code confusion

[Hetal]

hii
i am new to programming and i would like to ask one ques how to code when i want two processes runnign simultaneously. Like i want the pwm to work and the leds to work simultaneously. and it has to loop forever for both of them.

the microchip i am using is pic16f877 and i want the help for the code in assembly language

 

[Nigel Goodwin]

hii
i am new to programming and i would like to ask one ques how to code when i want two processes runnign simultaneously. Like i want the pwm to work and the leds to work simultaneously. and it has to loop forever for both of them.

the microchip i am using is pic16f877 and i want the help for the code in assembly language

You can't do it in software simultaneously, even Pentium 4's don't! - but you can do it sequentially, which is fast enough so you don't notice (which is how a PC multi-tasks - even if somewhat poorly!).

However, the 16F877 has two PWM hardware outputs, these run completely seperate to the processor, so you can just set them and let them run, and use the processor to do something else.

You can check my tutorials for examples of PIC code, including setting the hardware PWM.

 

[philba]

there are many ways to get what you want.

I think you should spend some time learning interrupts. this allows you have code run when it's needed. for example, you can have a timer that interrupts every so often and runs code you wrote to toggle an LED. thus, you don't get stuck in a timing loop for the LED. once your code is run, the processor returns to where it got interrupted.

With interrupts, you can have many things going on "at the same time" even though, as nigel pointed out, all code execution is actually sequential.

 

[Hetal]

thank youll for the advice. However i have checked with interrupts and i read that you can only have one interrupt service routine i already have one for a/d conversion.

here are my two codes. could youll pls help me in how to combine them.

; list p=16F87
;******************************************************************
;* *
;* Filename: 16F877 PWM.asm *
;* Author: hetal *
;* Date: 10-Jun-06 *
;* *
;* PWM program for voltage regulation of buck converter *
;* *
;* Using a 16F877 with 20-MHz clock *
;* *
;* *
;* MPLab: 7.31 *
;* *
;* *
;******************************************************************

;
;
;**************** Program Start ***********************
org 0 ;Reset Vector
goto init
org 4 ;Interrupt Vector
goto int

COUNT equ d'25'

;PWM control

;Setup for PWM operation

; Setting the constants
#include<P16f877.inc>
;**************** Initial Process *********************
init

;***Port Initilisation

bsf STATUS,RP0 ;change to bank 1
movlw b'00000001' ; RA0 and RB0 are inputs
movwf TRISA
movwf TRISB
movwf 00h
movlw TRISC ; all are otuputs
bcf STATUS,RP0

;*** A/D converter initialization

movlw b'10000001' ;ADCS=10 CHS=AN0 ADON=ON
movwf ADCON0

bsf STATUS,RP0 ;move to bank 1
movlw b'00001110' ;ADFM=0 PCFG=1110
movwf ADCON1 ;set adcon1 register
; clrf ADCON1 ;left justified, all input A/D
bcf STATUS, RP0 ;return to bank 0
; movlw 0x41 ;fosc/32 [7-6],A/D on ch0[5-3]

;*** PWM initialization
; Set the PWM period by writing to the PR2 register
; the period chosen is 78.12 khz which is closer to 100khz that was chosen for my buck converter

clrf CCPR1L
clrf TMR2
bsf STATUS,RP0
movlw 3Fh ; value of pr2 calculated came upto be 63
movwf PR2
bcf STATUS,RP0

;Set the PWM duty cycle by writing to the CCPR1L register and CCP1CON<5:4> bits

movlw 26h ; 60 percent duty cycle as the ooutput voltage required is 6 volts and the input is a solar input in the range of
; 7-10 volts. the value of the pwm duty cycle on calculation came to be 153.6 which in 8 bit binary was 26h
movwf CCPR1L
bsf CCP1CON,CCP1Y
bcf CCP1CON,CCP1X

;Make the CCP1 pin an output by clearing the TRISC<2> bit.

