TinyWireM.cpp

/*!
 * @file TinyWireM.cpp
 *
 * @mainpage Adafruit TinyWireM Library
 *
 * @section intro_sec Introduction
 *
 * TinyWireM.cpp - a wrapper class for TWI/I2C Master library for the ATtiny on
 * Arduino 1/21/2011 BroHogan -  brohoganx10 at gmail dot com
 *
 * **** See TinyWireM.h for Credits and Usage information ****
 *
 * @section license License
 *
 * 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 2.1 of the License, or 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.
 */

extern "C" {
//#include "USI_TWI_Master.h"
//#include <USI_TWI_Master.h>
//#include <USI_TWI_Master\USI_TWI_Master.h>
//#include <USI_TWI_Master/USI_TWI_Master.h>
}

#include "TinyWireM.h"
#include "USI_TWI_Master.h"

// Initialize Class Variables //////////////////////////////////////////////////
uint8_t USI_TWI::USI_Buf[USI_BUF_SIZE]; // holds I2C send and receive data
uint8_t USI_TWI::USI_BufIdx = 0;     // current number of bytes in the send buff
uint8_t USI_TWI::USI_LastRead = 0;   // number of bytes read so far
uint8_t USI_TWI::USI_BytesAvail = 0; // number of bytes requested but not read

// Constructors ////////////////////////////////////////////////////////////////

USI_TWI::USI_TWI() {}

// Public Methods //////////////////////////////////////////////////////////////

// int USI_TWI::peek(){}
// void USI_TWI::flush(){}

void USI_TWI::begin() { // initialize I2C lib
  USI_TWI_Master_Initialise();
}

void USI_TWI::beginTransmission(
    uint8_t slaveAddr) { // setup address & write bit
  USI_BufIdx = 0;
  USI_Buf[USI_BufIdx] = (slaveAddr << TWI_ADR_BITS) | USI_SEND;
}

size_t USI_TWI::write(uint8_t data) { // buffers up data to send
  if (USI_BufIdx >= USI_BUF_SIZE - 1)
    return 0;   // dont blow out the buffer
  USI_BufIdx++; // inc for next byte in buffer
  USI_Buf[USI_BufIdx] = data;
  return 1;
}

uint8_t USI_TWI::endTransmission() { return endTransmission(1); }

uint8_t USI_TWI::endTransmission(uint8_t stop) { // actually sends the buffer
  bool xferOK = false;
  uint8_t errorCode = 0;
  xferOK = USI_TWI_Start_Read_Write(
      USI_Buf, USI_BufIdx + 1); // core func that does the work
  USI_BufIdx = 0;
  if (xferOK) {
    if (stop) {
      errorCode = USI_TWI_Master_Stop();
      if (errorCode == 0) {
        errorCode = USI_TWI_Get_State_Info();
        return errorCode;
      }
    }
    return 0;
  } else { // there was an error
    errorCode =
        USI_TWI_Get_State_Info(); // this function returns the error number
    return errorCode;
  }
}

uint8_t
USI_TWI::requestFrom(uint8_t slaveAddr,
                     uint8_t numBytes) { // setup for receiving from slave
  bool xferOK = false;
  uint8_t errorCode = 0;
  USI_LastRead = 0;
  USI_BytesAvail = numBytes; // save this off in a global
  numBytes++;                // add extra byte to transmit header
  USI_Buf[0] =
      (slaveAddr << TWI_ADR_BITS) | USI_RCVE; // setup address & Rcve bit
  xferOK = USI_TWI_Start_Read_Write(USI_Buf,
                                    numBytes); // core func that does the work
  // USI_Buf now holds the data read
  if (xferOK) {
    errorCode = USI_TWI_Master_Stop();
    if (errorCode == 0) {
      errorCode = USI_TWI_Get_State_Info();
      return errorCode;
    }
    return 0;
  } else { // there was an error
    errorCode =
        USI_TWI_Get_State_Info(); // this function returns the error number
    return errorCode;
  }
}

int USI_TWI::read() { // returns the bytes received one at a time
  USI_LastRead++;     // inc first since first uint8_t read is in USI_Buf[1]
  return USI_Buf[USI_LastRead];
}

int USI_TWI::available() { // the bytes available that haven't been read yet
  return USI_BytesAvail - (USI_LastRead);
}

void USI_TWI::end() { USI_TWI_Master_Stop(); }

// Preinstantiate Objects //////////////////////////////////////////////////////

/*!
 * @brief Makes TinyWireM an object of USI_TWI
 */
USI_TWI TinyWireM = USI_TWI();