usart_driver.c

/* This file has been prepared for Doxygen automatic documentation generation.*/
/*! \file *********************************************************************
 *
 * \brief
 *      XMEGA USART driver source file.
 *
 *      This file contains the function implementations the XMEGA interrupt
 *      and polled USART driver.
 *
 *      The driver is not intended for size and/or speed critical code, since
 *      most functions are just a few lines of code, and the function call
 *      overhead would decrease code performance. The driver is intended for
 *      rapid prototyping and documentation purposes for getting started with
 *      the XMEGA ADC module.
 *
 *      For size and/or speed critical code, it is recommended to copy the
 *      function contents directly into your application instead of making
 *      a function call.
 *
 *      Some functions use the following construct:
 *          "some_register = ... | (some_parameter ? SOME_BIT_bm : 0) | ..."
 *      Although the use of the ternary operator ( if ? then : else ) is discouraged,
 *      in some occasions the operator makes it possible to write pretty clean and
 *      neat code. In this driver, the construct is used to set or not set a
 *      configuration bit based on a boolean input parameter, such as
 *      the "some_parameter" in the example above.
 *
 */

#include "usart_driver.h"



/*! \brief Initializes buffer and selects what USART module to use.
 *
 *  Initializes receive and transmit buffer and selects what USART module to use,
 *  and stores the data register empty interrupt level.
 *
 *  \param usart_data           The USART_data_t struct instance.
 *  \param usart                The USART module.
 *  \param dreIntLevel          Data register empty interrupt level.
 */
void USART_InterruptDriver_Initialize(USART_data_t * usart_data,
                                      USART_t * usart,
                                      USART_DREINTLVL_t dreIntLevel)
{
	usart_data->usart = usart;
	usart_data->dreIntLevel = dreIntLevel;

	usart_data->buffer.RX_Tail = 0;
	usart_data->buffer.RX_Head = 0;
	usart_data->buffer.TX_Tail = 0;
	usart_data->buffer.TX_Head = 0;
}


/*! \brief Set USART DRE interrupt level.
 *
 *  Set the interrupt level on Data Register interrupt.
 *
 *  \note Changing the DRE interrupt level in the interrupt driver while it is
 *        running will not change the DRE interrupt level in the USART before the
 *        DRE interrupt have been disabled and enabled again.
 *
 *  \param usart_data         The USART_data_t struct instance
 *  \param dreIntLevel        Interrupt level of the DRE interrupt.
 */
void USART_InterruptDriver_DreInterruptLevel_Set(USART_data_t * usart_data,
                                                 USART_DREINTLVL_t dreIntLevel)
{
	usart_data->dreIntLevel = dreIntLevel;
}


/*! \brief Test if there is data in the transmitter software buffer.
 *
 *  This function can be used to test if there is free space in the transmitter
 *  software buffer.
 *
 *  \param usart_data The USART_data_t struct instance.
 *
 *  \retval true      There is data in the receive buffer.
 *  \retval false     The receive buffer is empty.
 */
bool USART_TXBuffer_FreeSpace(USART_data_t * usart_data)
{
	/* Make copies to make sure that volatile access is specified. */
	uint8_t tempHead = (usart_data->buffer.TX_Head + 1) & USART_TX_BUFFER_MASK;
	uint8_t tempTail = usart_data->buffer.TX_Tail;

	/* There are data left in the buffer unless Head and Tail are equal. */
	return (tempHead != tempTail);
}



/*! \brief Put data (5-8 bit character).
 *
 *  Stores data byte in TX software buffer and enables DRE interrupt if there
 *  is free space in the TX software buffer.
 *
 *  \param usart_data The USART_data_t struct instance.
 *  \param data       The data to send.
 */
bool USART_TXBuffer_PutByte(USART_data_t * usart_data, uint8_t data)
{
	uint8_t tempCTRLA;
	uint8_t tempTX_Head;
	bool TXBuffer_FreeSpace;
	USART_Buffer_t * TXbufPtr;

	TXbufPtr = &usart_data->buffer;
	TXBuffer_FreeSpace = USART_TXBuffer_FreeSpace(usart_data);


	if(TXBuffer_FreeSpace)
	{
	  	tempTX_Head = TXbufPtr->TX_Head;
	  	TXbufPtr->TX[tempTX_Head]= data;
		/* Advance buffer head. */
		TXbufPtr->TX_Head = (tempTX_Head + 1) & USART_TX_BUFFER_MASK;

		/* Enable DRE interrupt. */
		tempCTRLA = usart_data->usart->CTRLA;
		tempCTRLA = (tempCTRLA & ~USART_DREINTLVL_gm) | usart_data->dreIntLevel;
		usart_data->usart->CTRLA = tempCTRLA;
	}
	return TXBuffer_FreeSpace;
}



