I have been running my custom build HyperCube (controlled by a RAMPS board) with AstroPrint on a Raspberry Pi 1 for years now. Recently I purchased a Raspberry Pi 3 and a HD webcam to run my printer.
I got Astroprint booted and connected to my wifi as well as showing my camera. However no matter what baud rate I use I can not connect to my printer. The Ramps board has a yellow LED which is on as soon as I give the board power and as soon as I click connect it blinks for a minute and then goes out. It does this for every baud rate.
I used my old PI to make sure everything still worked and it connected just fine still.