I did 2 things.
1. I flashed the HID bootloader (included in package below, you need to use the icsp header on the Printrboard and an ISP programmer (I used an Arduino Mega 2560 I had from a RAMPS setup)
2. Installed Arduino 1.6.8 and used the package from here: https://github.com/scwimbush/Printrboard-HID-Arduino-IDE-Support
Flash of Marlin from Arduino IDE only works on Windows with that package, the binary for the uploader isn't there for MAC
1. I flashed the HID bootloader (included in package below, you need to use the icsp header on the Printrboard and an ISP programmer (I used an Arduino Mega 2560 I had from a RAMPS setup)
2. Installed Arduino 1.6.8 and used the package from here: https://github.com/scwimbush/Printrboard-HID-Arduino-IDE-Support
Flash of Marlin from Arduino IDE only works on Windows with that package, the binary for the uploader isn't there for MAC