EXTI pin mapping problem

[shannon2]

Posted on January 26, 2012 at 18:17

It would seem to me given the way the GPIO pins are mapped to EXTI lines, there is no way to use two pins that have the same GPIO pin number.  For example, in my case I would like to use pins A8 and B8 as separate interrupts.  Since all pins with the designation '8' are mapped to the same line, there does not seem to be a way to configure the AFIO_EXTICR registers.

Am I missing something?  As I look at it, it would seem to preclude using the same pin number twice.  If one number is used on one port that pin is excluded on all other ports!

Shannon

[emalund]

Posted on January 26, 2012 at 18:40

that's the way it works

RM0008

Figure 21. External interrupt/event GPIO mapping should eliminate any doub

Erik

It would seem to me given the way the GPIO pins are mapped to EXTI lines, there is no way to use two pins that have the same GPIO pin number.  For example, in my case I would like to use pins A8 and B8 as separate interrupts.  Since all pins with the designation '8' are mapped to the same line, there does not seem to be a way to configure the AFIO_EXTICR registers.

Am I missing something?  As I look at it, it would seem to preclude using the same pin number twice.  If one number is used on one port that pin is excluded on all other ports!

Shannon

[shannon2]

Posted on January 26, 2012 at 18:52

yes I'm familiar with that figure.  I guess I'm alone in thinking it's an unfortunate restriction. I was fishing for a clever work-around.

[emalund]

Posted on January 26, 2012 at 19:53

''restriction'?

i see this as 'flexibility' as opposed to contrallers where interrupt n is pin x, period

Of course a full crossbar would make you (and, probably, some others) happy, however crossbars are HUGE, (I learned this from being involved with another product) , a full crossbar for the routing of inerrupts might easily occupy more silicon thn the ARM core.

Erik

[shannon2]

Posted on January 26, 2012 at 22:09

Yikes.  sorry to step on your feelings.  Didn't mean to imply anything negative about the STM32!  In MY application, in MY circumstances, with MY hardware not being able to use two pins that happen to have the same number IS a restriction.

Before I anger the STM32 gods, let me say its a fantastic processor.  I'm quite happy with it.

Thanks for the help.