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);
+}

src/gpio.h

@@ -0,0 +1,42 @@
+#ifndef GPIO_H_
+#define GPIO_H_
+
+#include <stdbool.h>
+#include <inttypes.h>
+
+struct gpio {
+  volatile uint32_t MODER;    // Port mode register
+  volatile uint32_t OTYPER;   // Port output type register
+  volatile uint32_t OSPEEDR;  // Port output speed register
+  volatile uint32_t PUPDR;    // Port pull-up/pull-down register
+  volatile uint32_t IDR;      // Port input data register
+  volatile uint32_t ODR;      // Port output data register
+  volatile uint32_t BSRR;     // Port bit set/reset register
+  volatile uint32_t LCKR;     // Port configuration lock register
+  volatile uint32_t AFRL[2];  // Alternative function low register
+  volatile uint32_t AFRH[2];  // Alternative function high register
+};
+
+#define GPIO_BASE_ADDR (0x40020000U)
+#define GPIO_PORT_OFFSET (0x400U)
+#define GPIO(port) ((struct gpio*)(uintptr_t)(GPIO_BASE_ADDR + (GPIO_PORT_OFFSET * port)))
+
+#define BIT(x) (1 << x)
+// Create a 16bit number from a port and pin
+#define PIN(port, num) ((((port) - 'A') << 8) | num)
+// get the lower byte from a PIN
+#define PINNUM(pin) (pin & 0b1111)
+// get the upper byte from a PIN
+#define PINPORT(pin) (pin >> 8)
+
+typedef enum {
+  GPIO_MODE_INPUT,
+  GPIO_MODE_OUTPUT,
+  GPIO_MODE_AF,
+  GPIO_MODE_ANALOG
+} GPIO_MODE;
+
+void gpio_set_mode(uint16_t pin, GPIO_MODE mode);
+void gpio_write(uint16_t pin, bool val);
+
+#endif