DT-Interrupts - Is there a clash between ExtInt and IntOnChange?

[richard]

generally the best solution is to absolute minimum processing in the isr like set a flag to indicate to main code that a task must be performed

ie
your triac isr can hold processing up for over 6mS
you could instead use zero cross to start another timer for "speed delay" that timer can then cause an interrupt to fire triac
both of these isr's could be very simple and done as asm type for absolute minimum overhead.
the "ir" isr could similarly start a timer and reset for another edge trigger set state 1. with the timer set for a period greater than the ir start pulse time
if the timer int goes off then its a false trigger if the timer value is to low when the edge triggers then its a false trigger otherwise
for a good trigger set a state so the foreground processing can decode the ir stream.
this would be a state managed process
state 0 ir idle
state 1 ir active
state 2 ir start pulse detected ,manage in foreground
it can all be done in uS no bogging down with delays

[Balachandar]

Thank you Richard, for the suggestions. I will try and implement whatever I can.

I haven't written any code in Asm so far. I guess, when it comes to using multiple interrupts, learning to code in Asm may be a necessity.

What about using a second PIC for the Elapsed Timer with a common clock? Is it worth trying?

- Bala

[richard]

i doubt its really necessary , it still leaves the issue of transferring data between chips with lots of isr's running

[Ioannis]

The tricky part as I see it, under Richard's directions, is the processing of ir in the foreground. But states will help, as long as your routines are fast enough.

Better start with one task at the time and if it works ok, add another. All together might complex things and prevent debugging.

Ioannis

[mpgmike]

Here's a crazy thought; if you have 2 interrupts doing virtually the same thing, why not do both functions with only 1 interrupt? If your 100 Hz mains interrupt is clocking the same as your Timer 1, can you put your Timer 1 code in your ExtInt interrupt?

[Ioannis]

With 100Hz, I think there is a lot of time for this. Have done much worse things in ISR!

Ioannis

[Balachandar]

With 100Hz, I think there is a lot of time for this. Have done much worse things in ISR!

Ioannis

You are right Ioannis. With 100Hz, there is a lot of time. It's all a question of what needs to be done by the ISR and how quickly it can be done.

- Bala

[Balachandar]

Here's a crazy thought; if you have 2 interrupts doing virtually the same thing, why not do both functions with only 1 interrupt? If your 100 Hz mains interrupt is clocking the same as your Timer 1, can you put your Timer 1 code in your ExtInt interrupt?

Your thought is not at all crazy; it's quite logical.

Both IOC Int for firing the triac and Timer1 Int for the Elapsed Timer occur 100 times per second. But I cannot use the Timer1 Int for the triac since the timing should be in sync with the zero crossings of the mains. It is possible to use the zero crossings for keeping time, but the timing accuracy may not be satisfactory.

But coming to think of it, if the timer accuracy is + or - 10% it is still good enough for me.
Thanks mpgmike. Based on your suggestion, I will try out using IOC Int for both firing the triac and the Elapsed Timer.

- Bala