CAN Bus

I got my ELM usb adapter from SECONS in Prague, around 100 years ago.

http://www.obd-2.com/ See also tenrec not 8track, which has been gone for a decade.

2022-12-10 back looking at this, at least a hundred years have elapsed (Linux time) since I started this page.

CAN interfaces

Raspberry Pi

2024-09-25 I unpacked these 2 Waveshare Pi hats today. They both have handy features like jumpers or dip switches to select termination and TVS protection.

Waveshare RS485 CAN HAT (Pi Zero footprint) Includes both MCP2515 and MAX485 transceivers; I don't have a use for RS485 at the moment.

Waveshare 2-channel CAN HAT (full size Pi footprint) Includes 2 MCP2515 transceivers, so you can do loop back testing, handy. Or put one on the instrumentation bus and one on the OBD II port? Here is an article that uses one. https://circuitcellar.com/research-design-hub/projects/building-a-drop-in-automotive-hmi/

Waveshare has a CAN FD board too, but I don't think I need that right now.

Open hardware Pi CAN Board Controller Area Network based on the MCP2515 controller.

WICAN from Meat Pi, based on the ESP32C3, here is their github page. https://github.com/meatpiHQ/wican-fw

Grove

See Grove.

SEEED Studio CAN-BUS module and the ODB II CAN BUS development kit, each about about $20

https://www.seeedstudio.com/blog/2019/11/27/introduction-to-can-bus-and-how-to-use-it-with-arduino/

There is a newer Seeed Studio "Serial CAN FD module", $4.90, I bought two, from Digikey. See https://docs.longan-labs.cc/114992978/ It has its own MCU, it's a GD32E103 which is based on the ARM Cortex M4. (Of course)

Other

https://www.hackster.io/kenliao/vehicle-gui-can-bus-display-05fb45

Sparkfun UBM32 controller: USB 32-Bit Whacker - PIC32MX795 Development Board $40

Software

https://github.com/nopnop2002/esp-idf-CANBus-Monitor There is an ESP32-C3 version too.

Dashboards

"RealDash" looks like it might be fun. It runs on Android, maybe I could use an old phone or tablet. I have enough of those now.

Circuit Cellar article: eDash Robin Brophy Sep 2011 issue 254 downloadable here (but outdated) https://www.scantool.net/scantool/downloads/116/edash-microobd_200.pdf

Connecting

I got an OBD-2 extension cable with 90 degree ends to make a low profile connection. I cut the cable in half. (Photo!) Now I have a connector with a 12" cable ready to use.

Termination

https://electronics.stackexchange.com/questions/470382/can-bus-termination-resistors-for-can-logger-device

I don't need termination as long as my cable is less than 0.5m long. (It was 18" but I snipped it down to be on the safe side.)

Pinouts

OBD2 pinouts

Signals that matter to me, and the wire colors:

5 signal ground -- orange

6 CANH -- Black

14 CANL -- Green

16 12V always on -- Brown

https://www.14core.com/wiring-the-mcp2515-shield-with-obd-on-arduino/ connector info

https://www.14core.com/wiring-the-mcp2515-controller-area-network-can-bus-diagnostics/

Interfaces

MCP2515

I intend trying the MCP2515 chip first because it's commonly used. Microchip MCP2515 datasheet

I got this breakout board: Seeed Xiao https://www.seeedstudio.com/Seeed-Studio-CAN-Bus-Breakout-Board-for-XIAO-and-QT-Py-p-5702.html

I got two, so one will have a 6 pin header soldered to the SPI connector and the other will have a Xiao ESP32C6 installed.

Seeed's board uses the TI SN65HVD23x 3.3-V CAN Bus Transceiver so it's all 3v3 and that means it can work with a Pi. Some older boards use 5V transceivers.

https://github.com/kvba1/ESP32-MCP2515-OBD2-CANBUS ESP32 + MC2515

https://github.com/yogiD/MCP2515-OBD Arduino + MCP2515

GD32E103CA

Seed + Grove from Longan Labs https://github.com/Longan-Labs/Serial_CAN_FD_Module

This board has a UART on its Grove port, so in theory Pi + Grove and I should be able to see it on a serial console. Right? Easy easy easy?? Then use AT commands to confirm it functions.

Since I have a RP2040 + Grove set up already I am going there first. Raspberry_Pi_RP2040

ICSIM on Raspberry Pi

ICSIM = Instrument Cluster Simulator = test CAN bus without breaking your car. Also, you can do bench testing!

https://github.com/zombieCraig/ICSim

Software

Starting from Bookworm on a Pi 5

 sudo apt-get install libsdl2-dev libsdl2-image-dev can-utils

Hardware

SPI to Pi

Xiao MCP2515 module: This article is a close match for what I am doing. Adding CAN controller to Raspberry Pi I only bought one, grrr.

It would be easier to connect the GD32 board since it's Grove, but I'd need software for that.

Resources

https://copperhilltech.com/ Pi and Arduino boards for CAN bus, OBD-2, NMEA, etc

Learn about CAN Bus from SEEED

Call it car hacking or CAN hacking https://illmatics.com/carhacking.html

https://medium.com/@yogeshojha/car-hacking-101-practical-guide-to-exploiting-can-bus-using-instrument-cluster-simulator-part-i-cd88d3eb4a53

Elm Electronics the folks who make the interface.

OBDtester and pyOBD

OBD Auto Doctor Free and paid versions, including Linux. The paid version is $20 per year.

Python

There are around 700 forks of pyobd... the one that shows up in pypi.org I think appears to be Brendan Whitfield's.

This one looks interesting too though. barracuda-fsh / pyobd

Wikipedia knowledge

OBDuino
OBD-II PIDs