Additionally, I can do Serial.readBytes() after there's nothing left (or rather, there shouldn't be any bytes left.) and it will give me some bytes, but they're total garbage. Similarly, Serial.available() seems sort of broken in that it tells me there are no bytes to read (returns 0), but then I can read the bytes I'm expecting with Serial.readBytes(). but then Serial.readBytes() gives me the byte stream I was expecting from the buffer! What's going on here? If I do Serial.read() just prior to Serial.readBytes(), it comes back with -1, meaning no bytes to read. However I don't understand the difference between Serial.readBytes() and Serial.read(). I'm also reading back what I originally sent (first) as well as the response (second), since I have Tx1 and Rx1 tied together (required in my setup because this servo only has one data wire). I've actually gotten it to work pretty well if I use Serial1.readBytes(), specifying the length of the buffer (number of bytes I'm expecting). Basically I construct some byte arrays as instructions, send them over to the servo (with Serial1.write()), and then read back a reply. I'm trying to do some fairly simple serial communication and have things partially working, but am pretty confused about a couple results I'm getting.įor a little background, I'm using an Arduino Mega 2560 to try to communicate with a Dynamixel servo (MX-64) over TTL (half-duplex, asynchronous) with Tx1 and Rx1.

Arduino mega serial port numbering