source: rtos_arduino/trunk/arduino_lib/hardware/arduino/samd/libraries/Wire/Wire.cpp@ 175

/*
 * TWI/I2C library for Arduino Zero
 * Copyright (c) 2015 Arduino LLC. All rights reserved.
 *
 * 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 2.1 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

extern "C" {
#include <string.h>
}

#include <Arduino.h>
#include <wiring_private.h>

#include "Wire.h"

TwoWire::TwoWire(SERCOM * s, uint8_t pinSDA, uint8_t pinSCL)
{
  this->sercom = s;
  this->_uc_pinSDA=pinSDA;
  this->_uc_pinSCL=pinSCL;
  transmissionBegun = false;
}

void TwoWire::begin(void) {
  //Master Mode
  sercom->initMasterWIRE(TWI_CLOCK);
  sercom->enableWIRE();

  pinPeripheral(_uc_pinSDA, g_APinDescription[_uc_pinSDA].ulPinType);
  pinPeripheral(_uc_pinSCL, g_APinDescription[_uc_pinSCL].ulPinType);
}

void TwoWire::begin(uint8_t address) {
  //Slave mode
  sercom->initSlaveWIRE(address);
  sercom->enableWIRE();

  pinPeripheral(_uc_pinSDA, g_APinDescription[_uc_pinSDA].ulPinType);
  pinPeripheral(_uc_pinSCL, g_APinDescription[_uc_pinSCL].ulPinType);
}

void TwoWire::setClock(uint32_t baudrate) {
  sercom->disableWIRE();
  sercom->initMasterWIRE(baudrate);
  sercom->enableWIRE();
}

void TwoWire::end() {
  sercom->disableWIRE();
}

uint8_t TwoWire::requestFrom(uint8_t address, size_t quantity, bool stopBit)
{
  if(quantity == 0)
  {
    return 0;
  }

  size_t byteRead = 0;

  if(sercom->startTransmissionWIRE(address, WIRE_READ_FLAG))
  {
    // Read first data
    rxBuffer.store_char(sercom->readDataWIRE());

    // Connected to slave
    for (byteRead = 1; byteRead < quantity; ++byteRead)
    {
      sercom->prepareAckBitWIRE();                          // Prepare Acknowledge
      sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_READ); // Prepare the ACK command for the slave
      rxBuffer.store_char(sercom->readDataWIRE());          // Read data and send the ACK
    }
    sercom->prepareNackBitWIRE();                           // Prepare NACK to stop slave transmission
    //sercom->readDataWIRE();                               // Clear data register to send NACK

    if (stopBit)
    {
      sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_STOP);   // Send Stop
    }
  }

  return byteRead;
}

uint8_t TwoWire::requestFrom(uint8_t address, size_t quantity)
{
  return requestFrom(address, quantity, true);
}

void TwoWire::beginTransmission(uint8_t address) {
  // save address of target and clear buffer
  txAddress = address;
  txBuffer.clear();

  transmissionBegun = true;
}

// Errors:
//  0 : Success
//  1 : Data too long
//  2 : NACK on transmit of address
//  3 : NACK on transmit of data
//  4 : Other error
uint8_t TwoWire::endTransmission(bool stopBit)
{
  transmissionBegun = false ;

  // Start I2C transmission
  if ( !sercom->startTransmissionWIRE( txAddress, WIRE_WRITE_FLAG ) )
  {
    sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_STOP);
    return 2 ;  // Address error
  }

  // Send all buffer
  while( txBuffer.available() )
  {
    // Trying to send data
    if ( !sercom->sendDataMasterWIRE( txBuffer.read_char() ) )
    {
      sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_STOP);
      return 3 ;  // Nack or error
    }
  }
  
  if (stopBit)
  {
    sercom->prepareCommandBitsWire(WIRE_MASTER_ACT_STOP);
  }   

  return 0;
}

uint8_t TwoWire::endTransmission()
{
  return endTransmission(true);
}

size_t TwoWire::write(uint8_t ucData)
{
  if(sercom->isMasterWIRE())
  {
    // No writing, without begun transmission or a full buffer
    if ( !transmissionBegun || txBuffer.isFull() )
    {
      return 0 ;
    }

    txBuffer.store_char( ucData ) ;

    return 1 ;
  }
  else
  {
    if(sercom->sendDataSlaveWIRE( ucData ))
    {
      return 1;
    }
  }

  return 0;
}

size_t TwoWire::write(const uint8_t *data, size_t quantity)
{
  //Try to store all data
  for(size_t i = 0; i < quantity; ++i)
  {
    //Return the number of data stored, when the buffer is full (if write return 0)
    if(!write(data[i]))
      return i;
  }