bsf STATUS,RP0
movlw fbh
andwf TRISC,f
bcf STATUS,RP0

;set the TMR2 prescale value ad enable Timer2 by writing to T2CON

movlw b'0000100'; the prescaler is 1:1 and setting the tm2on
movwf T2CON


;*** Interruption control
bsf status,rp0 ;Change to Bank1
movlw b'01000100' ;CCP1IE=Enable
movwf pie1 ;Set ADIE and CCP1IE bit register
bcf status,rp0 ;Change to Bank0
movlw b'11000000' ;GIE=ON PEIE=ON
movwf intcon ;Set INTCON register

decfsz
;Interruption wait
;*************** Interruption Process *****************
int
clrf pir1 ;Clear interruption flag


;Start the A/D conversion by setting ADCON0<2>

bsf ADCON0,GO;start the A/D conversion

;Wait until the A/D conversion is done. Bit ADCON0<2> is cleared when
;conversion is done.

Wait:

btfsc ADCON0,GO;wait until conversion is done
goto Wait

;Write the 8 most significant bits located in ADRESH (since we setup the
;registers to be left justified) to port C as an output.

movf ADRESH,W
movwf ccpr1l ;Set Duty cycle of PWM

;************ END of Interruption Process **************
retfie

;configuring the CCP1 module for PWM operation

; movlw 0fh ; 00001111
; movwf CCP1CON




goto Start
end

and the other program is about. three leds blinking. its like a traffic light with the red blinkng first then yellow and green..
my pic is doing both functions pwm operation and led blinking at the same time
; Basic function of switching on and off the LED's
; Setting up the constants

#include<P16f877.inc>

COUNT1 equ 08h
COUNT2 equ 09h


; Setting up the ports

bsf STATUS,5
movlw 00h
movwf TRISA
bcf STATUS,5
; Turning the LED on

Start movlw 02h ; red on
movwf PORTA
; Calling a delay
call Delay
call Delay
call Delay
call Delay
; Turning the Led off after the delay
movlw 04h; yellow on
movwf PORTA
call Delay

movlw 08h; green on
movwf PORTA
call Delay
call Delay
call Delay
call Delay

; Again calling a delay before switching so that it becomes
; visible the switchign on and off of the Led

goto Start



Delay

Loop1 decfsz COUNT1,1
goto Loop1

decfsz COUNT2,1
goto Loop1
return

end




pls need help this assembly language is driving me crazy..

 

[akg]

why all the inits done in a ISR??
the code shouldn't be like this
org 4
goto init

it should be like this
org 4
<register saving>
<isr stuff>
<register restoring>
retfie

the adc module will generate an interrupt after conversion to handle it u need to do it like this
(this part comes in the begining of <isr stuff>

btfsc   PIEx,StatusFlag (say adc int: )
goto    adc_isr_routine
btfsc   <some other checking ,say INT>
goto    int_handler_routine
goto    isr_end
..
..
..
adc_isr_routine
..
..
..
goto isr_end

int_handler_routine
..
..
..
goto isr_end

this is one of the coding method for handling multiple interrupt

 

[Hetal]

thnk u

thnk u for the information.. so basically i just want to clear two things. this interrpt will handle two interrupts does that mean it wwill make my both programs work almost simultaneously.. as i want the led program to work continuously . i heard interrupts usually stop the previous program. andd finishes this first before i go bak to the previous program

so is it better if i just 'call' that function in the begining..

 

[Nigel Goodwin]

I would suggest you re-evaluate your 'need' for interrupts, I think you're just confusing your self! - as 'akg' mentioned you're not even using them correctly.

It's often possible to do it all in a software loop, then, perhaps later, use interrupts for one or two of the functions.

If you tell us what you're wanting to do, we can make suggestions as to what might be best?, but you do need to give all the details!.

