So maybe I confused it needlessly. Just ignore the rPi in your "UPGRADE" it simply isn't important to this discussion. There are tons of RAMPS compatible boards, you have to make sure your configuration of Marlin matches the board you are planning to use. Just look at this list; https://github.com/MarlinFirmware/Marlin/wiki/Supported-Hardware. You need to make sure your board is configure for the right hardware. I suggested you compare it to the Robo configuration so you have the correct sensors on the right pins and you mimic the actual working of the R2. Things like where the endstops are located, where it homes, etc. Robo did not use all the Marlin defaults so you have to match those by making changes to the default configuration. Clear as mud, isn't it.