Instant Interrupts - Revisited

[sougata]

Hi,

It is very unlikely that DT's int handler mess with your CCP2CON register. Do you have a LCD / Serial / Debug out then try dumping the CCP2COn values periodically to know whats going on.

A look at the code may be helpful. I have 18F4520 ready with me and would like to duplicate the problem for my own interest.

[alanmcf]

Hi sougata--

The code is massive, with a dozen include files... it would be a real mess to upload it. PWM on channel 1 always works. I have discovered since I posted that message that if I start Timer1 (T1CON.0 = 1, the timer that is used by Darrell's Elapsed Timer code), then the PWM on channel 2 works. Stop timer 1, and channel 2 PWM stops working. But if I comment out all of Darrell's code and recompile, both PWM ports work perfectly.

PWM only uses Timer 2, so I am baffled. I do have an LCD attached, I will try reading the CCP2CON register and see what its thinking.

Thanks--

--Alan

[Bruce]

I think the default for channel 2 is Timer1 unless you use the DEFINE HPWM2_TIMER 2 option.
Channel 1 defaults to Timer2 so you would still see this channel working when disabling Timer1.

See if adding DEFINE HPWM2_TIMER 2 doesn't cure the problem.

Edit: Scratch that one. This is apparantly only for 17C7xx device types.

[Darrel Taylor]

Well, without the code, we're reduced to playing 20 questions.

Please post at least the Interrupt Definitions, handlers (other than Elapsed), and ANY and ALL lines that modify the following registers.

T1CON
INTCON
INTCON2
INTCON3

PIE1
PIE2
IPR1
IPR2

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[sougata]

Hi,

DT's Elapsed Timer takes care of setting T1CON right in the "StartTimer" . If by any means T1CON oscillator is turned on then PORTC.1 becomes an input regardless of the TRIS settings. Still it does not explain why and how the PWM starts when Timer1 is started.

What happens when your PWM stops the pin in set low/high ?
I hope you are quite aware that if duty cycle is higher than period then the pin never gets cleared.

Mr.E where is your crystal ball ??!!??

[Darrel Taylor]

If by any means T1CON oscillator is turned on then PORTC.1 becomes an input regardless of the TRIS settings.

That's a good possibility.

Still it does not explain why and how the PWM starts when Timer1 is started.

So True!

> Mr.E where is your crystal ball ??!!??
Ummm, being that he hasn't logged in since 15th June 2008
I'd say he's in Jail.

Can't imagine mister-e not checking in, if he could.
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[alanmcf]

Hmmm... Sougata's point about starting timer1 sounds like it might be the culprit, at least as far as RC1 going to input. PWM2 drives a fan via a MOSFET, so if RC1 goes to input, the pullup I have on the MOSFET would drive the fan to full speed, which is exactly what's happening. I haven't yet found in the data sheet why turning timer1 on does that to RC1.

I have attached the code relevant to Darrel's question. The INCLUDE files that aren't attached don't modify the registers Darrel was talking about. I have very little experience with using the timers or using interrupts-- is it possible to just modify the Elapsed Timer routine to use timer 0 or timer3?

Thanks--

--Alan

[Ioannis]

Can't imagine mister-e not checking in, if he could.
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In fact, I had some tel. discussion 1 and 1/2 month ago with Steve, but when I tried to find him again, he disappeared. No telephones (only tel. answering machine) no e-mails. If anyone knows about Steve please inform. He had some misfortunes in the past as we can recall, just hope all is OK now, lying in some beach.

Ioannis