File content as of revision 2:f8bfb37b2e1f:

// ported from arduino library: https://github.com/jrowberg/i2cdevlib
// written by szymon gaertig (email: szymon@gaertig.com.pl, website: szymongaertig.pl)
// Changelog:
// 2013-01-08 - first release

#include "I2Cdev.h"

#define useDebugSerial

I2Cdev::I2Cdev(): i2c(I2C_SDA,I2C_SCL), debugSerial(USBTX, USBRX)
{

}

I2Cdev::I2Cdev(PinName i2cSda, PinName i2cScl): i2c(i2cSda,i2cScl), debugSerial(USBTX, USBRX)
{

}

/** Read a single bit from an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to read from
 * @param bitNum Bit position to read (0-7)
 * @param data Container for single bit value
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Status of read operation (true = success)
 */
int8_t I2Cdev::readBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t *data, uint16_t timeout) {
    uint8_t b;
    uint8_t count = readByte(devAddr, regAddr, &b, timeout);
    *data = b & (1 << bitNum);
    return count;
}

/** Read a single bit from a 16-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to read from
 * @param bitNum Bit position to read (0-15)
 * @param data Container for single bit value
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Status of read operation (true = success)
 */
int8_t I2Cdev::readBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t *data, uint16_t timeout) {
    uint16_t b;
    uint8_t count = readWord(devAddr, regAddr, &b, timeout);
    *data = b & (1 << bitNum);
    return count;
}

/** Read multiple bits from an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to read from
 * @param bitStart First bit position to read (0-7)
 * @param length Number of bits to read (not more than 8)
 * @param data Container for right-aligned value (i.e. '101' read from any bitStart position will equal 0x05)
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Status of read operation (true = success)
 */
int8_t I2Cdev::readBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t *data, uint16_t timeout) {
    // 01101001 read byte
    // 76543210 bit numbers
    //    xxx   args: bitStart=4, length=3
    //    010   masked
    //   -> 010 shifted
    uint8_t count, b;
    if ((count = readByte(devAddr, regAddr, &b, timeout)) != 0) {
        uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
        b &= mask;
        b >>= (bitStart - length + 1);
        *data = b;
    }
    return count;
}

/** Read multiple bits from a 16-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to read from
 * @param bitStart First bit position to read (0-15)
 * @param length Number of bits to read (not more than 16)
 * @param data Container for right-aligned value (i.e. '101' read from any bitStart position will equal 0x05)
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Status of read operation (1 = success, 0 = failure, -1 = timeout)
 */
int8_t I2Cdev::readBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t *data, uint16_t timeout) {
    // 1101011001101001 read byte
    // fedcba9876543210 bit numbers
    //    xxx           args: bitStart=12, length=3
    //    010           masked
    //           -> 010 shifted
    uint8_t count;
    uint16_t w;
    if ((count = readWord(devAddr, regAddr, &w, timeout)) != 0) {
        uint16_t mask = ((1 << length) - 1) << (bitStart - length + 1);
        w &= mask;
        w >>= (bitStart - length + 1);
        *data = w;
    }
    return count;
}
/** Read single byte from an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to read from
 * @param data Container for byte value read from device
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Status of read operation (true = success)
 */
int8_t I2Cdev::readByte(uint8_t devAddr, uint8_t regAddr, uint8_t *data, uint16_t timeout) {
    return readBytes(devAddr, regAddr, 1, data, timeout);
}

/** Read single word from a 16-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to read from
 * @param data Container for word value read from device
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Status of read operation (true = success)
 */
int8_t I2Cdev::readWord(uint8_t devAddr, uint8_t regAddr, uint16_t *data, uint16_t timeout) {
    return readWords(devAddr, regAddr, 1, data, timeout);
}

/** Read multiple bytes from an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr First register regAddr to read from
 * @param length Number of bytes to read
 * @param data Buffer to store read data in
 * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
 * @return Number of bytes read (-1 indicates failure)
 */
int8_t I2Cdev::readBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t *data, uint16_t timeout)
{
    char command[1];
    command[0] = regAddr;
    char *redData = (char*)malloc(length);
    i2c.write(devAddr<<1, command, 1, true);
    i2c.read(devAddr<<1, redData, length);
    for(int i =0; i < length; i++) {
        data[i] = redData[i];
    }
    free (redData);
    return length;
}

int8_t I2Cdev::readWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t *data, uint16_t timeout)
{
    return 0;
}

