Marlin and Printrboard notes

I needed to update my firmware on my printrboard with a custom version to use my E3D hotend and was very frustrated with the process. I believe the last time I did a firmware upgrade I must have blown away whatever bootloader was actually there, so I ended up needing to use AVRStudio for this. I used the version Printrbot has in their github repo to make it a bit easier. Their version has a bug with the LCD settings, so I commented out the defines related to that.

Uploading a hex file using AVR Studio:
* build the code using the Arduino IDE
* retrieve the hex file from \\AppData\Temp\build
* open AVR Studio and the programmer tool
* attach the programmer to ISP pins, with pin 1 closest to the SD card slot
* set clock rate to 500khz
* in the 'memory' tab select the hex file and program

If you get timeouts it could indicate that the clock speed set on the programmer is much lower than it should be. I encountered this issue, and empirically arrived at the 500khz as the fastest I could communicate with the printrboard (rev D).