10 years, 1 month ago.

Attaching interrupt to pins other than PC_13

I am not understanding the behavior of my F401RE. The following code:

#include "mbed.h"

DigitalOut  my_led(LED1);
InterruptIn my_button(PC_13); // Button
//InterruptIn my_button(PC_9); 

int presses = 0;

void pressed()
{
    presses++;
}

int main()
{
    my_led=1; // let me know main() is running
    wait(0.5);
    my_led=0;
 
    my_button.mode(PullUp);
    my_button.fall(&pressed);
    
    while (1) {
        for(int i=0; i<presses; i++) {
            my_led=1;
            wait(0.2);
            my_led=0;
            wait(0.2);
        }
        wait(0.5);
    }
}

This code works as expected. After reset is released, the board LED lights briefly, and then blinks once for each time the user button is pressed.

However, if I uncomment the assignment of the interrupt to PC_9 (and obviously comment out the assignment to PC_13), Nothing happens. I have a physical 1k pullup resistor on PC_9. The LED never lights to tell me main() has started, and never blinks no matter how many times I press a button to short PC_9 to GND.

I've tried this same experiment on a few pins - PC_8, PC_7, and some more I don't remember. The interrupt only seems to work properly on PC_13. What am I missing?

Thanks in advance.

Question relating to:

Last updated: 20 Apr 2021

NUCLEO-F401RE

Affordable and flexible platform to ease prototyping using a STM32F401RET6 microcontroller.