/*! \brief Test if there is data in the receive software buffer.
 *
 *  This function can be used to test if there is data in the receive software
 *  buffer.
 *
 *  \param usart_data         The USART_data_t struct instance
 *
 *  \retval true      There is data in the receive buffer.
 *  \retval false     The receive buffer is empty.
 */
bool USART_RXBufferData_Available(USART_data_t * usart_data)
{
	/* Make copies to make sure that volatile access is specified. */
	uint8_t tempHead = usart_data->buffer.RX_Head;
	uint8_t tempTail = usart_data->buffer.RX_Tail;

	/* There are data left in the buffer unless Head and Tail are equal. */
	return (tempHead != tempTail);
}



/*! \brief Get received data (5-8 bit character).
 *
 *  The function USART_RXBufferData_Available should be used before this
 *  function is used to ensure that data is available.
 *
 *  Returns data from RX software buffer.
 *
 *  \param usart_data       The USART_data_t struct instance.
 *
 *  \return         Received data.
 */
uint8_t USART_RXBuffer_GetByte(USART_data_t * usart_data)
{
	USART_Buffer_t * bufPtr;
	uint8_t ans;

	bufPtr = &usart_data->buffer;
	ans = (bufPtr->RX[bufPtr->RX_Tail]);

	/* Advance buffer tail. */
	bufPtr->RX_Tail = (bufPtr->RX_Tail + 1) & USART_RX_BUFFER_MASK;

	return ans;
}



/*! \brief RX Complete Interrupt Service Routine.
 *
 *  RX Complete Interrupt Service Routine.
 *  Stores received data in RX software buffer.
 *
 *  \param usart_data      The USART_data_t struct instance.
 */
bool USART_RXComplete(USART_data_t * usart_data)
{
	USART_Buffer_t * bufPtr;
	bool ans;

	bufPtr = &usart_data->buffer;
	/* Advance buffer head. */
	uint8_t tempRX_Head = (bufPtr->RX_Head + 1) & USART_RX_BUFFER_MASK;

	/* Check for overflow. */
	uint8_t tempRX_Tail = bufPtr->RX_Tail;
	uint8_t data = usart_data->usart->DATA;

	if (tempRX_Head == tempRX_Tail) {
	  	ans = false;
	}else{
		ans = true;
		usart_data->buffer.RX[usart_data->buffer.RX_Head] = data;
		usart_data->buffer.RX_Head = tempRX_Head;
	}
	return ans;
}



/*! \brief Data Register Empty Interrupt Service Routine.
 *
 *  Data Register Empty Interrupt Service Routine.
 *  Transmits one byte from TX software buffer. Disables DRE interrupt if buffer
 *  is empty. Argument is pointer to USART (USART_data_t).
 *
 *  \param usart_data      The USART_data_t struct instance.
 */
void USART_DataRegEmpty(USART_data_t * usart_data)
{
	USART_Buffer_t * bufPtr;
	bufPtr = &usart_data->buffer;

	/* Check if all data is transmitted. */
	uint8_t tempTX_Tail = usart_data->buffer.TX_Tail;
	if (bufPtr->TX_Head == tempTX_Tail){
	    /* Disable DRE interrupts. */
		uint8_t tempCTRLA = usart_data->usart->CTRLA;
		tempCTRLA = (tempCTRLA & ~USART_DREINTLVL_gm) | USART_DREINTLVL_OFF_gc;
		usart_data->usart->CTRLA = tempCTRLA;

	}else{
		/* Start transmitting. */
		uint8_t data = bufPtr->TX[usart_data->buffer.TX_Tail];
		usart_data->usart->DATA = data;

		/* Advance buffer tail. */
		bufPtr->TX_Tail = (bufPtr->TX_Tail + 1) & USART_TX_BUFFER_MASK;
	}
}


/*! \brief Put data (9 bit character).
 *
 *  Use the function USART_IsTXDataRegisterEmpty before using this function to
 *  put 9 bit character to the TX register.
 *
 *  \param usart      The USART module.
 *  \param data       The data to send.
 */
void USART_NineBits_PutChar(USART_t * usart, uint16_t data)
{
	if(data & 0x0100) {
		usart->CTRLB |= USART_TXB8_bm;
	}else {
		usart->CTRLB &= ~USART_TXB8_bm;
	}

	usart->DATA = (data & 0x00FF);
}


/*! \brief Get received data (9 bit character).
 *
 *  This function reads out the received 9 bit character (uint16_t).
 *  Use the function USART_IsRXComplete to check if anything is received.
 *
 *  \param usart      The USART module.
 *
 *  \retval           Received data.
 */
uint16_t USART_NineBits_GetChar(USART_t * usart)
{
	if(usart->CTRLB & USART_RXB8_bm) {
		return(0x0100 | usart->DATA);
	}else {
		return(usart->DATA);
	}
}