RIOT/cpu/atmega_common/periph/i2c.c

/*
 * Copyright (C) 2017 Hamburg University of Applied Sciences, Dimitri Nahm
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */

/**
 * @addtogroup  driver_periph
 * @{
 *
 * @file
 * @brief       Low-level I2C driver implementation fot atmega common
 *
 * @note This implementation only implements the 7-bit addressing mode.
 *
 * @author      Dimitri Nahm <dimitri.nahm@haw-hamburg.de>
 *
 * @}
 */

#include <stdint.h>

#include "cpu.h"
#include "mutex.h"
#include "periph/i2c.h"
#include "periph_conf.h"

#define ENABLE_DEBUG    (0)
#include "debug.h"

#define MT_START 0x08
#define MT_ADDRESS_ACK 0x18
#define MT_DATA_ACK 0x28
#define MR_ADDRESS_ACK 0x40

/* guard file in case no I2C device is defined */
#if I2C_NUMOF

/* static function definitions */
static int _start(uint8_t address, uint8_t rw_flag);
static int _write(const uint8_t *data, int length);
static void _stop(void);

/**
 * @brief Array holding one pre-initialized mutex for each I2C device
 */
static mutex_t locks[] =  {
#if I2C_0_EN
    [I2C_0] = MUTEX_INIT,
#endif
};

int i2c_init_master(i2c_t dev, i2c_speed_t speed)
{
    /* TWI Bit Rate Register - division factor for the bit rate generator*/
    int twibrr;

    /* check if the line is valid */
    if (dev >= I2C_NUMOF) {
        return -1;
    }

    /* calculate speed configuration */
    switch (speed) {
        case I2C_SPEED_NORMAL:
            twibrr = ((CLOCK_CORECLOCK/100000)-16)/2;
            break;

        case I2C_SPEED_FAST:
            twibrr = ((CLOCK_CORECLOCK/400000)-16)/2;
            break;

        default:
            return -2;
    }

    /* set pull-up on SCL and SDA */
    #if defined (CPU_ATMEGA2560) || defined (CPU_ATMEGA1281)
        PORTD |= (1 << PORTD0) | (1 << PORTD1);
    #endif
    #ifdef CPU_ATMEGA328P
        PORTC |= (1 << PORTC4) | (1 << PORTC5);
    #endif

    /* enable I2C clock */
    i2c_poweron(dev);

    /* disable device */
    TWCR &= ~(1 << TWEN);
    /* configure I2C clock */
    TWBR = twibrr;
    /* enable device */
    TWCR |= (1 << TWEN);

    return 0;
}

int i2c_acquire(i2c_t dev)
{
    if (dev >= I2C_NUMOF) {
        return -1;
    }
    mutex_lock(&locks[dev]);
    return 0;
}

int i2c_release(i2c_t dev)
{
    if (dev >= I2C_NUMOF) {
        return -1;
    }
    mutex_unlock(&locks[dev]);
    return 0;
}

int i2c_read_byte(i2c_t dev, uint8_t address, void *data)
{
    return i2c_read_bytes(dev, address, data, 1);
}

int i2c_read_bytes(i2c_t dev, uint8_t address, void *data, int length)
{
    uint8_t *my_data = data;

    if ((unsigned int)dev >= I2C_NUMOF) {
        return -1;
    }

    /* send start condition and slave address */
    if (_start(address, I2C_FLAG_READ) != 0)
        return 0;

    for (int i = 0; i < length; i++) {
        /* Send NACK for last received byte */
        if ((length-i) == 1)
            TWCR = (1 << TWEN) | (1 << TWINT);
        else
            TWCR = (1 << TWEA) | (1 << TWEN) | (1 << TWINT);
        DEBUG("Wait for byte %i\n", i+1);
        /* Wait for TWINT Flag set. This indicates that DATA has been received.*/
        while (!(TWCR & (1 << TWINT)))
            {}
        /* receive data byte */
        my_data[i] = TWDR;
        DEBUG("Byte %i received\n", i+1);
    }

    /* end transmission */
    _stop();

    return length;
}

int i2c_read_reg(i2c_t dev, uint8_t address, uint8_t reg, void *data)
{
    return i2c_read_regs(dev, address, reg, data, 1);
}

int i2c_read_regs(i2c_t dev, uint8_t address, uint8_t reg, void *data, int length)
{
    if ((unsigned int)dev >= I2C_NUMOF) {
        return -1;
    }

    /* start transmission and send slave address */
    if (_start(address, I2C_FLAG_WRITE) != 0)
        return 0;

    /* send register address and wait for complete transfer to be finished*/
    if (_write(&reg, 1) != 1) {
        _stop();
        return 0;
    }

    _stop();

