MNC-IN12/src/i2c.c

/****************************************************
Low Level I2C Data Transreceiveing APIs

PLEASE SEE WWW.EXTREMEELECTRONICS.CO.IN FOR DETAILED
SCHEMATICS,USER GUIDE AND VIDOES.

COPYRIGHT (C) 2008-2009 EXTREME ELECTRONICS INDIA
****************************************************/

#include <avr/io.h>
#include "i2c.h"

/* Private defines */
// twi_br must be 3
#define TWI_SPEED       400000UL
#define TWI_PRESCALER   4
#define TWI_BR          ((F_CPU / TWI_SPEED) - 16) / (2 * TWI_PRESCALER)
#define TWPS_1          ((0<<TWPS1) | (0<<TWPS0))
#define TWPS_4          ((0<<TWPS1) | (1<<TWPS0))
#define TWPS_16         ((1<<TWPS1) | (0<<TWPS0))
#define TWPS_64         ((1<<TWPS1) | (1<<TWPS0))
#define TWI_PS          TWPS_4

#define TWI_WDT_TIMEOUT 10

/* Private variables */
uint8_t TWI_WDT;

/**
 * @brief Initialize TWI
 * @param None
 * @return None
 */
void I2C_Init(void) {
  //Set up TWI Module
  TWSR = TWI_PS;
  TWBR = TWI_BR;

  //Enable the TWI Module
  TWCR |= 1<<TWEN;
}

/**
 * @brief Disable TWI
 * @param None
 * @return None
 */
void I2C_Close(void)
{
  //Disable the module
  TWCR &= ~(1<<TWEN);
}

/**
 * @brief TWI Start condition
 * @param None
 * @return Operation status
 */
twi_stats_t I2C_Start(void) {
  //Put Start Condition on Bus
  TWCR= (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);

  //Poll Till Done
  TWI_WDT = TWI_WDT_TIMEOUT;
  while (!(TWCR & (1<<TWINT))) {
    if (TWI_WDT == 0) {
      return TWI_TIMEOUT;
    }
  }

  if ((TWSR & 0xF8) == 0x08 || (TWSR & 0xF8) == 0x10) {
    //start condition sent from master
    //or
    //repeat start condition sent from master
    return TWI_SUCCESS;
  } else {
    return TWI_ERROR;
  }

}

/**
 * @brief TWI Stop condition
 * @param None
 * @return Operation status
 */
twi_stats_t I2C_Stop(void) {
  //Put Stop Condition on bus
  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);

  //Wait for STOP to finish
  // зачем это ждать тут? проверять перед стартом и всё!
  TWI_WDT = TWI_WDT_TIMEOUT;
  while (TWCR & (1<<TWSTO)) {
    if (TWI_WDT == 0) {
      return TWI_TIMEOUT;
    }
  }
  return TWI_SUCCESS;
}

/**
 * @brief TWI Send Byte
 * @param None
 * @return Operation status
 */
twi_stats_t I2C_WriteByte(uint8_t data) {

  TWDR = data;

  //Initiate Transfer
  TWCR = (1<<TWEN) | (1<<TWINT);

  //Poll Till Done
  TWI_WDT = TWI_WDT_TIMEOUT;
  while (!(TWCR & (1<<TWINT))) {
    if (TWI_WDT == 0) {
      return TWI_TIMEOUT;
    }
  }

  //Check Status
  if ((TWSR & 0xF8) == 0x18 || (TWSR & 0xF8) == 0x28 || (TWSR & 0xF8) == 0x40) {
    //SLA+W Transmitted and ACK received
    //or
    //SLA+R Transmitted and ACK received
    //or
    //DATA Transmitted and ACK recived
    return TWI_SUCCESS;
  } else {
    return TWI_ERROR;  //Error
  }
}

/**
 * @brief TWI Receive Byte
 * @param None
 * @return Operation status
 */
twi_stats_t I2C_ReadByte(uint8_t *data, twi_ask_t ack) {
  //Set up ACK
  if (ack == TWI_ACK) {
    //return ACK after reception
    TWCR |= (1<<TWEA);
  } else {
    //return NACK after reception
    //Signals slave to stop giving more data
    //usually used for last byte read.
    TWCR &= ~(1<<TWEA);
  }

  //Now enable Reception of data by clearing TWINT
  TWCR |= (1<<TWINT);

  //Wait till done
  TWI_WDT = TWI_WDT_TIMEOUT;
  while(!(TWCR & (1<<TWINT))) {
    if (TWI_WDT == 0) {
      return TWI_TIMEOUT;
    }
  }

  //Check status
  if ((TWSR & 0xF8) == 0x58 || (TWSR & 0xF8) == 0x50) {
    //Data received and ACK returned
    //  or
    //Data received and NACK returned
    //Read the data
    *data = TWDR;
    return TWI_SUCCESS;
  } else {
    return TWI_ERROR;  //Error
  }
}