I’m playing with a test program, it;s not doing what I want. (Please wait.) I think the difference between readBytesUntil and readStringUntil is only the type of var that it writes to. I’m convinced by this that strings are evil, and they didn’t exist when I learned C. I meant that you don’t need to use Serial.available()>0 because you can call readBytesUntil repeatedly and detect success from it’s return value.