 

[motion]

Here is how I would re-arrange your code. I did not check for bugs and so it is nowhere near running condition. I understand what you are trying to achieve and below are some more comments.

        list p=16F877
;************************************************* *****************
;* *
;* Filename: 16F877 PWM.asm *
;* Author: hetal *
;* Date: 10-Jun-06 *
;* *
;* PWM program for voltage regulation of buck converter *
;* *
;* Using a 16F877 with 20-MHz clock *
;* *
;* *
;* MPLab: 7.31 *
;* *
;* *
;************************************************* *****************
; Setting the constants
        #include<P16f877.inc>
COUNT equ d'25'
;
;
;**************** Program Start ***********************
        org 0 ;Reset Vector
        goto init
        org 4 ;Interrupt Vector
;       goto int
;Interruption wait
;*************** Interruption Process *****************
;PWM control 
int:
        SAVE_CONTEXT
        clrf pir1 ;Clear interruption flag
        btfsc ADCON0,GO;wait until conversion is done
        goto Wait
;Write the 8 most significant bits located in ADRESH (since we setup the
;registers to be left justified) to port C as an output.
        movf ADRESH,W
        movwf ccpr1l ;Set Duty cycle of PWM
;Start the A/D conversion by setting ADCON0<2>
        bsf ADCON0,GO;start the A/D conversion
;************ END of Interruption Process **************
Wait:
        LOAD_CONTEXT
        retfie
;Setup for PWM operation 
;**************** Initial Process *********************
init:
;***Port Initilisation
        bsf STATUS,RP0 ;change to bank 1 
        movlw b'00000001' ; RA0 and RB0 are inputs 
        movwf TRISA
        movwf TRISB
        movwf 00h
        movlw TRISC ; all are otuputs 
        bcf STATUS,RP0
;*** A/D converter initialization
        movlw b'10000001' ;ADCS=10 CHS=AN0 ADON=ON
        movwf ADCON0
        bsf STATUS,RP0 ;move to bank 1
        movlw b'00001110' ;ADFM=0 PCFG=1110
        movwf ADCON1 ;set adcon1 register
;       clrf ADCON1 ;left justified, all input A/D
        bcf STATUS, RP0 ;return to bank 0
;       movlw 0x41 ;fosc/32 [7-6],A/D on ch0[5-3]
;*** PWM initialization
; Set the PWM period by writing to the PR2 register 
; the period chosen is 78.12 khz which is closer to 100khz that was chosen for my buck converter
;configuring the CCP1 module for PWM operation
        movlw 0fh ; 00001111
        movwf CCP1CON
        clrf TMR2
        bsf STATUS,RP0
        movlw 3Fh ; value of pr2 calculated came upto be 63
        movwf PR2
        bcf STATUS,RP0
;Set the PWM duty cycle by writing to the CCPR1L register and CCP1CON<5:4> bits
        movlw 26h ; 60 percent duty cycle as the ooutput voltage required is 6 volts and the input is a solar input in the range of 
; 7-10 volts. the value of the pwm duty cycle on calculation came to be 153.6 which in 8 bit binary was 26h
        movwf CCPR1L
        bsf CCP1CON,CCP1Y
        bcf CCP1CON,CCP1X
;Make the CCP1 pin an output by clearing the TRISC<2> bit.
        bsf STATUS,RP0
        movlw fbh
        andwf TRISC,f
        bcf STATUS,RP0 
;set the TMR2 prescale value ad enable Timer2 by writing to T2CON
        movlw b'0000100'; the prescaler is 1:1 and setting the tm2on
        movwf T2CON 
;*** Interruption control
        bsf status,rp0  ;Change to Bank1
        movlw b'01000000' ; ADIE=Enable
        movwf pie1 ;Set ADIE and CCP1IE bit register
        bcf status,rp0 ;Change to Bank0
        movlw b'11000000' ;GIE=ON PEIE=ON
        movwf intcon ;Set INTCON register
; Setting up the ports 
        bsf STATUS,5
        movlw 00h
        movwf TRISA
        bcf STATUS,5
        bsf ADCON0,GO;start the A/D conversion
;****************************************************
Start:
; Turning the LED on 
        movlw 02h ; red on
        movwf PORTA
; Calling a delay
        call Delay
        call Delay
        call Delay
        call Delay
; Turning the Led off after the delay
        movlw 04h; yellow on
        movwf PORTA
        call Delay
        movlw 08h; green on
        movwf PORTA
        call Delay
        call Delay
        call Delay
        call Delay
; Again calling a delay before switching so that it becomes
; visible the switchign on and off of the Led 
        goto Start
        end

1. Although, this PIC can only have one interrupt routine, it can handle more than one interrupt source by checking the PIR1 for the source of interrupt.

