====== Lab05 - Hardware initialization ======
This exercise deals with NUCLEO I/O initialization of the User LED and User Button. The exercise also deals with usage of these resources. The definition of the LED and Button connection is described in the board [[http://www.st.com/resource/en/user_manual/dm00105823.pdf|user manual]].

Task:
  * Find the CPU pin and port for the User LED (green) output control.
  * Find the CPU pin and port for the User Button input control.

==== LED ====
The NUCLEO board contains a green LED controlled by the CPU. The LED is connected to the CPU pin XX of the port GPIOXX. The output needs to be initialized through the GPIO_Init function as depicted below. The initialization should be placed into void GPIO_Configuration( void ) function of the project.

<code>
  // PXX = USER LED
  GPIO_InitStructure.GPIO_Pin         = GPIO_Pin_XX;
  GPIO_InitStructure.GPIO_Mode        = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_OType       = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_Speed       = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_PuPd        = GPIO_PuPd_UP;
  GPIO_Init( GPIOXX, &GPIO_InitStructure );
</code>

==== Button ====
The user button is hardwired to a different port then LED and USART. This means the respective GPIO needs to be initialized and connected to the clock source. This operation should be done in void RCC_Configuration( void ) function: see below.

<code>
  // GPIOC clock enable
  RCC_AHB1PeriphClockCmd( RCC_AHB1Periph_GPIOC, ENABLE );
</code>

The initialization of the input pin is performed in the same way as the output pin with small difference: GPIO_Mode_IN.

<code>
  // PXX = USER Button
  GPIO_InitStructure.GPIO_Pin         = GPIO_Pin_XX;
  GPIO_InitStructure.GPIO_Mode        = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_OType       = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_Speed       = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_PuPd        = GPIO_PuPd_UP;
  GPIO_Init( GPIOXX, &GPIO_InitStructure );
</code>

==== Main function ====
The setting of the output can be done through GPIO_SetBits and GPIO_ResetBits (or GPIO_ToggleBits). The input can be read through GPIO_ReadInputDataBit. The list of functions available for input output manipulation is described in stm32f4xx_gpio.h.

<code>
int main(void)
{
	// Init
	RCC_Configuration();

	GPIO_Configuration();

	USART2_Configuration();


	// Process
	OutString("Welcome to Nucleo F401RE\r\n");

	while(1) // Don't want to exit
	{
		uint16_t Data;
		uint8_t btData;

		while(USART_GetFlagStatus(USART2, USART_FLAG_RXNE) == RESET); // Wait for Char

		Data = USART_ReceiveData(USART2); // Collect Char

		OutString("Welcome to Nucleo F401RE\r\n");
		USART_SendData(USART2, Data); // Echo Char
		OutString("\n");

		GPIO_ToggleBits( GPIOA, GPIO_Pin_5 );

		btData = GPIO_ReadInputDataBit( GPIOC, GPIO_Pin_13 );
		if( !btData )
		{
			OutString("Butt press\r\n");
		}
	} // END while(1)

} // END main
</code>

==== Exercise ====
  * Use the initialization of the HW components and provide interface which allows you to read/write the state to the inputs/outputs.
  * Adjust the program developed in HomeWork 01 to be able to:
     * Read the state of the button.
     * Write the state of the User LED.