FreeRTOS/Demo/CORTEX_M7_SAMV71_Xplained_AtmelStudio/libchip_samv7/source/tc.c

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/** \addtogroup tc_module 
 * The TC driver provides the Interface to configure the Timer Counter (TC).
 *
 *  \section Usage
 * <ul>
 *  <li> Optionally, use TC_FindMckDivisor() to let the program find the best
 *     TCCLKS field value automatically.</li>
 *  <li> Configure a Timer Counter in the desired mode using TC_Configure().</li>
 *  <li> Start or stop the timer clock using TC_Start() and TC_Stop().</li>
 *
 * </ul>
 * For more accurate information, please look at the TC section of the Datasheet.
 *
 * Related files :\n
 * \ref tc.c\n
 * \ref tc.h.\n
*/

 /**
 *  \file
 *
 *  \section Purpose
 *
 *  Interface for configuring and using Timer Counter (TC) peripherals.
 *
 *  \section Usage
 *  -# Optionally, use TC_FindMckDivisor() to let the program find the best
 *     TCCLKS field value automatically.
 *  -# Configure a Timer Counter in the desired mode using TC_Configure().
 *  -# Start or stop the timer clock using TC_Start() and TC_Stop().
 */
 
/**
 * \file
 *
 * Implementation of Timer Counter (TC).
 *
 */

/*------------------------------------------------------------------------------
 *         Headers
 *-----------------------------------------------------------------------------*/

#include "board.h"

#include <assert.h>

/*------------------------------------------------------------------------------
 *         Global functions
 *----------------------------------------------------------------------------*/

/**
 * \brief Configures a Timer Counter Channel
 *
 * Configures a Timer Counter to operate in the given mode. Timer is stopped
 * after configuration and must be restarted with TC_Start(). All the
 * interrupts of the timer are also disabled.
 *
 * \param pTc  Pointer to a Tc instance.
 * \param channel Channel number.
 * \param mode  Operating mode (TC_CMR value).
 */
extern void TC_Configure( Tc *pTc, uint32_t dwChannel, uint32_t dwMode )
{
	TcChannel* pTcCh ;

	assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
	pTcCh = pTc->TC_CHANNEL+dwChannel ;

	/*  Disable TC clock */
	pTcCh->TC_CCR = TC_CCR_CLKDIS ;

	/*  Disable interrupts */
	pTcCh->TC_IDR = 0xFFFFFFFF ;

	/*  Clear status register */
	pTcCh->TC_SR ;

	/*  Set mode */
	pTcCh->TC_CMR = dwMode ;
}

/**
 * \brief Reset and Start the TC Channel
 *
 * Enables the timer clock and performs a software reset to start the counting.
 *
 * \param pTc  Pointer to a Tc instance.
 * \param dwChannel Channel number.
 */
extern void TC_Start( Tc *pTc, uint32_t dwChannel )
{
	TcChannel* pTcCh ;

	assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;

	pTcCh = pTc->TC_CHANNEL+dwChannel ;
	pTcCh->TC_CCR = TC_CCR_CLKEN | TC_CCR_SWTRG ;
}

/**
 * \brief Stop TC Channel
 *
 * Disables the timer clock, stopping the counting.
 *
 * \param pTc     Pointer to a Tc instance.
 * \param dwChannel Channel number.
 */
extern void TC_Stop(Tc *pTc, uint32_t dwChannel )
{
	TcChannel* pTcCh ;

	assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;

	pTcCh = pTc->TC_CHANNEL+dwChannel ;
	pTcCh->TC_CCR = TC_CCR_CLKDIS ;
}

/**
 * \brief Find best MCK divisor
 *
 * Finds the best MCK divisor given the timer frequency and MCK. The result
 * is guaranteed to satisfy the following equation:
 * \code
 *   (MCK / (DIV * 65536)) <= freq <= (MCK / DIV)
 * \endcode
 * with DIV being the highest possible value.
 *
 * \param dwFreq  Desired timer frequency.
 * \param dwMCk  Master clock frequency.
 * \param dwDiv  Divisor value.
 * \param dwTcClks  TCCLKS field value for divisor.
 * \param dwBoardMCK  Board clock frequency.
 *
 * \return 1 if a proper divisor has been found, otherwise 0.
 */
extern uint32_t TC_FindMckDivisor( uint32_t dwFreq, uint32_t dwMCk, 
		uint32_t *dwDiv, uint32_t *dwTcClks, uint32_t dwBoardMCK )
{
	const uint32_t adwDivisors[5] = { 2, 8, 32, 128, BOARD_MCK / 32768 } ;

	uint32_t dwIndex = 0 ;
	dwBoardMCK = dwBoardMCK;
	/*  Satisfy lower bound */
	while ( dwFreq < ((dwMCk / adwDivisors[dwIndex]) / 65536) ) {
		dwIndex++ ;

		/*  If no divisor can be found, return 0 */
		if ( dwIndex == (sizeof( adwDivisors )/sizeof( adwDivisors[0] )) ) {
			return 0 ;
		}
	}

	/*  Try to maximize DIV while satisfying upper bound */
	while ( dwIndex < 4 ) {
		if ( dwFreq > (dwMCk / adwDivisors[dwIndex + 1]) ) {
			break ;
		}
		dwIndex++ ;
	}

	/*  Store results */
	if ( dwDiv ) {
		*dwDiv = adwDivisors[dwIndex] ;
	}
	if ( dwTcClks ) {
		*dwTcClks = dwIndex ;
	}
	return 1 ;
}