Method writeBitsW

lib/i2cdev/I2Cdev.cpp:530–549

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) */

 * @return Status of operation (true = success)
 */
bool I2Cdev::writeBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t data, void *wireObj) {
    //              010 value to write
    // fedcba9876543210 bit numbers
    //    xxx           args: bitStart=12, length=3
    // 0001110000000000 mask word
    // 1010111110010110 original value (sample)
    // 1010001110010110 original & ~mask
    // 1010101110010110 masked | value
    uint16_t w;
    if (readWord(devAddr, regAddr, &w, I2Cdev::readTimeout, wireObj) != 0) {
        uint16_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, wireObj);
    } else {
        return false;
    }
}

/** Write single byte to an 8-bit device register.
 * @param devAddr I2C slave device address