I've been working on the firmware for the past week, but I decided to get started on custom hardware for the project. Up until now, I've been using the Tiva C Series Launchpad from TI with a hacked together add-on board for CAN. It's time for custom hardware.
This hardware uses the same microcontroller family, but opts for a model with 128k of flash instead of the 256k on the Launchpad. Since 128k should be plenty, this will lower the BOM cost of the hardware.
There is room for four CAN transceivers on board. However, it is intended to only be populated with two at a time. This way, you can choose between two high-speed buses, two single-wire buses, or one of each. For the high speed buses, there's a termination resistor that can be enabled with a jumper.
The hardware is fairly simple, and the next step is to design the PCB. That should get done shortly.
The schematic is hosted on Github, and available as a PDF here. It's a draft, let me know if you spot any issues!