/*  Copyright (C) 2019 Elia Ritterbusch
 +
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
/* Library made by: g4lvanix
 * Github repository: https://github.com/g4lvanix/I2C-master-lib
 */

#include <avr/io.h>
#include <util/twi.h>

#include "i2c_master.h"
#include "timer.h"
#include "wait.h"

#ifndef F_SCL
#  define F_SCL 400000UL  // SCL frequency
#endif
#define Prescaler 1
#define TWBR_val ((((F_CPU / F_SCL) / Prescaler) - 16) / 2)

void i2c_init(void) {
  TWSR = 0; /* no prescaler */
  TWBR = (uint8_t)TWBR_val;

  #ifdef __AVR_ATmega32A__
  // set pull-up resistors on I2C bus pins
  PORTC |= 0b11;

  // enable TWI (two-wire interface)
  TWCR |= (1 << TWEN);

  // enable TWI interrupt and slave address ACK
  TWCR |= (1 << TWIE);
  TWCR |= (1 << TWEA);
  #endif
}

i2c_status_t i2c_start(uint8_t address, uint16_t timeout) {
  // reset TWI control register
  TWCR = 0;
  // transmit START condition
  TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);

  uint16_t timeout_timer = timer_read();
  while (!(TWCR & (1 << TWINT))) {
    if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
      return I2C_STATUS_TIMEOUT;
    }
  }

  // check if the start condition was successfully transmitted
  if (((TW_STATUS & 0xF8) != TW_START) && ((TW_STATUS & 0xF8) != TW_REP_START)) {
    return I2C_STATUS_ERROR;
  }

  // load slave address into data register
  TWDR = address;
  // start transmission of address
  TWCR = (1 << TWINT) | (1 << TWEN);

  timeout_timer = timer_read();
  while (!(TWCR & (1 << TWINT))) {
    if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
      return I2C_STATUS_TIMEOUT;
    }
  }

  // check if the device has acknowledged the READ / WRITE mode
  uint8_t twst = TW_STATUS & 0xF8;
  if ((twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK)) {
    return I2C_STATUS_ERROR;
  }

  return I2C_STATUS_SUCCESS;
}

i2c_status_t i2c_write(uint8_t data, uint16_t timeout) {
  // load data into data register
  TWDR = data;
  // start transmission of data
  TWCR = (1 << TWINT) | (1 << TWEN);

  uint16_t timeout_timer = timer_read();
  while (!(TWCR & (1 << TWINT))) {
    if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
      return I2C_STATUS_TIMEOUT;
    }
  }

  if ((TW_STATUS & 0xF8) != TW_MT_DATA_ACK) {
    return I2C_STATUS_ERROR;
  }

  return I2C_STATUS_SUCCESS;
}

int16_t i2c_read_ack(uint16_t timeout) {
  // start TWI module and acknowledge data after reception
  TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWEA);

  uint16_t timeout_timer = timer_read();
  while (!(TWCR & (1 << TWINT))) {
    if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
      return I2C_STATUS_TIMEOUT;
    }
  }

  // return received data from TWDR
  return TWDR;
}

int16_t i2c_read_nack(uint16_t timeout) {
  // start receiving without acknowledging reception
  TWCR = (1 << TWINT) | (1 << TWEN);

  uint16_t timeout_timer = timer_read();
  while (!(TWCR & (1 << TWINT))) {
    if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
      return I2C_STATUS_TIMEOUT;
    }
  }

  // return received data from TWDR
  return TWDR;
}

i2c_status_t i2c_transmit(uint8_t address, const uint8_t* data, uint16_t length, uint16_t timeout) {
  i2c_status_t status = i2c_start(address | I2C_WRITE, timeout);

  for (uint16_t i = 0; i < length && status >= 0; i++) {
    status = i2c_write(data[i], timeout);
  }

  i2c_stop();

  return status;
}

i2c_status_t i2c_receive(uint8_t address, uint8_t* data, uint16_t length, uint16_t timeout) {
  i2c_status_t status = i2c_start(address | I2C_READ, timeout);

  for (uint16_t i = 0; i < (length - 1) && status >= 0; i++) {
    status = i2c_read_ack(timeout);
    if (status >= 0) {
      data[i] = status;
    }
  }

  if (status >= 0) {
    status = i2c_read_nack(timeout);
    if (status >= 0) {
      data[(length - 1)] = status;
    }
  }

  i2c_stop();

  return (status < 0) ? status : I2C_STATUS_SUCCESS;
}

i2c_status_t i2c_writeReg(uint8_t devaddr, uint8_t regaddr, const uint8_t* data, uint16_t length, uint16_t timeout) {
  i2c_status_t status = i2c_start(devaddr | 0x00, timeout);
  if (status >= 0) {
    status = i2c_write(regaddr, timeout);

    for (uint16_t i = 0; i < length && status >= 0; i++) {
      status = i2c_write(data[i], timeout);
    }
  }

  i2c_stop();

  return status;
}

i2c_status_t i2c_readReg(uint8_t devaddr, uint8_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout) {
  i2c_status_t status = i2c_start(devaddr, timeout);
  if (status < 0) {
    goto error;
  }

  status = i2c_write(regaddr, timeout);
  if (status < 0) {
    goto error;
  }

  status = i2c_start(devaddr | 0x01, timeout);

  for (uint16_t i = 0; i < (length - 1) && status >= 0; i++) {
    status = i2c_read_ack(timeout);
    if (status >= 0) {
      data[i] = status;
    }
  }

  if (status >= 0) {
    status = i2c_read_nack(timeout);
    if (status >= 0) {
      data[(length - 1)] = status;
    }
  }

error:
  i2c_stop();

  return (status < 0) ? status : I2C_STATUS_SUCCESS;
}

void i2c_stop(void) {
  // transmit STOP condition
  TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
}