Two OS-DBTC documents (updated) “BlueTrain IF Manual.rtf” and (new) “BlueTrain PIC Dev HW.rtf” are available to anybody for download at: sourceforge.net/projects/dbtc/files/BlueTrain/.
The “HW” document is intended for use as an input into the design/development of OS-DBTC-mobile-decoder-boards. The processor could also be a PIC18F46K22, and the DRV8801-chip could be a full-wave-PWM-motor-circuit. Most of the simple PIC I/O can be move to different PIC-pins to minimize the board size. The HC05-Bluetooth-sub-board would typically be mounted on the non-component side of the decoder-board with the Bluetooth-antenna protruding over the edge.