I2cMaster.cpp

/* Arduino I2cMaster Library
 * Copyright (C) 2010 by William Greiman
 *
 * This file is part of the Arduino I2cMaster Library
 *
 * This Library 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 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the Arduino I2cMaster Library.  If not, see
 * <http://www.gnu.org/licenses/>.
 */
#include "I2cMaster.h"
#include "TwiMap.h"
//==============================================================================
// WARNING don't change SoftI2cMaster unless you verify the change with a scope
//------------------------------------------------------------------------------
/**
 * Initialize SCL/SDA pins and set the bus high.
 *
 * \param[in] sdaPin The software SDA pin number.
 *
 * \param[in] sclPin The software SCL pin number.
 */
SoftI2cMaster::SoftI2cMaster(uint8_t sdaPin, uint8_t sclPin) {
  sdaPin_ = sdaPin;
  pinMode(sdaPin_, OUTPUT);
  digitalWrite(sdaPin_, HIGH);
  sclPin_ = sclPin;
  pinMode(sclPin_, OUTPUT);
  digitalWrite(sclPin_, HIGH);
}
//------------------------------------------------------------------------------
/** Read a byte and send Ack if more reads follow else Nak to terminate read.
 *
 * \param[in] last Set true to terminate the read else false.
 *
 * \return The byte read from the I2C bus.
 */
uint8_t SoftI2cMaster::read(uint8_t last) {
  uint8_t b = 0;
  // make sure pull-up enabled
  digitalWrite(sdaPin_, HIGH);
  pinMode(sdaPin_, INPUT);
  // read byte
  for (uint8_t i = 0; i < 8; i++) {
    // don't change this loop unless you verify the change with a scope
    b <<= 1;
    delayMicroseconds(I2C_DELAY_USEC);
    digitalWrite(sclPin_, HIGH);
    if (digitalRead(sdaPin_)) b |= 1;
    digitalWrite(sclPin_, LOW);
  }
  // send Ack or Nak
  pinMode(sdaPin_, OUTPUT);
  digitalWrite(sdaPin_, last);
  digitalWrite(sclPin_, HIGH);
  delayMicroseconds(I2C_DELAY_USEC);
  digitalWrite(sclPin_, LOW);
  digitalWrite(sdaPin_, LOW);
  return b;
}
//------------------------------------------------------------------------------
/** Issue a restart condition.
 *
 * \param[in] addressRW I2C address with read/write bit.
 *
 * \return The value true, 1, for success or false, 0, for failure.
 */
bool SoftI2cMaster::restart(uint8_t addressRW) {
  digitalWrite(sdaPin_, HIGH);
  digitalWrite(sclPin_, HIGH);
  delayMicroseconds(I2C_DELAY_USEC);
  return start(addressRW);
}
//------------------------------------------------------------------------------
/** Issue a start condition.
 *
 * \param[in] addressRW I2C address with read/write bit.
 *
 * \return The value true, 1, for success or false, 0, for failure.
 */
bool SoftI2cMaster::start(uint8_t addressRW) {
  digitalWrite(sdaPin_, LOW);
  delayMicroseconds(I2C_DELAY_USEC);
  digitalWrite(sclPin_, LOW);
  return write(addressRW);
}
//------------------------------------------------------------------------------
  /**  Issue a stop condition. */
void SoftI2cMaster::stop(void) {
  digitalWrite(sdaPin_, LOW);
  delayMicroseconds(I2C_DELAY_USEC);
  digitalWrite(sclPin_, HIGH);
  delayMicroseconds(I2C_DELAY_USEC);
  digitalWrite(sdaPin_, HIGH);
  delayMicroseconds(I2C_DELAY_USEC);
}
//------------------------------------------------------------------------------
/**
 * Write a byte.
 *
 * \param[in] data The byte to send.
 *
 * \return The value true, 1, if the slave returned an Ack or false for Nak.
 */
bool SoftI2cMaster::write(uint8_t data) {
  // write byte
  for (uint8_t m = 0X80; m != 0; m >>= 1) {
    // don't change this loop unless you verify the change with a scope
    digitalWrite(sdaPin_, m & data);
    digitalWrite(sclPin_, HIGH);
    delayMicroseconds(I2C_DELAY_USEC);
    digitalWrite(sclPin_, LOW);
  }
  // get Ack or Nak
  pinMode(sdaPin_, INPUT);
  // enable pullup
  digitalWrite(sdaPin_, HIGH);
  digitalWrite(sclPin_, HIGH);
  uint8_t rtn = digitalRead(sdaPin_);
  digitalWrite(sclPin_, LOW);
  pinMode(sdaPin_, OUTPUT);
  digitalWrite(sdaPin_, LOW);
  return rtn == 0;
}
//==============================================================================
void TwiMaster::execCmd(uint8_t cmdReg) {
  // send command
  TWCR = cmdReg;
  // wait for command to complete
  while (!(TWCR & (1 << TWINT)));
  // status bits.
  status_ = TWSR & 0xF8;
}
//------------------------------------------------------------------------------
/**
 * Initialize hardware TWI.
 *
 * \param[in] enablePullup Enable the AVR internal pull-ups. The internal
 *  pull-ups can, in some systems, eliminate the need for external pull-ups.
 */
TwiMaster::TwiMaster(bool enablePullup) {
  // no prescaler
  TWSR = 0;
  // set bit rate factor
  TWBR = (F_CPU/F_TWI - 16)/2;
  // enable pull-ups if requested
  if (enablePullup) {
    digitalWrite(TWI_SDA_PIN, HIGH);
    digitalWrite(TWI_SCL_PIN, HIGH);
  }
}
//------------------------------------------------------------------------------
/** Read a byte and send Ack if more reads follow else Nak to terminate read.
 *
 * \param[in] last Set true to terminate the read else false.
 *
 * \return The byte read from the I2C bus.
 */
uint8_t TwiMaster::read(uint8_t last) {
  execCmd((1 << TWINT) | (1 << TWEN) | (last ? 0 : (1 << TWEA)));
  return TWDR;
}
//------------------------------------------------------------------------------
/** Issue a restart condition.
 *
 * \param[in] addressRW I2C address with read/write bit.
 *
 * \return The value true, 1, for success or false, 0, for failure.
 */
bool TwiMaster::restart(uint8_t addressRW) {
  return start(addressRW);
}
//------------------------------------------------------------------------------
/** Issue a start condition.
 *
 * \param[in] addressRW I2C address with read/write bit.
 *
 * \return The value true for success or false for failure.
 */
bool TwiMaster::start(uint8_t addressRW) {
  // send START condition
  execCmd((1<<TWINT) | (1<<TWSTA) | (1<<TWEN));
  if (status() != TWSR_START && status() != TWSR_REP_START) return false;

  // send device address and direction
  TWDR = addressRW;
  execCmd((1 << TWINT) | (1 << TWEN));
  if (addressRW & I2C_READ) {
    return status() == TWSR_MRX_ADR_ACK;
  } else {
    return status() == TWSR_MTX_ADR_ACK;
  }
}
//------------------------------------------------------------------------------
/** Issue a stop condition. */
void TwiMaster::stop(void) {
  TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);

  // wait until stop condition is executed and bus released
  while (TWCR & (1 << TWSTO));
}
//------------------------------------------------------------------------------
/**
 * Write a byte.
 *
 * \param[in] data The byte to send.
 *
 * \return The value true, 1, if the slave returned an Ack or false for Nak.
 */
bool TwiMaster::write(uint8_t data) {
  TWDR = data;
  execCmd((1 << TWINT) | (1 << TWEN));
  return status() == TWSR_MTX_DATA_ACK;
}