demo.ino

void recv()
{
  while (Serial3.available() > 0)
  {
    for (byte index = 0; index < MAXLENGTH - 1; index++)
    {
      receivedCommandStack[index] = receivedCommandStack[index + 1];
    }
    receivedCommandStack[MAXLENGTH - 1] = Serial3.read();

    if ((receivedCommandStack[0] == 0xFF) && (receivedCommandStack[1] == 0x17) && (receivedCommandStack[2] == 0x00) && (receivedCommandStack[3] == 0x00)) //head bit and sum are all right
    {
      uint8_t vPin = receivedCommandStack[4];
      uint8_t value = receivedCommandStack[5];
      Blynk.virtualWrite(vPin, value);
    }
  }
}