TinyWireM.h

/*
  TinyWireM.h - a wrapper(+) class for TWI/I2C Master library for the ATtiny on Arduino
  1/21/2011 BroHogan -  brohoganx10 at gmail dot com

  Thanks to 'jkl' for the gcc version of Atmel's USI_TWI_Master code
  http://www.cs.cmu.edu/~dst/ARTSI/Create/PC%20Comm/
  I added Atmel's original Device dependant defines section back into USI_TWI_Master.h
 
 
 NOTE! - It's very important to use pullups on the SDA & SCL lines! More so than with the Wire lib.
 
 USAGE is modeled after the standard Wire library . . .
  Put in setup():
	TinyWireM.begin(){                               // initialize I2C lib
  To Send:
	TinyWireM.beginTransmission(uint8_t slaveAddr){  // setup slave's address (7 bit address - same as Wire)
	TinyWireM.send(uint8_t data){                    // buffer up bytes to send - can be called multiple times
	someByte = TinyWireM.endTransmission(){          // actually send the bytes in the buffer
	                                                 // returns (optional) 0 = sucess or see USI_TWI_Master.h for error codes
  To Receive:
	someByte = TinyWireM.requestFrom(uint8_t slaveAddr, uint8_t numBytes){      // reads 'numBytes' from slave's address
	                                                 // (usage optional) returns 0= success or see USI_TWI_Master.h for error codes
	someByte = TinyWireM.receive(){                  // returns the next byte in the received buffer - called multiple times
	someByte = TinyWireM.available(){                // returns the number of unread bytes in the received buffer

	TODO:	(by others!)
	- merge this class with TinyWireS for master & slave support in one 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 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.
*/

#ifndef TinyWireM_h
#define TinyWireM_h

#include <inttypes.h>
#include "Arduino.h"
#define USI_SEND         0              // indicates sending to TWI
#define USI_RCVE         1              // indicates receiving from TWI
#define USI_BUF_SIZE    16              // bytes in message buffer

//class USI_TWI : public Stream
class USI_TWI
{
  private:
    static uint8_t USI_Buf[];           // holds I2C send and receive data
    static uint8_t USI_BufIdx;          // current number of bytes in the send buff
    static uint8_t USI_LastRead;        // number of bytes read so far
    static uint8_t USI_BytesAvail;      // number of bytes requested but not read
	
  public:
    USI_TWI();
    void    begin();
    void    beginTransmission(uint8_t);
    size_t  write(uint8_t);
    inline size_t write(uint8_t* d, uint8_t n) { uint16_t i; for (i = 0; i < n; i++) write(d[i]); return (size_t)n; }
    inline size_t write(unsigned long n) { return write((uint8_t)n); }
    inline size_t write(long n) { return write((uint8_t)n); }
    inline size_t write(unsigned int n) { return write((uint8_t)n); }
    inline size_t write(int n) { return write((uint8_t)n); }
    void send(uint8_t b)               { write(b); }
    void send(uint8_t *d, uint8_t n)   { write(d, n); }
    void send(int n)                   { write((uint8_t)n); }
    uint8_t endTransmission();
    uint8_t endTransmission(uint8_t);
    uint8_t requestFrom(uint8_t, uint8_t);
    int     read(); 
    int     available(); 
    int     peek(void);
    void    flush(void);
    uint8_t receive(void) {
        int c = read();
        if (c < 0) return 0;
        return c;
    }
};

extern USI_TWI TinyWireM;

#endif //TinyWireM_h