J2534 on Linux

The vendors of the Drewtech MongoosePro GM II and the Tactrix OpenPort 2.0 only ship Windows drivers. These two open source drivers make the cables work on Linux:

Each driver is a single C file that builds to one .so. Neither driver needs libusb, a udev rule or root. Both cables show up as a USB serial device (/dev/ttyACM*) through the cdc_acm kernel module that every desktop distro already has.

txlogger finds J2534 drivers on Linux the same way other Linux J2534 apps do: it reads every ~/.passthru/*.json file. Each file names a driver .so. Both drivers install themselves there.

1. Install build tools

You need git, make and a C compiler.

# Debian / Ubuntu
sudo apt install git build-essential

# Fedora
sudo dnf install git make gcc

# Arch
sudo pacman -S git base-devel

2. Get access to the serial port

Your user must be allowed to open /dev/ttyACM*. Add yourself to the serial group, then log out and back in:

sudo usermod -aG dialout $USER   # Debian, Ubuntu, Fedora
sudo usermod -aG uucp $USER      # Arch

Run groups to check that the group was added.

3. Build and install the driver

Drewtech MongoosePro GM II

git clone https://github.com/roffe/libj2534_mongoose
cd libj2534_mongoose
make
make install

Tactrix OpenPort 2.0

git clone https://github.com/roffe/libj2534_openport2
cd libj2534_openport2
make
make install

make install copies the driver and its descriptor into your home directory. It does not need sudo:

~/.passthru/libj2534_mongoose.so    ~/.passthru/mongoose.json
~/.passthru/libj2534_openport2.so   ~/.passthru/openport2.json

You can install both drivers side by side. To update a driver later, run git pull, make and make install again in its folder.

4. Select it in txlogger

Plug in the cable and start txlogger. Open Settings → CAN Adapter and pick the J2534 entry:

• J2534 #0 Drew Technologies MongoosePro GM II
• J2534 #1 Tactrix Inc. OpenPort 2.0

The number depends on how many drivers you have installed.

The Linux AppImage includes J2534 support. If you build txlogger from source, make in the txlogger repo already builds with the j2534 tag.

Adapter notes

MongoosePro GM II

• The cable needs power from the car. It will not open without battery voltage on OBD pin 16. You get no voltage on the vehicle connector otherwise.
• The driver uses the first Drew/Mongoose device under /dev/serial/by-id/. To pick a specific port, start txlogger with MONGOOSE_PORT=/dev/ttyACM1 ./txlogger.
• It does not work with Trionic 5. At T5’s 615 kbit/s the cable sends frames but never passes received frames back. The firmware causes this, and the driver cannot fix it.

OpenPort 2.0

• Remove the microSD card. With a card inserted the OpenPort can start in standalone logging mode, and then it never shows up as a USB device.

• Set OP2_J2534_LOG to trace every command and reply. Include this trace when you report a bug:

  OP2_J2534_LOG=/tmp/op2.log ./txlogger
  

• The OpenPort repo has a small test program that prints the firmware version and battery voltage without starting txlogger:

  make test_op2
  ./test_op2
  

Troubleshooting

No J2534 entry in the adapter list. Check that ~/.passthru/ has both the .so and the .json file. txlogger skips a .json whose .so is missing.

Permission denied on /dev/ttyACM0. You are not in the dialout/uucp group yet, or you have not logged out and back in since adding it.

Nothing under /dev/ttyACM*. Run sudo dmesg | tail right after plugging in the cable. You should see a cdc_acm line. If you do not, check the cable, the USB port and, on the OpenPort, the microSD card.