Subversion Repositories idreammicro-avr

/**************************************************************************//**

 * \brief TWI library

 * \author Copyright (C) 2009  Julien Le Sech - www.idreammicro.com

 * \version 1.0

 * \date 20090501

 *

 * This file is part of the iDreamMicro library.

 *

 * This library is free software: you can redistribute it and/or modify it under

 * the terms of the GNU Lesser General Public License as published by the Free

 * Software Foundation, either version 3 of the License, or (at your option) any

 * later version.

 *

 * This library is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more

 * details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program. If not, see http://www.gnu.org/licenses/

 ******************************************************************************/

/**************************************************************************//**

 * \file twi.c

 ******************************************************************************/

/******************************************************************************

 * Header file inclusions.

 ******************************************************************************/

#include <twi/twi.h>

#include <useful/bits.h>

#include <avr/io.h>

#include <util/twi.h>

#include <assert.h>

#include <stdint.h>

#include <stdlib.h>

/******************************************************************************

 * Private macros.

 ******************************************************************************/

/**************************************************************************//**

 * \def     TWI__MAX_FREQUENCY

 * \brief   Max frequency of TWI bus.

 ******************************************************************************/

#define TWI__MAX_FREQUENCY  400000

/******************************************************************************

 * Private types.

 ******************************************************************************/

/**************************************************************************//**

 * \enum    twi__prescaler_values

 * \brief   Available TWI bus prescaler values.

 *

 * \typedef twi__prescaler_value_t

 * \brief   TWI bus prescaler value.

 ******************************************************************************/

typedef enum twi__prescaler_values

{

    TWI__PRESCALER_VALUE__1,

    TWI__PRESCALER_VALUE__4,

    TWI__PRESCALER_VALUE__16,

    TWI__PRESCALER_VALUE__64,

    TWI__PRESCALER_VALUE__INVALID

} twi__prescaler_value_t;

/**************************************************************************//**

 * \struct  twi__prescaler_configuration

 * \brief   TWI bus prescaler configuration.

 *

 * \typedef twi__prescaler_configuration_t

 * \brief   TWI bus prescaler configuration.

 ******************************************************************************/

typedef struct twi__prescaler_configuration

{

    uint8_t value;

    uint8_t bits;

} twi__prescaler_configuration_t;

/******************************************************************************

 * Private constant definitions.

 ******************************************************************************/

/**************************************************************************//**

 * \var     prescaler_configurations

 * \brief   Available prescaler configurations.

 ******************************************************************************/

static const twi__prescaler_configuration_t prescaler_configurations[] =

{

    [TWI__PRESCALER_VALUE__1] =

    {

        .value  = 1,

        .bits   = 0

    },

    [TWI__PRESCALER_VALUE__4] =

    {

        .value  = 4,

        .bits   = _BV(TWPS0)

    },

    [TWI__PRESCALER_VALUE__16] =

    {

        .value  = 16,

        .bits   = _BV(TWPS1)

    },

    [TWI__PRESCALER_VALUE__64] =

    {

        .value  = 64,

        .bits   = _BV(TWPS1) | _BV(TWPS0)

    }

};

/******************************************************************************

 * Private function prototypes.

 ******************************************************************************/

/**************************************************************************//**

 * \fn static inline uint8_t twi__compute_bit_rate(

 * uint32_t f_scl,

 * uint8_t  prescaler_value)

 *

 * \brief

 *

 * \param   f_scl           SCL frequency.

 * \param   prescaler_value Prescaler value.

 ******************************************************************************/

static inline

uint8_t

twi__compute_bit_rate

(

    uint32_t    f_scl,

    uint8_t     prescaler_value

);

/******************************************************************************

 * Public function definitions.

 ******************************************************************************/

/**************************************************************************//**

 * \fn void twi__initialize(uint32_t frequency)

 *

 * \brief Initialize TWI.

 *

 * \param   frequency   TWI frequency (up to 400 kHz).

 ******************************************************************************/

void twi__initialize

(

    uint32_t frequency

){

    // Check the preconditions.

    assert(TWI__MAX_FREQUENCY >= frequency);

    uint16_t bit_rate = UINT16_MAX;

    twi__prescaler_value_t prescaler_value = TWI__PRESCALER_VALUE__1;

    // Compute bit rate and prescaler value.

    do

    {

        bit_rate = twi__compute_bit_rate

        (

            frequency,

            prescaler_configurations[prescaler_value].value

        );

    } while (UINT8_MAX < bit_rate && TWI__PRESCALER_VALUE__INVALID > prescaler_value++);

    // Set bit rate.

    TWBR = bit_rate;

    // Set prescaler value.

    TWSR = prescaler_configurations[prescaler_value].bits;

}

/**************************************************************************//**

 * \fn twi__error_t twi__start(void)

 *

 * \brief

 ******************************************************************************/

twi__error_t

twi__start

(

    void

){

    // Send start condition.

    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);

    // Wait for TWINT flag set. This indicates that the START condition has

    // been transmitted.

    while (!(TWCR & (1 << TWINT)));

    // Check value of TWI Status Register. Mask prescaler bits.

    if (TWSR & TW_NO_INFO != TW_START)

    {

        // If status is different from START (TW_START), return error.

        return TWI__ERROR__ERROR;

    }

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn twi__error_t twi__repeat_start(void)

 *

 * \brief

 ******************************************************************************/

twi__error_t

twi__repeat_start

(

    void

){

    // TODO: check if TWSTO must be set.

