Arduino sending data with checksum CRC16

The best way to reset it is here:

void command(String value) {
  memset(serialBuffer, 0, sizeof serialBuffer);
  crc = 0;
  sendToI2CUART(serialBuffer, value);
}

I do not see what you mean with the c-string? I will put the characters from the command in the serialBuffer array. Is there automatically a '\0' termination because of the String declaration?