2. I don't think CCP1IE and CCP1IF works with the CCP PWM mode. The PIC16F877 documentation is silent on this. However, you can use TMR2IE and TMR2IF with PWM. This interrupt occurs at 78.12Khz rate which may be too fast. You can postscale it from 1:2 to 1:4 (39.06Khz, 26.04Khz and 19.53Khz respectively). If you use timer2 as interrupt source, you can periodically (once every 38.4usec @ 26Khz) start an A/D conversion inside the ISR. The conversion will be finished in 19.2usec,allowing 19.2usec remaining time for data acquisition.

3. Alternatively, you can use the speed of the A/D converter to determine how fast you update the duty cycle registers. If you use ADIF to trigger an interrupt, you have to insert a short 10-20usec acquisition time delay before starting a new conversion. I would recommend using timer2 triggered interrupts instead.

4. You have to save/restore context in the ISR. See the datasheet.

 

[Hetal]

my program details

I would suggest you re-evaluate your 'need' for interrupts, I think you're just confusing your self! - as 'akg' mentioned you're not even using them correctly.

It's often possible to do it all in a software loop, then, perhaps later, use interrupts for one or two of the functions.

If you tell us what you're wanting to do, we can make suggestions as to what might be best?, but you do need to give all the details!.

hi sorry for not including the details

my project overall involves..solar powere traffic light control.

so in my proj. we are stepping down the voltage by buck converter and then usng the microchip to regulate a 6v output and use the mocrochip for switching on the leds in a traffic light manner .

so the microchips basic function is

pwm and analog to digital conversion to get an output of 6v

leds to work from red to yellow to green

my code is a combination of a codes i checked online.. i am pretty new to this language so i am learnign by cheking some codes online and trying to understand them .

thnk u for ur help

 

[Hetal]

still dont understand

Here is how I would re-arrange your code. I did not check for bugs and so it is nowhere near running condition. I understand what you are trying to achieve and below are some more comments.

