That y umlaut is most likely the way your serial monitor renders 255 (-1). It's what the serial read command returns when there is nothing to read. Use serial.available to check that there is actually something to read before you do so.
That y umlaut is most likely the way your serial monitor renders 255 (-1). It's what the serial read command returns when there is nothing to read. Use serial.available to check that there is actually something to read before you do so.