/** write a single bit in an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to write to
 * @param bitNum Bit position to write (0-7)
 * @param value New bit value to write
 * @return Status of operation (true = success)
 */
bool I2Cdev::writeBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t data) {
    uint8_t b;
    readByte(devAddr, regAddr, &b);
    b = (data != 0) ? (b | (1 << bitNum)) : (b & ~(1 << bitNum));
    return writeByte(devAddr, regAddr, b);
}

/** write a single bit in a 16-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to write to
 * @param bitNum Bit position to write (0-15)
 * @param value New bit value to write
 * @return Status of operation (true = success)
 */
bool I2Cdev::writeBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t data) {
    uint16_t w;
    readWord(devAddr, regAddr, &w);
    w = (data != 0) ? (w | (1 << bitNum)) : (w & ~(1 << bitNum));
    return writeWord(devAddr, regAddr, w);
}

/** Write multiple bits in an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to write to
 * @param bitStart First bit position to write (0-7)
 * @param length Number of bits to write (not more than 8)
 * @param data Right-aligned value to write
 * @return Status of operation (true = success)
 */
bool I2Cdev::writeBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t data) {
    //      010 value to write
    // 76543210 bit numbers
    //    xxx   args: bitStart=4, length=3
    // 00011100 mask byte
    // 10101111 original value (sample)
    // 10100011 original & ~mask
    // 10101011 masked | value
    uint8_t b;
    if (readByte(devAddr, regAddr, &b) != 0) {
        uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
        data <<= (bitStart - length + 1); // shift data into correct position
        data &= mask; // zero all non-important bits in data
        b &= ~(mask); // zero all important bits in existing byte
        b |= data; // combine data with existing byte
        return writeByte(devAddr, regAddr, b);
    } else {
        return false;
    }
}

/** Write multiple bits in a 16-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register regAddr to write to
 * @param bitStart First bit position to write (0-15)
 * @param length Number of bits to write (not more than 16)
 * @param data Right-aligned value to write
 * @return Status of operation (true = success)
 */
bool I2Cdev::writeBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t data) {
    //              010 value to write
    // fedcba9876543210 bit numbers
    //    xxx           args: bitStart=12, length=3
    // 0001110000000000 mask byte
    // 1010111110010110 original value (sample)
    // 1010001110010110 original & ~mask
    // 1010101110010110 masked | value
    uint16_t w;
    if (readWord(devAddr, regAddr, &w) != 0) {
        uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
        data <<= (bitStart - length + 1); // shift data into correct position
        data &= mask; // zero all non-important bits in data
        w &= ~(mask); // zero all important bits in existing word
        w |= data; // combine data with existing word
        return writeWord(devAddr, regAddr, w);
    } else {
        return false;
    }
}

/** Write single byte to an 8-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register address to write to
 * @param data New byte value to write
 * @return Status of operation (true = success)
 */
bool I2Cdev::writeByte(uint8_t devAddr, uint8_t regAddr, uint8_t data) {
    return writeBytes(devAddr, regAddr, 1, &data);
}

/** Write single word to a 16-bit device register.
 * @param devAddr I2C slave device address
 * @param regAddr Register address to write to
 * @param data New word value to write
 * @return Status of operation (true = success)
 */
bool I2Cdev::writeWord(uint8_t devAddr, uint8_t regAddr, uint16_t data) {
    return writeWords(devAddr, regAddr, 1, &data);
}

bool I2Cdev::writeBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t *data)
{
    i2c.start();
    i2c.write(devAddr<<1);
    i2c.write(regAddr);
    for(int i = 0; i < length; i++) {
        i2c.write(data[i]);
    }
    i2c.stop();
    return true;
}

bool I2Cdev::writeWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t *data)
{
    return true;
}

uint16_t I2Cdev::readTimeout(void)
{
    return 0;
}