@nexus1212 You're using a 3V Arduino. It looks like all the patterns are correct, but it's just not getting things right. A lot of the unprintable characters in ASCII are at the start of the table, so I'm thinking maybe you have a serial connection that is expecting 5V as the 'high' voltage and what it's actually seeing is so borderline that it's not always registering correctly. So look if there's a setting on whatever you're using to read the serial data to set it to be 3V compatible. (Maybe a physical jumper on the board?) It's so close to getting it that I bet it's something super simple like that and your Arduino is really doing it's job pretty well.