text: /* mbed Microcontroller Library
   * Copyright (c) 2006-2013 ARM Limited
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  #include "mbed_assert.h"
  #include "gpio_api.h"
  #include "pinmap.h"
  
  uint32_t gpio_set(PinName pin) {
      MBED_ASSERT(pin != (PinName)NC);
      uint32_t port_index = (uint32_t) pin >> 4;
  
      // Enable GPIO peripheral clock
      RCC->AHB1ENR |= 1 << port_index;
  
      pin_function(pin, STM_PIN_DATA(0, 0));
      return 1 << ((uint32_t) pin & 0xF);
  }
  
  void gpio_init(gpio_t *obj, PinName pin) {
      obj->pin = pin;
      if (pin == (PinName)NC)
          return;
  
      obj->mask = gpio_set(pin);
  
      uint32_t port_index = (uint32_t) pin >> 4;
      
      GPIO_TypeDef *port_reg = (GPIO_TypeDef *) (GPIOA_BASE + (port_index << 10));
      obj->reg_mode = &port_reg->MODER;
      obj->reg_set = &port_reg->BSRRL;
      obj->reg_clr = &port_reg->BSRRH;
      obj->reg_in  = &port_reg->IDR;
  }
  
  void gpio_mode(gpio_t *obj, PinMode mode) {
      pin_mode(obj->pin, mode);
  }
  
  void gpio_dir(gpio_t *obj, PinDirection direction) {
      MBED_ASSERT(obj->pin != (PinName)NC);
      switch (direction) {
          case PIN_INPUT :
              pin_function(obj->pin, STM_PIN_DATA(0, 0));
              break;
          case PIN_OUTPUT:
              pin_function(obj->pin, STM_PIN_DATA(1, 0));
              break;
      }
  }
  