SoftwareWire.h

#ifndef SoftwareWire_h
#define SoftwareWire_h

#include <Arduino.h>


// Transmission status error, the return value of endTransmission()
#define SOFTWAREWIRE_NO_ERROR       0
#define SOFTWAREWIRE_BUFFER_FULL    1
#define SOFTWAREWIRE_ADDRESS_NACK   2
#define SOFTWAREWIRE_DATA_NACK      3
#define SOFTWAREWIRE_OTHER          4

#define SOFTWAREWIRE_BUFSIZE 32        // same as buffer size of Arduino Wire library


class SoftwareWire
{
public:
  SoftwareWire();
  SoftwareWire(uint8_t sdaPin, uint8_t sclPin, boolean pullups = true, boolean detectClockStretch = true);
  ~SoftwareWire();
  void end();

  void begin();

  // Generate compile error when slave mode begin(address) is used
  void __attribute__ ((error("I2C/TWI Slave mode is not supported by the SoftwareWire library"))) begin(uint8_t addr);
  void __attribute__ ((error("I2C/TWI Slave mode is not supported by the SoftwareWire library"))) begin(int addr);

  void setClock(uint32_t clock);
  void beginTransmission(uint8_t address);
  void beginTransmission(int address);
  uint8_t endTransmission(boolean sendStop = true);
  uint8_t requestFrom(uint8_t address, uint8_t size, boolean sendStop = true);
  uint8_t requestFrom(int address, int size, boolean sendStop = true);
  size_t write(uint8_t data);
  size_t write(const uint8_t *data, size_t quantity);
  int available(void);
  int read(void);
  int readBytes(uint8_t* buf, uint8_t size);
  int readBytes(char * buf, uint8_t size);
  int readBytes(char * buf, int size);
  int peek(void);
  void setTimeout(long timeout);  // timeout to wait for the I2C bus
  void printStatus(Print& Ser);   // print information using specified object class


private:
  // per object data

  uint8_t _sdaPin;
  uint8_t _sclPin;
  uint8_t _sdaBitMask;
  uint8_t _sclBitMask;

  volatile uint8_t *_sdaPortReg;
  volatile uint8_t *_sclPortReg;
  volatile uint8_t *_sdaDirReg;
  volatile uint8_t *_sclDirReg;
  volatile uint8_t *_sdaPinReg;
  volatile uint8_t *_sclPinReg;

  uint8_t _transmission;      // transmission status, returned by endTransmission(). 0 is no error.
  uint16_t _i2cdelay;         // delay in micro seconds for sda and scl bits.
  boolean _pullups;           // using the internal pullups or not
  boolean _stretch;           // should code handle clock stretching by the slave or not.
  unsigned long _timeout;     // timeout in ms. When waiting for a clock pulse stretch. 2017, Fix issue #6

  uint8_t rxBuf[SOFTWAREWIRE_BUFSIZE];   // buffer inside this class, a buffer per SoftwareWire.
  uint8_t rxBufPut;           // index to rxBuf, just after the last valid byte.
  uint8_t rxBufGet;           // index to rxBuf, the first new to be read byte.

  // private methods

  void i2c_writebit( uint8_t c );
  uint8_t i2c_readbit(void);
  void i2c_init(void);
  boolean i2c_start(void);
  void i2c_repstart(void);
  void i2c_stop(void);
  uint8_t i2c_write(uint8_t c);
  uint8_t i2c_read(boolean ack);
};

#endif // SoftwareWire_h