Jinx wrote:
>> Is it generally ok to have about 30 lines of code inside the interrupt
>> routine?
>>     
>
> Stephen, hi, you can have as many lines of code as you like inside
> an ISR. The only proviso is that, generally, if you are expecting
> another interrupt, the current interrupt processing is finished. Or
> at least left in a state that you can return to if, for example, a higher
> priority or other interrupt/event needs processing first
>
> <<clipped>>
Thanks for the enlightenment!
Most ISR info I see says to keep it as short as possible but, in my 
design, the only other thing going on aside from the code in the ISR is 
timer1's interrupt which is required for the delay. I am doing a hobby 
robot controller using 2 PWM channels for differential drive. Main 
routine calls a ramp up routine which increments both PDC registers to a 
preset max value using timer1 running to match the timer1 period reg and 
interrupt in between each increment. When one of the IR sensors sees and 
obstacle at a preset distance, it provides a switched logic level to 
INT0 or INT1 external interrupt pins (left or right sensor). My INT0 and 
INT1 ISR's will decrement one of the PDC regs with the same timer1 delay 
to provide a ramp down of the appropriate motor causing the bot to 
smoothly turn away from the obstacle until the external interrupt pin is 
no longer true. Then the same PDC reg is incremented back to where it 
originally was, again using the timer1 delay. At thins point, the ISR is 
done and returns control to the main loop.

-- 
Regards,
Stephen D. Barnes

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