AVR-Chat

--- In AVR-Chat@yahoogroups.com, John Samperi <samperi@...> wrote:
>
> 
> If INT1 routine or ANY OTHER interrupts routine is running
> then nothing else can stop that routine UNLESS you reenable
> interrupts within the INT1 routine which is VERY DANGEROUS
> unless you handle it properly.
> 
> You can get INT1 (and INT0) to simply set a flag and exit and
> then you handle their service in the main loop, this way if another
> int happens it can be serviced suspending the current service.
> 
> STILL IT CAN GET VERY MESSY unless handled properly.
> 
> By the way I hope you have RETIs in your interrupts routines.
> 
> Regards
> 
> John Samperi
> 

John
Thanks for responding.

How does the AVR do this internally - is the mcu is executing it's 
own form of "CLI"? Or is it just turning off the Enable flags for 
INT0 and INT1?

In my case, what I'm doing is making a PCB drill, and a debounced 
footswitch is attached to INT1. That kicks off a single drill cycle 
that runs a slide up and down using a stepper. At the end of the INT1 
ISR, I'm hitting the EIFR register to clear the INT1 flag. This 
prevents a second cycle unless the first cycle has ended, in case I 
accidently press the footswitch again in the middle of the cycle. 

The INT0 switch is a KILL / Emergency switch, so it's response MUST 
be immediate - in case I'm about to drill my finger, etc. A pc of 
broken .025" carbide in my finger is not my idea of fun.

I like your idea of jumping right back out of the ISR's, and having a 
master routine handle all of the switches. I'll have to see if that 
will work in my code.

I can see how it could get messy, but in my case, when the KILL 
switch is executed, I want it to jump to the INT0 ISR, and stay in 
there in an endless loop until I reset the CPU. I have an error LED 
that flashes in the INT0 ISR.

Randy