i2c.h

Go to the documentation of this file.

/*
 * atMETEO - An ATmega based weather station
 * Copyright (C) 2014-2015 Christian Fetzer
 *
 * This program 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 of the License, or
 * (at your option) 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.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#pragma once

#include <inttypes.h>  // AVR toolchain doesn't offer cinttypes header

#ifndef F_CPU
#error "F_CPU not defined for i2c.h"
#endif

extern "C" {
    #include <external/i2cmaster/i2cmaster.h>
}

namespace Avr
{

class I2c
{
public:
    static I2c& instance()
    {
        return s_instance;
    }

    void beginTransmission(uint8_t address)
    {
        m_bufferIndex = 0;

        i2c_start((address << 1) | I2C_WRITE);
    }

    void write(uint8_t byte)
    {
        if (m_bufferIndex == c_bufferSize)
            return;

        m_buffer[m_bufferIndex++] = byte;
    }

    void endTransmission(bool stop = true)
    {
        for (uint8_t index = 0; index < m_bufferIndex; ++index) {
            if (i2c_write(m_buffer[index]) != 0)
                return;
        }

        if (stop)
            i2c_stop();
    }

    uint8_t requestFrom(uint8_t address, uint8_t quantity, bool stop = true)
    {
        quantity = Sensors::min(quantity, c_bufferSize);
        if (quantity == 0)
            return 0;

        if (i2c_start((address << 1) | I2C_READ) != 0)
            return 0;

        m_bufferIndex = 0;
        while (--quantity > 0) {
            m_buffer[m_bufferIndex++] = i2c_readAck();
        }
        m_buffer[m_bufferIndex++] = i2c_readNak();
        m_bufferReadIndex = 0;

        if (stop)
            i2c_stop();

        return m_bufferIndex;
    }

    uint8_t read()
    {
        if (m_bufferReadIndex == m_bufferIndex)
            return 0;

        return m_buffer[m_bufferReadIndex++];
    }

private:
    static I2c s_instance;

    static const uint8_t c_bufferSize = 8;
    uint8_t m_buffer[c_bufferSize];
    uint8_t m_bufferIndex = 0;
    uint8_t m_bufferReadIndex = 0;

    I2c()
    {
        i2c_init();
    }
};

I2c I2c::s_instance = I2c();
  // \addtogroup libtarget_i2c

}  // namespace Avr