mutex example

mutex-test.c

#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/cm3/nvic.h>
#include <libopencm3/cm3/systick.h>
#include <libopencm3/cm3/sync.h>

#include <local_libs/util_timer.h>

#include <local_conf/board_conf.h>

static mutex_t mtx;
static uint32_t systick_busy_cnt = 0;
static uint32_t systick_busy_total = 0;

static void clock_setup(void)
{
	/* Run at 72MHz */
	rcc_clock_setup_in_board_out_72mhz();
}

static void gpio_setup(void)
{
	/* Enable LED GPIO clock. */
	rcc_periph_clock_enable(RCC_GPIOB);
	rcc_periph_clock_enable(RCC_GPIOA);

	/* Set LED GPIO to 'output push-pull'. */
	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ,
		      GPIO_CNF_OUTPUT_PUSHPULL, GPIO11);

	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
		      GPIO_CNF_OUTPUT_PUSHPULL, GPIO2);
	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
		      GPIO_CNF_OUTPUT_PUSHPULL, GPIO3);
}

/*
 * Set up the systick system periodic interrupt
 */
static void systick_setup(void)
{
	/* 72MHz / 8 => 9000000 counts per second. */
	systick_set_clocksource(STK_CSR_CLKSOURCE_AHB_DIV8);

	/* 9000000/9000 = 1000 overflows per second - every 1ms one interrupt */
	/* SysTick interrupt every N clock pulses: set reload to N-1 */
	systick_set_reload(8999);

	systick_interrupt_enable();

	/* Start counting. */
	systick_counter_enable();
}

/*
 * Called at 1kHz
 */
void sys_tick_handler(void)
{
	int i;

	if (mutex_trylock(&mtx))
	{
		gpio_toggle(GPIOA,GPIO3);
		mutex_unlock(&mtx);
	}
}

int main(void)
{
	clock_setup();
	gpio_setup();

	util_timer_t tim_ms;
	tim_ms.periph = DELAY_TIM;
	tim_ms.res = RES_MS;
	timer_init(&tim_ms);

	systick_setup();

	while (1)
	{
		mutex_lock(&mtx);
		gpio_set(GPIOB,GPIO11);
		gpio_set(GPIOA,GPIO2);
		timer_delay(&tim_ms,20); // wait 20 ms with timer
		gpio_clear(GPIOB,GPIO11);
		gpio_clear(GPIOA,GPIO2);
		mutex_unlock(&mtx);
		timer_delay(&tim_ms,80); // wait 80 ms with timer
	}

	return 0;
}