
        movwf   PCLATH          ; restore PCH
        swapf   ssave,w
        movwf   STATUS          ; restore Status
        swapf   wsave,f
        swapf   wsave,w         ; restore WREG
        retfie
endasm

[Kamikaze47]

This may be more helpful to you. This is the same thing, but done using DT's instant interrupts. You also need to INCLUDE the DT_INTS and ReEnterPBP files relevant to your PIC.

ASM
INT_LIST macro ;    IntSource, Label,       Type, ResetFlag?
        INT_Handler TMR0_INT,  tmr0_handler, PBP,  yes
        INT_Handler INT_INT,   int_handler,  PBP,  yes
    endm
    INT_CREATE 
ENDASM

@ INT_ENABLE TMR0_INT
@ INT_ENABLE INT_INT

main:
' your main program
goto main

tmr0_handler:
oDimmer=1
@ INT_RETURN

int_handler:
TMR0=DimmerVal
oDimmer=0
@ INT_RETURN

[financecatalyst]

This may be more helpful to you. This is the same thing, but done using DT's instant interrupts. You also need to INCLUDE the DT_INTS and ReEnterPBP files relevant to your PIC.

ASM
INT_LIST macro ;    IntSource, Label,       Type, ResetFlag?
        INT_Handler TMR0_INT,  tmr0_handler, PBP,  yes
        INT_Handler INT_INT,   int_handler,  PBP,  yes
    endm
    INT_CREATE 
ENDASM

@ INT_ENABLE TMR0_INT
@ INT_ENABLE INT_INT

main:
' your main program
goto main

tmr0_handler:
oDimmer=1
@ INT_RETURN

int_handler:
TMR0=DimmerVal
oDimmer=0
@ INT_RETURN

I am still trying to understand the above code -
Is this code running timer0 interrupt all the time?
I learnt that in DIMMERS, you have to control the +ve half of the cycle only, so timer0 should be loaded after checking the positive half making the PIC pin HIGH and keeping the triac ON for that period.

ALSO FOR THE ASM PART:

        btfsc   INTCON, INTF                    ; If INTF=1 THEN GOTO ZeroCrossingInt (1)
        goto    ZeroCrossingInt                 ;        (2)
        btfss   INTCON, T0IF                    ; If T0IF=0 THEN GOTO EndInt                (3)
        goto    EndInt                              ;                                                           (4)
T0Overflow                                      ; T0Overflow: (5)
        bcf     INTCON, T0IF                    ; T0IF=0  (6)
        bsf     _oDimmer                        ; oDimmer=1 (7)
        goto    EndInt                          ; GOTO EndInt (8)

ZeroCrossingInt                                 ; ZeroCrossingInt: (9)
        bcf     INTCON, INTF                    ; INTF=0 (10)
        movf    _DimmerVal,w                    ; TMR0=DimmerVal(11)
        movwf   TMR0                             ;(12)
        bcf     _oDimmer                        ; oDimmer=0(13)

I believe everytime this interrupt will be entered: (Please correct me where I go wrong)
--- Statement (1) in the code will always be true (this is the reason why interrupt has happened), so the code will jump to (9), it will act on (10) & then (11) & (12) -- SO WHERE DOES IT WAIT FOR TIMER0 TO RUN OUT & WHY STATEMENT (13) IS THERE CLEARING _oDimmer when this bit is not set in the sequence I just understood and explained above.

--- When does code enters (5) ? Does after (13) code goes to (3)?

[Kamikaze47]

Statement (1) will not always be true. The interrupt routine services all interrupts. Statements (1)-(4) are just checking which interrupt flag is set (which interrupt went off). If it was the INT interrupt then it jumps to the ZeroCrossingInt section. If it was the TMR0 interrupt then it continues on to the T0Overflow section.

I don't know what else is happening in your program, so I can only tell you what that interrupt routine is doing which is this:

When timer0 overflows: set oDimmer to 1.

When external interrupt (INT) occurs: set timer0 value to "DimmerVal" and set oDimmer to 0.

[financecatalyst]

Statement (1) will not always be true. The interrupt routine services all interrupts. Statements (1)-(4) are just checking which interrupt flag is set (which interrupt went off). If it was the INT interrupt then it jumps to the ZeroCrossingInt section. If it was the TMR0 interrupt then it continues on to the T0Overflow section.

I don't know what else is happening in your program, so I can only tell you what that interrupt routine is doing which is this:

When timer0 overflows: set oDimmer to 1.

When external interrupt (INT) occurs: set timer0 value to "DimmerVal" and set oDimmer to 0.

Is it possible to PM you?