[Icc-avr] Interrupt Help Please (Happy New Year)

[John Baraclough]

Hi Johannes,

Actually page 84 of the AT90USB162 data sheet says:

/*When the external interrupt is enabled and is configured as level 
triggered, the interrupt will trigger as long as the pin is held low. 
Note that recognition of falling or rising edge interrupts on INT7:4 
requires the presence of an I/O clock, described in “System Clock and 
Clock Options” on page 25. Low level interrupts and the edge interrupt 
on INT3:0 are detected asynchronously. This implies that these 
interrupts can be used for waking the part also from sleep modes other 
than Idle mode. The I/O clock is halted in all sleep modes except Idle 
mode.*
/
So INT7..4 can only wake up the part from all sleep modes if it is used 
as a level interrupt and that level is maintained until the part has 
completed the wake-up. INT3..0 can be used as edge or level triggered 
interrupts to wake up the part from all sleep modes as they are detected 
asynchronously.

INT1 cannot be used as a pin-change interrupt, but must be programmed to 
respond to a defined edge or level. According to Andrew's specification 
in his original post this is fine. At startup, first check that the 
level is not high already and then set the interrupt to respond to a 
rising edge. If you don't do the first check then the interrupt may 
never be triggered. When a rising edge is detected, in the ISR reset the 
interrupt to respond to a falling edge and set a semaphore for 'main()' 
that indicates the edge has been seen. 'main()' must then tidy up 
everything before executing the 'sleep' command.

HTH

All the best for now,
John


Johannes Assenbaum wrote:
> Hi Andrew,
>
> as datasheet tells, only INT7..4 level interrupts are able to wake up CPU from sleep mode other than idle.
>
> As I understand, this will not fit your needs.
>
> Best regards,
> Johannes
>
>