Julien Vanier created this CAN bus simulator on the Raspberry Pi to help develop and test the Carloop open-source car adapter:

CAN Simulator

used to transmit and receive messages simulating OBD-II communications and regular vehicle messages

The simulator consists of:

• MCP2515 standalone CAN controller connects to Raspberry Pi over the SPI bus
• TJA1049 CAN transceiver translate logic levels for high speed CAN
• 5V to 12V step up regulator to provide 12V on ODB connector
• Off-the-shelf OBD cable and connector
• Simulator program on the Raspberry Pi

jvanier shared the board on OSH Park:

CAN-Simulator v1