CAN Monitoring (ELM327)

This program reads CAN frames from an ELM327 / ELM329 chip (widely available) and makes them available through:

• a WebSocket server (JSON format),
• a CAN-ETH output (that is CAN over UDP),
• a Wireshark-compatible libpcap file.

Features

• A simplistic Web interface showing the last frame for each identifier
  
• Customizable "sequence", which is the startup configuration (overridable on the Web interface)
• Automatic recover from most possible communication errors
• Allows any supported serial port baudrate (AT BRD command)
• Configuration is live-refreshed (no restart needed)
• Multiple instances allowed using different parameters files (allowing different CAN buses simultaneously)
• Possibility to run multiple HTTP servers for better performance
• Nice console output to easily debug problems
• Optional libpcap SocketCAN logging of received CAN frames

Requirements

• An OBD scanner featuring an ELM327 / ELM329 chip (preferably connected through bare RS-232 or USB converter)
• Python 3.6 or greater, extended to Python 3.4.4
• pySerial 3.0.1 or greater
• An OS supported by pySerial

Instructions

1. Install Python3.
2. Install pySerial.
3. Edit the files parameters.py and sequenceELM327_CAN.py in the sub-directory config.
4. When you are ready to start, run main.py.

Extra information

• The default web interface is available at http://127.0.0.1:18327/show_dataframes.htm
• Command line arguments:
  • "--parameters=<file>" Override the parameters file (relative to config or absolute).
  • "--sequence=<file>" Override the sequence file (relative to config or absolute).

Known problems

• I receive BUFFER FULL alerts frequently!
  • You should try to increase the serial port baudrate.
  • If it is not enough, try to play with the hardware CAN filter (or the CAN whitelist that will set it up automatically) to reduce the amount of data.
• I receive invalid CAN frames and empty lines randomly!
  • pySerial seems to produce a huge CPU usage on Windows. When the receive buffer of the serial port overflows, some data gets flushed and to the program the lost bytes have never existed: at this point the line of data is like the beginning of a frame and the end of another. So most often this produces an invalid CAN frame representation, but sometimes a weird valid frame that never existed shows up.
  • You can try to reduce the amount of data (solution below).
  • You can increase the process priority in the task manager.
  • Note that under such conditions, CAN frames are lost and the latency of CAN readings is increased.

Support

You can open an issue when you have a question, or you can join my Discord server Yvon à bord ! where you are very welcome, or see my contact details on my GitHub profile.