Posted on January 15, 2014 at 16:42Here is an odd find.. if I change the code slightly:
volatile unsigned int poop = 0;
void tim2_isr ( void ) {
//gpio_clear ( GPIOC, GPIO3 );
//TIM2_SR &= ~TIM_SR_UIF; //clearing update interrupt flag
TIM_SR(TIM2) &= ~TIM_SR_UIF; /* Clear interrrupt flag. */
#if 1
poop = 1;
#endif
gpio_toggle(GPIOC, GPIO3); /* LED on/off. */
}
Note:
- if the 'clearing update' is at the bottom (where it was, where I would expect it should be), no luck; moving it up the top of function, and it may work..
- .. but only if the volatile is kept (and is now unused.)
main loop now just does 'if poop, poop = 0' with its gpio toggle commented out.
If I remove the volatile 'poop' (sorry, it was late) entirely, no joy.
Let me try adding some other fluff .. I wonder if somehow there is a minimum size thing here, or a 'it needs to run just a bit longer', or something .. or maybe the interupt is triggering twice in a row, then waiting a secon, then twicfe, etc, so as to cancel itself out or something..
edit: yesm, just adding a few delay NOPs in place, makes it happy. Still have to have the 'clearing interupt' at the first thing though:
void tim2_isr ( void ) {
//TIM2_SR &= ~TIM_SR_UIF; //clearing update interrupt flag
TIM_SR(TIM2) &= ~TIM_SR_UIF; /* Clear interrrupt flag. */
unsigned long int j;
for ( j = 0; j < 100; j++ ) {
__asm__(''nop'');
}
gpio_toggle(GPIOC, GPIO3); /* LED on/off. */
}
... so weird. Is it being double-called and thus needing to block itself, or is there some minimum duration requirement here?!
🙂
