Serial com checksun transmissor

tramissor: mandando dois valores

const uint8_t bufferSize = 4;
uint8_t buffer[bufferSize];

setup{
   Serial.begin(115200);
   buffer[0] = 0x7E;

}

loop{

buffer[1] = (valor); //valor 1
buffer[2] =(valor);  // valor 2
buffer[3] = checksum();
Serial.write(buffer, bufferSize);//manda os valores

}

uint8_t checksum(){
  uint8_t result = 0;
  uint16_t sum = 0;
  for(uint8_t i = 0; i < (bufferSize - 1); i++){
    sum += buffer[i];
  }
  result = sum & 0xFF;
  return result;
}