    /* now start a new start condition and receive data */
    return i2c_read_bytes(dev, address, data, length);
}

int i2c_write_byte(i2c_t dev, uint8_t address, uint8_t data)
{
    return i2c_write_bytes(dev, address, &data, 1);
}

int i2c_write_bytes(i2c_t dev, uint8_t address, const void *data, int length)
{
    int bytes = 0;

    if ((unsigned int)dev >= I2C_NUMOF) {
        return -1;
    }

    /* start transmission and send slave address */
    if (_start(address, I2C_FLAG_WRITE) != 0)
        return 0;

    /* send out data bytes */
    bytes = _write(data, length);

    /* end transmission */
    _stop();

    return bytes;
}

int i2c_write_reg(i2c_t dev, uint8_t address, uint8_t reg, uint8_t data)
{
    if ((unsigned int)dev >= I2C_NUMOF) {
        return -1;
    }

    return i2c_write_regs(dev, address, reg, &data, 1);
}

int i2c_write_regs(i2c_t dev, uint8_t address, uint8_t reg, const void *data, int length)
{
    int bytes = 0;

    if ((unsigned int)dev >= I2C_NUMOF) {
        return -1;
    }

    /* start transmission and send slave address */
    if (_start(address, I2C_FLAG_WRITE) != 0)
        return 0;
    /* send register address and wait for complete transfer to be finished*/
    if (_write(&reg, 1))
        /* write data to register */
        bytes = _write(data, length);
    /* finish transfer */
    _stop();
    /* return number of bytes send */
    return bytes;
}

void i2c_poweron(i2c_t dev)
{
    if (dev < I2C_NUMOF) {
        #if defined (CPU_ATMEGA2560) || defined (CPU_ATMEGA1281)
            PRR0 &= ~(1 << PRTWI);
        #endif
        #ifdef CPU_ATMEGA328P
            PRR &= ~(1 << PRTWI);
        #endif
    }
}

void i2c_poweroff(i2c_t dev)
{
    if (dev < I2C_NUMOF) {
        #if defined (CPU_ATMEGA2560) || defined (CPU_ATMEGA1281)
            PRR0 |= (1 << PRTWI);
        #endif
        #ifdef CPU_ATMEGA328P
            PRR |= (1 << PRTWI);
        #endif
    }
}

static int _start(uint8_t address, uint8_t rw_flag)
{
    /* Reset I2C Interrupt Flag and transmit START condition */
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
    DEBUG("START condition transmitted\n");

    /* Wait for TWINT Flag set. This indicates that the START 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 START go to ERROR */
    if ((TWSR & 0xF8) != MT_START) {
        DEBUG("I2C Status Register is different from START\n");
        _stop();
        return -1;
    }
    else
        DEBUG("I2C Status Register is: START\n");

    /* Load ADDRESS and R/W Flag into TWDR Register.
    Clear TWINT bit in TWCR to start transmission of ADDRESS */
    TWDR = (address << 1) | rw_flag;
    TWCR = (1 << TWINT) | (1 << TWEN);
    DEBUG("ADDRESS and FLAG transmitted\n");

    /* Wait for TWINT Flag set. This indicates that ADDRESS has been transmitted.*/
    while (!(TWCR & (1 << TWINT)))
        {}

    /* Check value of TWI Status Register. Mask prescaler bits.
    If status different from ADDRESS ACK go to ERROR */
    if ((TWSR & 0xF8) == MT_ADDRESS_ACK)
        DEBUG("ACK has been received for ADDRESS (write)\n");
    else if ((TWSR & 0xF8) == MR_ADDRESS_ACK)
        DEBUG("ACK has been received for ADDRESS (read)\n");
    else {
        DEBUG("NOT ACK has been received for ADDRESS\n");
        _stop();
        return -2;
    }

    return 0;
}

static int _write(const uint8_t *data, int length)
{
    int i = 0;

    for (i = 0; i < length; i++) {
        /* Load DATA into TWDR Register.
        Clear TWINT bit in TWCR to start transmission of data */
        TWDR = data[i];
        TWCR = (1 << TWINT) | (1 << TWEN);
        DEBUG("Byte %i transmitted\n", i+1);

        /* Wait for TWINT Flag set. This indicates that DATA has been transmitted.*/
        while (!(TWCR & (1 << TWINT)))
            {}

        /* Check value of TWI Status Register. Mask prescaler bits. If status
        different from MT_DATA_ACK, return number of transmitted bytes */
        if ((TWSR & 0xF8) != MT_DATA_ACK) {
            DEBUG("NACK has been received for BYTE %i\n", i+1);
            return i;
        }
        else
            DEBUG("ACK has been received for BYTE %i\n", i+1);
    }

    return i;
}

static void _stop(void)
{
    /* Reset I2C Interrupt Flag and transmit STOP condition */
    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
    while (TWCR & (1 << TWSTO))
        {}
    DEBUG("STOP condition transmitted\n");
    TWCR = 0;
}

#endif /* I2C_NUMOF */