        list p=16F877
;************************************************* *****************
;* *
;* Filename: 16F877 PWM.asm *
;* Author: hetal *
;* Date: 10-Jun-06 *
;* *
;* PWM program for voltage regulation of buck converter *
;* *
;* Using a 16F877 with 20-MHz clock *
;* *
;* *
;* MPLab: 7.31 *
;* *
;* *
;************************************************* *****************
; Setting the constants
        #include<P16f877.inc>
COUNT equ d'25'
;
;
;**************** Program Start ***********************
        org 0 ;Reset Vector
        goto init
        org 4 ;Interrupt Vector
;       goto int
;Interruption wait
;*************** Interruption Process *****************
;PWM control 
int:
        SAVE_CONTEXT
        clrf pir1 ;Clear interruption flag
        btfsc ADCON0,GO;wait until conversion is done
        goto Wait
;Write the 8 most significant bits located in ADRESH (since we setup the
;registers to be left justified) to port C as an output.
        movf ADRESH,W
        movwf ccpr1l ;Set Duty cycle of PWM
;Start the A/D conversion by setting ADCON0<2>
        bsf ADCON0,GO;start the A/D conversion
;************ END of Interruption Process **************
Wait:
        LOAD_CONTEXT
        retfie
;Setup for PWM operation 
;**************** Initial Process *********************
init:
;***Port Initilisation
        bsf STATUS,RP0 ;change to bank 1 
        movlw b'00000001' ; RA0 and RB0 are inputs 
        movwf TRISA
        movwf TRISB
        movwf 00h
        movlw TRISC ; all are otuputs 
        bcf STATUS,RP0
;*** A/D converter initialization
        movlw b'10000001' ;ADCS=10 CHS=AN0 ADON=ON
        movwf ADCON0
        bsf STATUS,RP0 ;move to bank 1
        movlw b'00001110' ;ADFM=0 PCFG=1110
        movwf ADCON1 ;set adcon1 register
;       clrf ADCON1 ;left justified, all input A/D
        bcf STATUS, RP0 ;return to bank 0
;       movlw 0x41 ;fosc/32 [7-6],A/D on ch0[5-3]
;*** PWM initialization
; Set the PWM period by writing to the PR2 register 
; the period chosen is 78.12 khz which is closer to 100khz that was chosen for my buck converter
;configuring the CCP1 module for PWM operation
        movlw 0fh ; 00001111
        movwf CCP1CON
        clrf TMR2
        bsf STATUS,RP0
        movlw 3Fh ; value of pr2 calculated came upto be 63
        movwf PR2
        bcf STATUS,RP0
;Set the PWM duty cycle by writing to the CCPR1L register and CCP1CON<5:4> bits
        movlw 26h ; 60 percent duty cycle as the ooutput voltage required is 6 volts and the input is a solar input in the range of 
; 7-10 volts. the value of the pwm duty cycle on calculation came to be 153.6 which in 8 bit binary was 26h
        movwf CCPR1L
        bsf CCP1CON,CCP1Y
        bcf CCP1CON,CCP1X
;Make the CCP1 pin an output by clearing the TRISC<2> bit.
        bsf STATUS,RP0
        movlw fbh
        andwf TRISC,f
        bcf STATUS,RP0 
;set the TMR2 prescale value ad enable Timer2 by writing to T2CON
        movlw b'0000100'; the prescaler is 1:1 and setting the tm2on
        movwf T2CON 
;*** Interruption control
        bsf status,rp0  ;Change to Bank1
        movlw b'01000000' ; ADIE=Enable
        movwf pie1 ;Set ADIE and CCP1IE bit register
        bcf status,rp0 ;Change to Bank0
        movlw b'11000000' ;GIE=ON PEIE=ON
        movwf intcon ;Set INTCON register
; Setting up the ports 
        bsf STATUS,5
        movlw 00h
        movwf TRISA
        bcf STATUS,5
        bsf ADCON0,GO;start the A/D conversion
;****************************************************
Start:
; Turning the LED on 
        movlw 02h ; red on
        movwf PORTA
; Calling a delay
        call Delay
        call Delay
        call Delay
        call Delay
; Turning the Led off after the delay
        movlw 04h; yellow on
        movwf PORTA
        call Delay
        movlw 08h; green on
        movwf PORTA
        call Delay
        call Delay
        call Delay
        call Delay
; Again calling a delay before switching so that it becomes
; visible the switchign on and off of the Led 
        goto Start
        end

1. Although, this PIC can only have one interrupt routine, it can handle more than one interrupt source by checking the PIR1 for the source of interrupt.

2. I don't think CCP1IE and CCP1IF works with the CCP PWM mode. The PIC16F877 documentation is silent on this. However, you can use TMR2IE and TMR2IF with PWM. This interrupt occurs at 78.12Khz rate which may be too fast. You can postscale it from 1:2 to 1:4 (39.06Khz, 26.04Khz and 19.53Khz respectively). If you use timer2 as interrupt source, you can periodically (once every 38.4usec @ 26Khz) start an A/D conversion inside the ISR. The conversion will be finished in 19.2usec,allowing 19.2usec remaining time for data acquisition.

3. Alternatively, you can use the speed of the A/D converter to determine how fast you update the duty cycle registers. If you use ADIF to trigger an interrupt, you have to insert a short 10-20usec acquisition time delay before starting a new conversion. I would recommend using timer2 triggered interrupts instead.

