nabil.me

Update: Here is the GitHub repo

A couple of weeks ago, my dad and I were troubleshooting the cause of a check engine light on our 2000 Toyota Camry. Using an off-the-shelf OBD-II reader, we got a warning about the EGR system. After trying every test in the book, we came up empty and had to take it to Toyota. They found a sticky relay that was beginning to fail — a tricky issue to catch since the light only came on after ~30 km of driving. If we had a way to monitor signals in real time, this problem might have been easier to solve.

That’s why I created my OBD-II board.

The board is essentially the reference schematic for the STN1110, which converts various OBD-II physical layers into RS232. The bottom of the board includes a Bluetooth module from DealExtreme. The goal is to connect it to a smartphone or tablet to log data wirelessly.

Similar products exist, but I couldn’t find any affordable ones that use the STN1110. Scantool offers a 3.3cm × 1.5cm module for $70 — a bit pricey for a $10 chip.

Scantool's module

The STN1110 is supposedly faster than the Elm327, making it great for real-time data logging. It supports the following protocols:

• SAE J1850 PWM
• SAE J1850 VPW
• SAE J1939
• ISO 9141-2
• ISO 14230-4 (KWP 2000)
• ISO 15765-4 (CAN)
• ISO 11898 (raw CAN)

My board is 5cm × 5cm, which means it can be manufactured through Seeed Studio for just $10. I’ll post the schematics on GitHub in the next couple of days.