Main hardware features

• Microchip MCP251863T CAN controller
• Screw terminal for direct access to CAN High/Low twisted pair wiring and a common ground reference
  
• Jumper for a standard 120Ω CAN bus termination resistor
  
• Jumper for enabling and disabling transmit input to the transceiver

Interfacing

• Header pins for logic analyzer access to digital CAN signals (TX and RX pins of the transceiver)
• Header pins for oscilloscope access to the analog CAN signals (CAN High/Low, ground)
• TRIG pin for logic analyzer and oscilloscope triggering on programmable CAN events
• Direct GPIO access to CAN RX and TX pins for software error injection
• GPIO control over transceiver low power standby

The Raspberry Pi Pico is designed to be soldered on to a board using the ‘half moon’ edges, leaving header pins free. The other connections are USB (for power and connectivity to a host) and the CAN bus. The 6-pin header is intended for a logic analyzer and oscilloscope to see raw CAN signals, the yellow jumper is for enabling the termination resistor, and the blue jumper enables transmission on the bus (if this is removed then the board is restricted to only listening to the CAN bus, a useful security feature).

Software support

The software support is provided with a MicroPython SDK that has the following APIs:

• CAN API
• CANHack toolkit API
  
• Trigger API for triggering test instruments on CAN errors and CAN frames with a specified ID and payload
• MIN API to communicate with a host PC over a second virtual USB serial port

The CAN API consists of the following Python classes:

• The CAN class provides control and status of the CAN controller
• The CANFrame class encapsulates CAN frames, which are either created in software or by receiving them from the CAN controller hardware
• The CANError class encapsulates CAN error frames, which are created receiving them from the CAN controller hardware
• The CANID class describes a CAN ID: every CAN frame has a CAN ID, but many frames can have the same ID
  
• The CANIDFilter class describes how a CAN controller should identify and accept CAN frames based on their CAN ID
  

The MIN API provides MIN protocol support for reliable communication with a host PC. Some of the CAN API calls use a binary representation to allow items to be carried over MIN.

Resources

• TheHardware Reference Manual (PDF) for the CANPico board (version 01, issue date 2021-04-29, 8 pages) including schematics.
• TheMicroPython SDK Reference Manual (PDF) for the CANPico board (version 01, issue date 2021-04-29, 32 pages). Documents both the MicroPython CAN API and CANHack API.
• The latest firmware (.uf2, release date 2023-03-09). Based on the v1.15 release of MicroPython for the Pico. The source code is released as a patch file for this MicroPython version (see README.txt for details).
• The latest schematics (PDF) and Kicad design(.kicad_pcb) for the CANPico board.
• The canpico.py examples for the CANPico board (the Thonny IDE can be used to put the file on to the Pico file system)
  
• There is a blog post introducing CANHack and a demonstration video (Note that these both use the CANHack MicroPython API but on the STM32-based PyBoard rather than the Raspberry Pi Pico).