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Arshan Khanifar

Patrick Li (Unlicensed)

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Table of Contents
excludeAt a Glance

Prerequisites

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.

At this point, you should be familiar with the basics of our build system and flashed your first project. You should also be aware of our Git Workflow and Coding Standards.

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Code Block
languagecpp
titlemain.c
// 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)
  GPIOAddressGpioAddress led = {
    .port = GPIO_PORT_B,  //
    .pin = 5,             //
  };
  GPIOSettingsGpioSettings gpio_settings = {
    .direction = GPIO_DIR_OUT,  //
    .state = GPIO_STATE_LOWHIGH,    //
  };
  gpio_init_pin(&led, &gpio_settings);

  // Add infinite loop so we don't exit
  while (true) {
  }

  return 0;
}

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Code Block
languagecpp
titlemain.c
// 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(SoftTimerIDSoftTimerId timer_id, void *context) {
  GPIOAddressGpioAddress *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
  GPIOAddressGpioAddress led = {
    .port = GPIO_PORT_B,  //
    .pin = 5,             //
  };
  GPIOSettingsGpioSettings gpio_settings = {
    .direction = GPIO_DIR_OUT,  //
    .state = GPIO_STATE_LOWHIGH,    //
  };
  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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