4. You have to save/restore context in the ISR. See the datasheet.

thanks for the information. i am sorry but i did not understand ur points 2 3 and 4 as i am new to programming.. all i did was copy this code from another analog to digital conversion and i understood only tht part of the code.
i know i have to include an interrupton wait tht i have forgotten to include.

if you could explain to me in the form of a code would be of great help . thanks

 

[Nigel Goodwin]

hi sorry for not including the details

my project overall involves..solar powere traffic light control.

so in my proj. we are stepping down the voltage by buck converter and then usng the microchip to regulate a 6v output and use the mocrochip for switching on the leds in a traffic light manner .

so the microchips basic function is

pwm and analog to digital conversion to get an output of 6v

leds to work from red to yellow to green

For a start I would get the buck converter running, no need to worry about the traffic light part which is pretty trivial.

So setup the PWM module, details are in my PWM tutorial, then have a simple loop, reading the analogue input, and adjusting the PWM value accordingly - you will probably need a time delay before you loop back and read the analogue input again. You might also try taking multiple analogue readings and averaging them?.

Once that's working OK, and you've tested it under various loads, you could start adding the traffic light section. You could do it all in a single software loop, along with the buck converter, a PIC is more than capable of everything you want without using interrupts. However, I would suggest using a timer interrupt (personally I'd use timer2), and control the traffic lights within the interrupt routine.

The thing to remember is that the PWM is done entirely by the hardware, you tell it what mark/space ratio you want and it will continue doing that entirely independently while you go and do something else - this is a true 'simultaneous' process, as it's seperate hardware (although inside the PIC).

 

[Hetal]

pwm or a/d?

For a start I would get the buck converter running, no need to worry about the traffic light part which is pretty trivial.

So setup the PWM module, details are in my PWM tutorial, then have a simple loop, reading the analogue input, and adjusting the PWM value accordingly - you will probably need a time delay before you loop back and read the analogue input again. You might also try taking multiple analogue readings and averaging them?.

Once that's working OK, and you've tested it under various loads, you could start adding the traffic light section. You could do it all in a single software loop, along with the buck converter, a PIC is more than capable of everything you want without using interrupts. However, I would suggest using a timer interrupt (personally I'd use timer2), and control the traffic lights within the interrupt routine.

The thing to remember is that the PWM is done entirely by the hardware, you tell it what mark/space ratio you want and it will continue doing that entirely independently while you go and do something else - this is a true 'simultaneous' process, as it's seperate hardware (although inside the PIC).

thanks for the info. i am looking into how to use timer interrupts now. moreover for the converter write now we are fixing the duty cycle to be 60 percent , so i dont need to worry about that. however my question arises onn that pwm is enough? i dont need to bother about analog to digital conversion.???? i checked your code on pwm and i am making some modifications accordingly.

 

[Nigel Goodwin]

thanks for the info. i am looking into how to use timer interrupts now. moreover for the converter write now we are fixing the duty cycle to be 60 percent , so i dont need to worry about that. however my question arises onn that pwm is enough? i dont need to bother about analog to digital conversion.???? i checked your code on pwm and i am making some modifications accordingly.

If you just want a fixed 60% PWM, then you don't need the analogue to digital conversion.

For a timer interrupt example, check my seven segment tutorial, where I use timer2 interrupts to multiplex the display.

 

[Hetal]

timer2?

If you just want a fixed 60% PWM, then you don't need the analogue to digital conversion.

For a timer interrupt example, check my seven segment tutorial, where I use timer2 interrupts to multiplex the display.

hi Nigel

thnks for the information . i have my Pwm code now working fine and i was reading through the tutorial 10 for the seven segment display. However,i dint get much out of it. but i want to confirm with you what i am thinking is it right.

the interrupt will basically kepp my led running all the time along with the pwm happenign this is a small code that i have developed. could u look into it and confirm with me if i am thinking right in enabling the code and the use of the whole thing.. i have attached the code for your review and comments.. thnks a lot

 

[Nigel Goodwin]

Sorry, but your code makes NO sense at all? - for a start you have no context saving or restoring in the interrupt routine, and you don't even have an 'RETFIE' for it to return from the interrupt.

You also appear to be trying to initialise things in the interrupt routine?, this should all be done in the main program.

Why are you refering to PWM in the interrupt routine?, the PWM is completely transparent - set it to 60% in the main routine initialisation and forget about it!.

