Multiple Interrupts on NUCLEO-L432KC


I need two interrupt pins on a Nucleo-L432KC project (I’m using PwmInRc). The interrupt works when using PA_3, but i’ve tried other pins without success. It doesnt seem to matter if I only use one pin vs. two.

I’ve tested mbed 2 r 172:65be27845400 as well as mbed-os 6691:cf4f12a

I’ve done a fair amount of searching and see that interupts wont work across the same pin number on different ports (so PA_3 and PB_3 wont work). However I’ve tried for instance PA_3 and PB_6 and that doest seem to work. The datasheet seems to say there are 16 interrupt channels on the L432KC.

I’m using the mbed online compiler btw.

Thank you

Using STM32CubeMX i can confirm that PA_1 is assigned to EXTI_1 and PA_6 is assigned to EXTI_6. I’ve been looking thru the InterruptIn.cpp and InterruptIn.h but unfortunately I’m not making headway.

Can you post some code examples? On another ST processor I use, this works fine.

This is the test code I’ve been using. I’ll go back and test this on a breadboard again because i’m paranoid about silly mistakes. I’ve tried various things like external discrete pull-ups as well.

#include "mbed.h"
#include "PwmIn.h"

PwmIn RC1_IN(PA_1);
PwmIn RC2_IN(PA_6);

DigitalOut MYLED(LED1);

int main() {
 while(1) {
    MYLED = 1;
    wait(.50);  // 500 ms
    MYLED = 0; 
    printf("pw %f us   ",RC1_IN.pulsewidth());   
    printf("pw %f us   \r",RC2_IN.pulsewidth());
    wait(.50); // 500 sec


So after more digging, my problem appears to be hardware. On a breadboard, with no external passives (no pullups) i’m able to get the test code to work properly with PA_3 and PA_6.

Thanks for the help, or at least an ear.

Hmm…why didn’t you declare the inputs as interrupts and use them as such? I have not tried to use the PWMIn declaration as you did so I can’t comment on it.

Were you trying to edge detect inputs? I would have tried this declaration


The PwmIn class uses InterruptIn.

The problem was actually and entire bag of bad RC three wire jumpers. On average one of the three cables was bad, causing strange and confusing behavior.