From: Harold Hallikainen <harold@mai.hallikainen.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Thu, 17 Sep 2020 21:23:12 -0700
Subject: Re: [PIC] Compare Mode
Thread-Topic: [PIC] Compare Mode
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Glad you found the problem!

Harold

> Hi Harold,
> It is indeed phase control. There is a need to switch the output on a
> specific time after the zero cross, but turn it off shortly before the
> next zero cross occurs. I also need to do some other stuff at the mid
> point of each half cycle, hence the multiple CCP use.
>
> While writing this reply I realised my stupid mistake. I had not set the
> CCPx interrupt enables. Things seem to be working correctly now. The
> reason I was getting wacky timing was that the interrupt flags were
> being checked, but only as a by-product of another interrupt sharing the
> same vector. Doh!
> David...
>
> On 18/09/2020 1:27 pm, Harold Hallikainen wrote:
>> This sounds like a phase control light dimmer! I did a four channel one
>> with a single CCP register, figuring out which triac I needed to turn on
>> first, loading the CCP register with that value, then when I got the
>> interrupt, turned on the triac and loaded the CCP register with the next
>> value I needed. I have not looked at that in a long time (more than 10
>> years). I think I started with a 17C42 and ended up using an 18F452. If
>> indeed you're doing a light dimmer, I'd load the CCP registers and clear
>> the timer, and turn off the outputs on a zero cross. Then each CCP
>> interrupt would turn on an output and clear the interrupt flag.
>>
>> This is probably not much help since it's been more than 10 years since
>> I
>> worked on it.
>>
>> Good luck!
>>
>> Harold
>>
>>
>>> I have a PIC16F1828 running from the internal 4MHz oscillator. I use
>>> the
>>> various timers regulatly, but don't recall using the CCP modules
>>> before.
>>> I'm using MPLABX and XC8.
>>>
>>> There is a 100Hz interrupt (INT0) from an optocoupler for zero cross
>>> sync. I've set timer 1 to Fosc/4 and no prescaler, so that should be
>>> ticking over at 1us increments. I'm trying to use CCP1, CCP2 and CCP3
>>> to
>>> get an interrupt at three different points from the zero cross
>>> interrupt.
>>>
>>> CCP1CON is set to 0x0A (compare with interrupt) and CCPR1 is set to
>>> 5000
>>> (decimal) when the INT0 interrupt occurs. I'm clearing a pin when INT0
>>> occurs and setting it when the CCP1IF interrupt is serviced.
>>>
>>> I'm getting a much longer period (LED off time) than the 5ms I
>>> expected.
>>> The timing is not even proportional to the values I enter. Am I missing
>>> something fundamental about how CCP works?
>>>
>>>
>
> --
> ___________________________________________
> David Duffy        Audio Visual Devices P/L
> Unit 8, 10 Hook St, Capalaba 4157 Australia
> Ph: +61 7 38235717      Fax: +61 7 38234717
> Our Web Site: www.audiovisualdevices.com.au
> ___________________________________________
>
> --
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>


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