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stm32-better-blink/main.c

98 lines
2.8 KiB
C

/*
* My first project
*
* It blinks LEDs like counting in binary, when the button is pressed, it reverses the order
*
* Build on top of libopenocm3, blackbox parts of code (setup()) copied from
* libopencm3-examples/examples/stm32/f1/stm32vl-discovery/button project
*
* Open source licence, let's say Artistic Licence, although it doesn't matter, as it is local only
*/
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/f1/exti.h>
#include <libopencm3/stm32/f1/nvic.h>
#include <stdbool.h>
//#define DELAY 8000000 // Should be a second, or maybe not (second iff 8MHz clk, 1/3second if 24MHz clk) // Too long!!
#define DELAY 4000000 // This is bad -- it's a value that was found to be OK
#define STM32F1 1 // Needed for libopencm3
volatile enum {FORWARD, BACKWARD} direction;
volatile bool running = false;
void setup (void) { // All the blackbox code
// Set up clock
rcc_clock_setup_in_hse_8mhz_out_24mhz();
// Enable the two GPIOs
rcc_periph_clock_enable(RCC_GPIOC);
rcc_periph_clock_enable(RCC_GPIOA);
// Enable AFIO (we need that to map GPIO to EXTI)
rcc_periph_clock_enable(RCC_AFIO);
// Enable EXTI0 interrupt.
// The interrupts are a bit magic, as the Internet says (the datasheet for F100RBT6B does not mention the EXTI/NVIC interface)
// This one is for EXTI0 ~~ GPIOx0 pins
nvic_enable_irq(NVIC_EXTI0_IRQ);
// GPIO C8 amd C9 are the two LEDs
gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO8 | GPIO9);
// GPIO A0 is the push button
// And we set it as a regular button and enable its interrupts in the next block
gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO0);
// Configure the EXTI0 interrupts
// 1. Which pin
exti_select_source(EXTI0, GPIOA);
// 2. Which edge
exti_set_trigger(EXTI0, EXTI_TRIGGER_RISING);
// 3. Enable the interrupts
exti_enable_request(EXTI0);
}
// libopencm3 has a pre-declared interrupt handlers, so it needs to have this name
void exti0_isr (void) {
// Clear the interrupt
exti_reset_request(EXTI0);
// NB: For some reason it is at the begining in the examples
// It needs to be here (possibly because of reordering, when this was at the end, I usually got the interrupt twice).
if (!running) {
direction = FORWARD;
} else {
direction = direction == FORWARD ? BACKWARD : FORWARD;
}
running = true;
}
int main (void) {
setup();
// Array of what leds should be on
uint16_t states[4] = {0, GPIO9, GPIO8, GPIO9 | GPIO8};
char state = 0;
int i;
// Initial wait
while (!running) ;
while (true) {
for (i=0 ; i<DELAY ; i++) {
__asm ("nop");
}
state = (direction == FORWARD ? (state + 1)%4 : (/*state+4-1*/ state+3)%4 ); // New state
gpio_set(GPIOC, states[state]);
gpio_clear(GPIOC, (GPIO8 | GPIO9) ^ states[state]);
}
return 0;
}