 

[Hetal]

I am sorry

..oh sorry nigel i was trying to mix codes. now i have finally understood the code and also by looking through your tutorial ,i have come witht his final code.

i have initialised in the main routine the pwm port and the interrrupt control bits and for the itnerruption proces.. i have used the led working

thanks for ur help

 

[Nigel Goodwin]

..oh sorry nigel i was trying to mix codes. now i have finally understood the code and also by looking through your tutorial ,i have come witht his final code.

i have initialised in the main routine the pwm port and the interrrupt control bits and for the itnerruption proces.. i have used the led working

thanks for ur help

I'm still very confused by what's supposed to be going on?.

For example:

PWM_PERIOD_MATCH
    btfss   PIR1,TMR2IF      ;test on the trm2 interrupt flag
    goto    PWM_PERIOD_MATCH  ; if reset keep checking
    bcf     PIR1,TMR2IF       ; if set reset the flag
    goto    wait


wait NOP
     return

What's that supposed to be doing?, and why does it have a 'return' at the end when it never appears to have been 'called' as a subroutine?. This will almost certainly just make the program crash.

You still don't appear to understand the use of interrupts either (although at least you are now saving and restoring registers).

The general idea of an interrupt routine is that it's very short and fast, you're calling loads of delay routines in yours - this isn't good practice, and should be discouraged.

So, a couple of basic questions:

1) Whats the main program supposed to be doing?.

2) What's the interrupt routine supposed to be doing?.

3) Extra one - why interrupts at all?.

 

[Hetal]

questions...

1) Whats the main program supposed to be doing?.

the main program is initialising the ports and its helping for my pwm .. so basically i am doing my pwm of 60 percent duty cycle in the main program.



2) What's the interrupt routine supposed to be doing?.

well u mentioned to me previously to use interrupts .. the timer2 interrupts. so was it for my LEDS that i will be using. ?


3) Extra one - why interrupts at all?.

well i dont know i had aproblem of using two programs as i mentioned i want my LED to be workign as a traffic light... inconsequential of wht happens to my pwm output and i also want pwm to be working

so incase if i am not using interrupts can ijust include the code by calling a subroutine.. will it work continuously that was my question....

 

[Nigel Goodwin]

1) Whats the main program supposed to be doing?.

the main program is initialising the ports and its helping for my pwm .. so basically i am doing my pwm of 60 percent duty cycle in the main program.

How is it 'helping' your PWM?. You were wanting a fixed 60% PWM, simply initialise the PWM at 60% and forget it - the PWM hardware does everything on it's own.

2) What's the interrupt routine supposed to be doing?.

well u mentioned to me previously to use interrupts .. the timer2 interrupts. so was it for my LEDS that i will be using. ?

I only said to use interrupts IF needed, and in the right way - you appear to have no need for them at all?.

3) Extra one - why interrupts at all?.

well i dont know i had aproblem of using two programs as i mentioned i want my LED to be workign as a traffic light... inconsequential of wht happens to my pwm output and i also want pwm to be working

so incase if i am not using interrupts can ijust include the code by calling a subroutine.. will it work continuously that was my question....

As a very crude 'example' all you need is something like this:

Initalise PIC
Set PWM to 60%
Loop
    Set Traffic lights to 1
    Call delay
    Set Traffic lights to 2
    Call delay
    Set Traffic lights to 3
    Call delay
Goto Loop

Where 1, 2, and 3 set the patterns of lights you need, if you need more than three patterns then add extra sections as required. Obviously you will probably require different time delays during the sequence, so you could call different delays, or the same delay more than once.

 

[Hetal]

hehe

well but its funny tht was a simple code and all this while i was trying al the hard stuff..

aneways i guess this way i learnt how to .. do a/d conversion and timer interrupts.. soo a quick question though .. when is the actual need for an interrupt can u give me a good example..

thnks a lot for the time and effort u took to help me for the code.... really appreciated.. now i feel from a person who knew nothing about the assembly language seems to .. understand