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Prerequisites
- Same as Module 2
Blinking LED
Now, let's modify the getting_started project to toggle an LED once a second. First, we'll use our Hardware Abstraction Library (HAL). As a refresher, the key purpose of a HAL is to abstract platform details into a common, portable API to allow developers to write high-level application code independently of the underlying hardware.
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// Turns the LED on and sits forever
#include <stdbool.h>
#include "gpio.h"
#include "log.h"
int main(void) {
LOG_DEBUG("Hello World!\n");
// Init GPIO module
gpio_init();
// Set up PC9 as an output, default to output 0 (GND)
GPIOAddress led = {
.port = GPIO_PORT_CB, //
.pin = 95, //
};
GPIOSettings gpio_settings = {
.direction = GPIO_DIR_OUT, //
.state = GPIO_STATE_LOW, //
};
gpio_init_pin(&led, &gpio_settings);
// Add infinite loop so we don't exit
while (true) {
}
return 0;
} |
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# Just make we're following the style guide :) make format make lint # Build and flash to the DiscoveryController boardBoard make program PROJECT=getting_started PROBE=stlink-v2 |
Great! You should see a solid LED on the Discovery boardController Board. This is pretty simple.
Blinking an LED - HAL
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// Blink an LED
#include <stdbool.h>
#include "gpio.h"
#include "interrupt.h"
#include "log.h"
#include "soft_timer.h"
#include "wait.h"
#define BLINK_LED_TIMEOUT_SECS 1
// Timeout callback
static void prv_blink_timeout(SoftTimerID timer_id, void *context) {
GPIOAddress *led = context;
gpio_toggle_state(led);
LOG_DEBUG("Toggling LED\n");
// Schedule another timer - this creates a periodic timer
soft_timer_start_seconds(BLINK_LED_TIMEOUT_SECS, prv_blink_timeout, led, NULL);
}
int main(void) {
LOG_DEBUG("Hello World!\n");
// Initialize our modules
gpio_init();
interrupt_init();
soft_timer_init();
// Set up the pin
GPIOAddress led = {
.port = GPIO_PORT_CB, //
.pin = 95, //
};
GPIOSettings gpio_settings = {
.direction = GPIO_DIR_OUT, //
.state = GPIO_STATE_LOW, //
};
gpio_init_pin(&led, &gpio_settings);
// Begin a timer
soft_timer_start_seconds(BLINK_LED_TIMEOUT_SECS, prv_blink_timeout, &led, NULL);
// Infinite loop
while (true) {
// Wait for interrupts
wait();
}
return 0;
} |
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