  //All data stored
  return quantity;
}

int TwoWire::available(void)
{
  return rxBuffer.available();
}

int TwoWire::read(void)
{
  return rxBuffer.read_char();
}

int TwoWire::peek(void)
{
  return rxBuffer.peek();
}

void TwoWire::flush(void)
{
  // Do nothing, use endTransmission(..) to force
  // data transfer.
}

void TwoWire::onReceive(void(*function)(int))
{
  onReceiveCallback = function;
}

void TwoWire::onRequest(void(*function)(void))
{
  onRequestCallback = function;
}

void TwoWire::onService(void)
{
  if ( sercom->isSlaveWIRE() )
  {
    if(sercom->isStopDetectedWIRE() || 
        (sercom->isAddressMatch() && sercom->isRestartDetectedWIRE() && !sercom->isMasterReadOperationWIRE())) //Stop or Restart detected
    {
      sercom->prepareAckBitWIRE();
      sercom->prepareCommandBitsWire(0x03);

      //Calling onReceiveCallback, if exists
      if(onReceiveCallback)
      {
        onReceiveCallback(available());
      }
      
      rxBuffer.clear();
    }
    else if(sercom->isAddressMatch())  //Address Match
    {
      sercom->prepareAckBitWIRE();
      sercom->prepareCommandBitsWire(0x03);

      if(sercom->isMasterReadOperationWIRE()) //Is a request ?
      {
        // wait for data ready flag,
        // before calling request callback
        while(!sercom->isDataReadyWIRE());

        //Calling onRequestCallback, if exists
        if(onRequestCallback)
        {
          onRequestCallback();
        }
      }
    }
    else if(sercom->isDataReadyWIRE()) //Received data
    {
      if (rxBuffer.isFull()) {
        sercom->prepareNackBitWIRE(); 
      } else {
        //Store data
        rxBuffer.store_char(sercom->readDataWIRE());

        sercom->prepareAckBitWIRE(); 
      }

      sercom->prepareCommandBitsWire(0x03);
    }
  }
}

#if WIRE_INTERFACES_COUNT > 0
  /* In case new variant doesn't define these macros,
   * we put here the ones for Arduino Zero.
   *
   * These values should be different on some variants!
   */
  #ifndef PERIPH_WIRE
    #define PERIPH_WIRE          sercom3
    #define WIRE_IT_HANDLER      SERCOM3_Handler
  #endif // PERIPH_WIRE
  TwoWire Wire(&PERIPH_WIRE, PIN_WIRE_SDA, PIN_WIRE_SCL);

  void WIRE_IT_HANDLER(void) {
    Wire.onService();
  }
#endif

#if WIRE_INTERFACES_COUNT > 1
  TwoWire Wire1(&PERIPH_WIRE1, PIN_WIRE1_SDA, PIN_WIRE1_SCL);

  void WIRE1_IT_HANDLER(void) {
    Wire1.onService();
  }
#endif

#if WIRE_INTERFACES_COUNT > 2
  TwoWire Wire2(&PERIPH_WIRE2, PIN_WIRE2_SDA, PIN_WIRE2_SCL);

  void WIRE2_IT_HANDLER(void) {
    Wire2.onService();
  }
#endif

#if WIRE_INTERFACES_COUNT > 3
  TwoWire Wire3(&PERIPH_WIRE3, PIN_WIRE3_SDA, PIN_WIRE3_SCL);

  void WIRE3_IT_HANDLER(void) {
    Wire3.onService();
  }
#endif

#if WIRE_INTERFACES_COUNT > 4
  TwoWire Wire4(&PERIPH_WIRE4, PIN_WIRE4_SDA, PIN_WIRE4_SCL);

  void WIRE4_IT_HANDLER(void) {
    Wire4.onService();
  }
#endif

#if WIRE_INTERFACES_COUNT > 5
  TwoWire Wire5(&PERIPH_WIRE5, PIN_WIRE5_SDA, PIN_WIRE5_SCL);

  void WIRE5_IT_HANDLER(void) {
    Wire5.onService();
  }
#endif