Danger-alarm/SOFTWARE-FreeRTOS/Common/drivers/Atmel/at91lib/peripherals/tc/tc.c

/* ----------------------------------------------------------------------------
 *         ATMEL Microcontroller Software Support 
 * ----------------------------------------------------------------------------
 * Copyright (c) 2008, Atmel Corporation
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the disclaimer below.
 *
 * Atmel's name may not be used to endorse or promote products derived from
 * this software without specific prior written permission.
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 * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
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 */

//------------------------------------------------------------------------------
//         Headers
//------------------------------------------------------------------------------

#include "tc.h"

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

//------------------------------------------------------------------------------
/// Configures a Timer Counter to operate in the given mode. Timer is stopped
/// after configuration and must be restarted with TC_Start().
/// to obtain the target frequency.
/// \param pTc  Pointer to an AT91S_TC instance.
/// \param mode  Operating mode.
//------------------------------------------------------------------------------
void TC_Configure(AT91S_TC *pTc, unsigned int mode)
{
    // Disable TC clock
    pTc->TC_CCR = AT91C_TC_CLKDIS;

    // Disable interrupts
    pTc->TC_IDR = 0xFFFFFFFF;

    // Clear status register
    pTc->TC_SR;

    // Set mode
    pTc->TC_CMR = mode;
}

//------------------------------------------------------------------------------
/// Starts the timer clock.
/// \param pTc  Pointer to an AT91S_TC instance.
//------------------------------------------------------------------------------
void TC_Start(AT91S_TC *pTc)
{
    pTc->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
}

//------------------------------------------------------------------------------
/// Stops the timer clock.
/// \param pTc  Pointer to an AT91S_TC instance.
//------------------------------------------------------------------------------
void TC_Stop(AT91S_TC *pTc)
{
    pTc->TC_CCR = AT91C_TC_CLKDIS;
}

//------------------------------------------------------------------------------
/// Finds the best MCK divisor given the timer frequency and MCK. The result
/// is guaranteed to satisfy the following equation:
///   (MCK / (DIV * 65536)) <= freq <= (MCK / DIV)
/// with DIV being the highest possible value.
/// Returns 1 if a divisor could be found; otherwise returns 0.
/// \param freq  Desired timer frequency.
/// \param mck  Master clock frequency.
/// \param div  Divisor value.
/// \param tcclks  TCCLKS field value for divisor.
//------------------------------------------------------------------------------
unsigned char TC_FindMckDivisor(
    unsigned int freq,
    unsigned int mck,
    unsigned int *div,
    unsigned int *tcclks)
{
    const unsigned int divisors[5] = {2, 8, 32, 128,
#if defined(at91sam9260) || defined(at91sam9261) || defined(at91sam9263) \
    || defined(at91sam9xe) || defined(at91sam9rl64) || defined(at91cap9)
        BOARD_MCK / 32768};
#else
        1024};
#endif
    unsigned int index = 0;

    // Satisfy lower bound
    while (freq < ((mck / divisors[index]) / 65536)) {

        index++;

        // If no divisor can be found, return 0
        if (index == 5) {

            return 0;
        }
    }

    // Try to maximise DIV while satisfying upper bound
    while (index < 4) {

        if (freq > (mck / divisors[index + 1])) {

            break;
        }
        index++;
    }

    // Store results
    if (div) {

        *div = divisors[index];
    }
    if (tcclks) {

        *tcclks = index;
    }

    return 1;
}