Enable external interrupts ARM Cortex-M0+ (STM32G070) - c

Question

I'm trying to get a fundamental understanding of programming for STM32 microcontrollers. I'm trying to use an external interrupt from a button to toggle the state of an LED, by setting all the appropriate registers (no external libraries/definitions). I can't seem to get the interrupt routine to work, control is never passed to the handler.
Here's what I'm using to set PC-13 (to which there is a button attached as per the Nucleo-G070RB board) as an external interrupt:
RCC_APBENR2 |= 0b1 << 0; // Enable SYSCFGEN
RCC_IOPENR |= 0b1 << 2; // Enable PORTC
EXTI_RTSR1 |= 0b1 << 13; // Enable interrupt on rising edge at EXTI line 13
EXTI_EXTICR4 |= 0x2 << 8; // Set PC-13 as GPIO pin for interrupt
EXTI_IMR1 |= 0x1 << 13; // Unmask EXTI line 13
NVIC_ISER |= 0b1 << 7; // Enable interrupts for EXTI4_15
I'm not sure what I'm missing.
Here's the full code:
#include <stdint.h>
#include <stdio.h>
#define RCC_IOPENR *((uint32_t volatile *) 0x40021034)
#define RCC_APBENR2 *((uint32_t volatile *) 0x40021040)
#define GPIOA_MODER *((uint32_t volatile *) 0x50000000)
#define GPIOA_IDR *((uint32_t volatile *) 0x50000010)
#define GPIOA_ODR *((uint32_t volatile *) 0x50000014)
#define GPIOC_MODER *((uint32_t volatile *) 0x50000800)
#define GPIOC_IDR *((uint32_t volatile *) 0x50000810)
#define GPIOC_ODR *((uint32_t volatile *) 0x50000814)
#define NVIC_ISER *((uint32_t volatile *) 0xE000E100)
#define EXTI_RTSR1 *((uint32_t volatile *) 0x40021800)
#define EXTI_EXTICR1 *((uint32_t volatile *) (0x40021800 + 0x060 + 0x4 * 0))
#define EXTI_EXTICR2 *((uint32_t volatile *) (0x40021800 + 0x060 + 0x4 * 1))
#define EXTI_EXTICR3 *((uint32_t volatile *) (0x40021800 + 0x060 + 0x4 * 2))
#define EXTI_EXTICR4 *((uint32_t volatile *) (0x40021800 + 0x060 + 0x4 * 3))
#define EXTI_IMR1 *((uint32_t volatile *) (0x40021800 + 0x080))
#define EXTI_RPR1 *((uint32_t volatile *) (0x40021800 + 0x00C))
void button_init();
extern void initialise_monitor_handles();
uint8_t volatile g_button_pressed = 0;
int main(void) {
//asm volatile ("cpsie i");
initialise_monitor_handles();
//printf("Hello World!\n");
RCC_IOPENR |= 0b1 << 0; // Enable PORTA
GPIOA_MODER &= ~(0b11 << (2*5)); // Clear MODE bits for 5th pin (PA-5)
GPIOA_MODER |= 0b1 << (2*5); // Set MODE bits for 5th pin (PA-5) to 01 (set output)
GPIOC_MODER &= ~(0b11 << (2*13)); // Clear MODE bits for 13th pin (PC-13) (set input)
button_init();
while(1) {
if (g_button_pressed) {
GPIOA_ODR ^= 0b1 << 5;
printf("Button pressed\n");
g_button_pressed = 0;
}
}
}
void button_init() {
RCC_APBENR2 |= 0b1 << 0; // Enable SYSCFGEN
RCC_IOPENR |= 0b1 << 2; // Enable PORTC
EXTI_RTSR1 |= 0b1 << 13; // Enable interrupt on rising edge at EXTI line 13
EXTI_EXTICR4 |= 0x2 << 8; // Set PC-13 as GPIO pin for interrupt
EXTI_IMR1 |= 0x1 << 13; // Unmask EXTI line 13
NVIC_ISER |= 0b1 << 7; // Enable interrupts for EXTI4_15
}
void EXTI4_15_IRQHandler(void) {
g_button_pressed = 1;
printf("Button pressed\n");
EXTI_RPR1 |= 0xFFFF << 0;
}
I'm using the STM32CubeIDE with the default compiler, and and printing via semihosting with OpenOCD.
So, my question is, am I missing a step or doing something wrong?

Answer 1

So, I figured out what my dumb mistake was. I was so focused in trying to understand where I had gone wrong in setting up the external interrupt, I didn't really check if I had set up the button correctly.
I tried to set PC13 as an input:
GPIOC_MODER &= ~(0b11 << (2*13)); // Clear MODE bits for 13th pin (PC-13) (set input)
before I called my button_init() function, which enables the clock for GPIOC via:
RCC_IOPENR |= 0b1 << 2; // Enable PORTC
Since GPIOC was not enabled, PC13 was not set as an input either, so there was nothing to detect.
Here's the fixed code: (I also updated it to use the CMSIS stm32 headers, as suggested by P__J__)
#define STM32G070xx
#include "stm32g0xx.h"
uint8_t volatile g_button_pressed = 0;
void button_init();
//extern void initialise_monitor_handles();
int main(void) {
// initialise_monitor_handles();
//printf("Hello World!\n");
RCC->IOPENR |= 0b1 << 0; // Enable PORTA
GPIOA->MODER &= ~(0b11 << (2*5)); // Clear MODE bits for 5th pin (PA-5)
GPIOA->MODER |= 0b1 << (2*5); // Set MODE bits for 5th pin (PA-5) to 01 (set output)
button_init();
while(1) {
if (g_button_pressed) {
GPIOA->ODR ^= 0b1 << 5;
// printf("Button pressed! Yay!\n");
g_button_pressed = 0;
}
}
}
void button_init() {
// RCC->APBENR2 |= (uint32_t) (0b1 << 0); // Enable SYSCFGEN
RCC->IOPENR |= (uint32_t) (0b1 << 2); // Enable PORTC
GPIOC->MODER &= ~(0b11 << (2*13)); // Clear MODE bits for 13th pin (PC-13) (set input)
EXTI->RTSR1 |= (uint32_t) (0b1 << 13); // Enable interrupt on rising edge at EXTI line 13
EXTI->EXTICR[3] |= (uint32_t) (0x2 << 8); // Set PC-13 as GPIO pin for interrupt
EXTI->IMR1 |= (uint32_t) (0x1 << 13); // Unmask EXTI line 13
NVIC->ISER[0] |= (uint32_t) (0b1 << 7); // Enable interrupts for EXTI4_15
}
void EXTI4_15_IRQHandler(void) {
g_button_pressed = 1;
// printf("Button pressed\n");
EXTI->RPR1 = 0b1 << 13;
}