    // Send start condition.

    TWCR = (1 << TWEN) | (1 << TWINT) | (1 << TWSTA) | (1 << TWSTO);

    // Wait for TWINT flag set. This indicates that the START condition has

    // been transmitted.

    while (!(TWCR & (1 << TWINT)));

    // Check value of TWI Status Register. Mask prescaler bits.

    if (TWSR & TW_NO_INFO != TW_REP_START)

    {

        //  If status different from START (TW_REP_START), return error.

        return TWI__ERROR__ERROR;

    }

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn twi__error_t twi__send_slar(uint8_t sla)

 *

 * \brief

 *

 * \param   sla

 ******************************************************************************/

twi__error_t

twi__send_slar

(

    uint8_t sla

){

    // Load SLA into TWDR register.

    TWDR = sla | TW_READ;

    // Clear TWINT bit in TWCR to start transmission of address.

    TWCR = (1 << TWINT) | (1 << TWEN);

    // Wait for TWINT flag set. This indicates that the SLA+W (TW_WRITE) has

    // been transmitted, and ACK/NACK has been received.

    while (!(TWCR & (1 << TWINT)));

    // Check value of TWI Status Register. Mask prescaler bits. If status

    // different from MT_SLA_ACK (TW_MR_SLA_ACK), return error.

    if (TWSR & TW_NO_INFO != TW_MR_SLA_ACK)

    {

        return TWI__ERROR__ERROR;

    }

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn twi__error_t twi__send_slaw(uint8_t sla)

 *

 * \brief

 *

 * \param   sla

 ******************************************************************************/

twi__error_t

twi__send_slaw

(

    uint8_t sla

){

    // Load SLA into TWDR register.

    TWDR = sla | TW_WRITE;

    // Clear TWINT bit in TWCR to start transmission of address.

    TWCR = (1 << TWINT) | (1 << TWEN);

    // Wait for TWINT flag set. This indicates that the SLA+W (TW_WRITE) has

    // been transmitted, and ACK/NACK has been received.

    while (!(TWCR & (1 << TWINT)));

    // Check value of TWI Status Register. Mask prescaler bits. If status

    // different from MT_SLA_ACK (TW_MT_SLA_ACK), return error.

    if (TWSR & TW_NO_INFO != TW_MT_SLA_ACK)

    {

        return TWI__ERROR__ERROR;

    }

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn twi__error_t twi__send_data(uint8_t data)

 *

 * \brief

 *

 * \param   data    Data to send.

 ******************************************************************************/

twi__error_t

twi__send_data

(

    uint8_t data

){

    // Load data into TWDR register.

    TWDR = data;

    // Clear TWINT bit in TWCR to start transmission of data.

    TWCR = (1 << TWINT) | (1 << TWEN);

    // Wait for TWINT flag set. This indicates that the data has been

    // transmitted, and ACK/NACK has been receiver.

    while (!(TWCR & (1 << TWINT)));

    // Check value of TWI status register. Mask prescaler bits. If status

    // different from MT_DATA_ACK (TW_MT_DATA_ACK), return error.

    if (TWSR & TW_NO_INFO != TW_MT_DATA_ACK)

    {

        return TWI__ERROR__ERROR;

    }

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn twi__error_t twi__receive_data_ack(uint8_t* p_data)

 *

 * \brief

 *

 * \param   p_data

 ******************************************************************************/

twi__error_t

twi__receive_data_ack

(

    uint8_t* p_data

){

    // Check the preconditions.

    assert(NULL != p_data);

    TWCR = (1 << TWEN) | (1 << TWINT) | (1 << TWEA);

    while (!(TWCR & (1 << TWINT)));

    if ((TWSR & TW_NO_INFO) != TW_MR_DATA_ACK)

    {

        return TWI__ERROR__ERROR;

    }

    *p_data = TWDR;

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn twi__error_t twi__receive_data_nack(uint8_t* p_data)

 *

 * \brief

 *

 * \param   p_data

 ******************************************************************************/

twi__error_t

twi__receive_data_nack

(

    uint8_t* p_data

){

    // Check the preconditions.

    assert(NULL != p_data);

    TWCR = (1 << TWEN) | (1 << TWINT);

    while (!(TWCR & (1 << TWINT)));

    if ((TWSR & TW_NO_INFO) != TW_MR_DATA_NACK)

    {

        return TWI__ERROR__ERROR;

    }

    *p_data = TWDR;

    return TWI__ERROR__NONE;

}

/**************************************************************************//**

 * \fn void twi__stop(void)

 *

 * \brief Stop TWI.

 ******************************************************************************/

void

twi__stop

(

    void

){

    // Transmit stop operation.

    TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);

    // Wait for stop.

    while (TWCR & (1 << TWSTO));

}

/******************************************************************************

 * Private function definitions.

 ******************************************************************************/

/**************************************************************************//**

 * \fn static inline uint8_t twi__compute_bit_rate(

 * uint32_t f_scl,

 * uint8_t  prescaler_value)

 *

 * \brief

 *

 * \param   f_scl           SCL frequency.

 * \param   prescaler_value Prescaler value.

 ******************************************************************************/

static inline

uint8_t

twi__compute_bit_rate

(

    uint32_t    f_scl,

    uint8_t     prescaler_value

){

    uint8_t bit_rate = (F_CPU - 16 * f_scl) / (2 * f_scl * prescaler_value);

    return bit_rate;

}