Bo mạch GPIO 2D

/* Đèn chạy 4 LED (GPIO17, 27, 22, 23), nút SW1 (GPIO26) đổi chiều.
 * Ghi thẳng thanh ghi GPIO như trên Pi thật qua /dev/gpiomem.
 */
#include <stdbool.h>
#include <stdint.h>
 
/* Chỉ số thanh ghi (word) tính từ gpio_base */
#define GPFSEL_IDX(pin)  ((pin) / 10U)
#define GPSET0_IDX       (7U)
#define GPCLR0_IDX       (10U)
#define GPLEV0_IDX       (13U)
 
#define FSEL_MASK        (7U)
#define FSEL_OUTPUT      (1U)
#define LED_COUNT        (4U)
#define BTN_PIN          (26U)
#define STEP_MS          (150U)
 
static const uint32_t led_pins[LED_COUNT] = {17U, 27U, 22U, 23U};
 
static void gpio_set_output(uint32_t pin)
{
    uint32_t shift = (pin % 10U) * 3U;
    uint32_t reg = gpio_base[GPFSEL_IDX(pin)];
 
    reg &= ~(FSEL_MASK << shift);
    reg |= (FSEL_OUTPUT << shift);
    gpio_base[GPFSEL_IDX(pin)] = reg;
}
 
static bool is_button_pressed(void)
{
    return (gpio_base[GPLEV0_IDX] & (1U << BTN_PIN)) == 0U;
}
 
int main(void)
{
    uint32_t i;
    uint32_t pos = 0U;
    uint32_t all_mask = 0U;
    bool is_forward = true;
    bool was_pressed = false;
 
    for (i = 0U; i < LED_COUNT; i++) {
        gpio_set_output(led_pins[i]);
        all_mask |= (1U << led_pins[i]);
    }
 
    while (true) {
        bool pressed = is_button_pressed();
 
        if (pressed && !was_pressed) {
            is_forward = !is_forward;
        }
        was_pressed = pressed;
 
        gpio_base[GPCLR0_IDX] = all_mask;
        gpio_base[GPSET0_IDX] = (1U << led_pins[pos]);
 
        if (is_forward) {
            pos = (pos + 1U) % LED_COUNT;
        } else {
            pos = (pos + LED_COUNT - 1U) % LED_COUNT;
        }
        delay_ms(STEP_MS);
    }
}