Graham,
You might consider to test if the switch is released. In your code the Loop
will go on for ever if the switch is pressed. Meening the value in CCPR1L
will rapidly go from 0-1-2-...-254-255-0-...

Loop
        btfsc   PORTA,0         ; If switch is not pressed
        goto    Loop            ; don't worry

        movlw   B'00000001'
        addwf   CCPR1L

Loop2
        btfss   PORTA,0         ; Wait until released
        goto    Loop2            ; Loop

        goto Loop

This will not take care of bounces but I saw other answers on this.

Regards
Bjarne Nebelong

-----Original Message-----
From: Graham North [mailto:gs_piclist@HOTMAIL.COM]
Sent: Wednesday, February 07, 2001 7:23 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: [PIC]: PWM problems, HELP!


Hi, if you read my last post you will know that I am
controlling a motor in a pyrometer.

Well I have achieved a PWM output, but am having a few
problems.

I think the motor is 'sending' (right word?!) some noise
to the PIC, I have it running from a seperate supply, but
have had to tie the two grounds together because the FET
needs the source to be zero volts.  I have a diode connected
accross the motor, and decoupling caps everywhere! What
else can I do?

I have also written a piece of code that increases the
duty cycle with a switch press connected to PORTA,0 but
this does not work. I think it is switch bounce causing
this. Is there a way to debounce a switch in S/W? Or is
my code rubbish?

Main
        call    InitPorts
        call    InitPWM

Loop
        btfsc   PORTA,0         ; If switch is not pressed
        goto    Loop            ; don't worry

        movlw   B'00000001'
        addwf   CCPR1L

        goto Loop

This code does not take into account the CP1CON,5 and
CCP1CON,4 bits. Is there a way to increase the duty cycle
in this way, including these bits?

Well thats enough questions now, I hope someone can give
me some answers.

Thanks for your help,

Graham North
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