Wire.h

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/*
  TwoWire.h - TWI/I2C library for Arduino & Wiring
  Copyright (c) 2006 Nicholas Zambetti.  All right 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
 
  Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts
  Modified December 2014 by Ivan Grokhotkov (ivan@esp8266.com) - esp8266 support
  Modified April 2015 by Hrsto Gochkov (ficeto@ficeto.com) - alternative esp8266 support
*/
 
#pragma once
 
#include <Stream.h>
#include <twi_arch.h>
 
class TwoWire : public Stream
{
public:
    static constexpr size_t BUFFER_LENGTH{32};
 
    enum Status {
        I2C_OK = 0,
        I2C_SCL_HELD_LOW = 1,
        I2C_SCL_HELD_LOW_AFTER_READ = 2,
        I2C_SDA_HELD_LOW = 3,
        I2C_SDA_HELD_LOW_AFTER_INIT = 4,
    };
 
    enum Error {
        I2C_ERR_SUCCESS = 0,
        I2C_ERR_ADDR_NACK = 2,
        I2C_ERR_DATA_NACK = 3,
        I2C_ERR_LINE_BUSY = 4,
    };
 
    using UserRequest = void (*)();
    using UserReceive = void (*)(int len);
 
    TwoWire() : Stream()
    {
    }
 
    void begin(uint8_t sda, uint8_t scl);
 
    void pins(uint8_t sda, uint8_t scl);
 
    void begin();
 
    void end();
 
    void setClock(uint32_t frequency);
 
    void setClockStretchLimit(uint32_t limit);
 
    void beginTransmission(uint8_t address);
 
    Error endTransmission(bool sendStop = true);
 
    uint8_t requestFrom(uint8_t address, uint8_t size, bool sendStop = true);
 
    Status status();
 
    /* Stream methods */
 
    size_t write(uint8_t) override;
    size_t write(const uint8_t*, size_t) override;
    int available() override;
    int read() override;
    int peek() override;
    void flush() override;
 
    using Print::write;
 
    // Slave mode not currently implemented
    void onReceive([[maybe_unused]] UserReceive callback)
    {
        // userReceiveCallback = callback;
    }
 
    // Slave mode not currently implemented
    void onRequest([[maybe_unused]] UserRequest callback)
    {
        // userRequestCallback = callback;
    }
 
private:
    uint8_t twi_sda{DEFAULT_SDA_PIN};
    uint8_t twi_scl{DEFAULT_SCL_PIN};
    uint8_t twi_dcount{18};
    unsigned twi_clockStretchLimit{0};
 
    uint8_t rxBuffer[BUFFER_LENGTH]{};
    uint8_t rxBufferIndex{0};
    uint8_t rxBufferLength{0};
 
    uint8_t txAddress{0};
    uint8_t txBuffer[BUFFER_LENGTH]{};
    uint8_t txBufferIndex{0};
    uint8_t txBufferLength{0};
 
    bool transmitting{false};
    UserRequest userRequestCallback{nullptr};
    UserReceive userReceiveCallback{nullptr};
 
    void twi_delay(uint8_t v);
    bool twi_write_start();
    bool twi_write_stop();
    bool twi_write_bit(bool bit);
    bool twi_read_bit();
    bool twi_write_byte(uint8_t byte);
    uint8_t twi_read_byte(bool nack);
    Error twi_writeTo(uint8_t address, const uint8_t* buf, size_t len, bool sendStop);
    Error twi_readFrom(uint8_t address, uint8_t* buf, size_t len, bool sendStop);
};
 
#if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_TWOWIRE)
extern TwoWire Wire;
#endif