Add nrf52 gpio driver abstraction

src/platform/nrf52/gpio.c

@@ -0,0 +1,63 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stddef.h>
+
+#include "gpio.h"
+
+#include "nrf_gpio.h"
+
+int gpio_open(const struct driver *drv)
+{
+    assert(NULL != drv);
+
+    struct gpio *this = (struct gpio *)(drv->dev);
+
+    if(this->dir == OUT) {
+        nrf_gpio_cfg_output((uint32_t)(this->pin));
+    nrf_gpio_pin_clear(this->pin);
+    }
+    // FIXME: implement input configuration
+
+    return 0;
+}
+
+int gpio_close(const struct driver *drv)
+{
+    assert(NULL != drv);
+
+    struct gpio *this = (struct gpio *)(drv->dev);
+    nrf_gpio_pin_clear(this->pin);
+
+    return 0;
+}
+
+int gpio_read(const struct driver *drv, char *buffer, unsigned int len)
+{
+    assert(NULL != drv);
+
+    if(len == 0) {
+        return 0;
+    }
+
+    struct gpio *this = (struct gpio *)(drv->dev);
+
+    uint32_t value = nrf_gpio_pin_read(this->pin);
+    buffer[0] = value + 0x30;   // ascii convert
+
+    return 1;
+}
+
+int gpio_write(const struct driver *drv, const char *buffer, unsigned int len)
+{
+    assert((NULL != drv) && (NULL != buffer));
+
+    if(len == 0) {
+        return 0;
+    }
+
+    struct gpio *this = (struct gpio *)(drv->dev);
+
+    nrf_gpio_pin_write(this->pin, buffer[0] - 0x30);
+
+    return 1;
+}