Add gpio.{h, c}

src/gpio.c

@@ -0,0 +1,16 @@
+#include <inttypes.h>
+#include <stdbool.h>
+
+#include "gpio.h"
+
+void gpio_set_mode(uint16_t pin, GPIO_MODE mode) {
+  struct gpio *gpio = GPIO(PINPORT(pin));     // GPIO port address
+  int pn = PINNUM(pin);                       // Pin number
+  gpio->MODER &= ~(0x0011 << (pn * 2));       // Clear existing setting. Each pin uses 2 bits
+  gpio->MODER |= (mode & 0b011) << (pn * 2);  // Set new mode. Each pin uses 2 bits
+}
+
+void gpio_write(uint16_t pin, bool val) {
+  struct gpio *gpio = GPIO(PINPORT(pin));
+  gpio->BSRR = (0b0011 << PINNUM(pin)) << (val ? 0 : 16);
+}