OBD Feedback

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Born On:
18:03, 22 July 2011 (CDT)
Last Updated:
14:54, 18 August 2011 (CDT)


Connect a microcontroller to the OBD port on my car, allowing me to use the information available (engine RPM, for example) to control the brightness/color of under-dash lighting. Reminds me of my case modding days of yore; useless blinky lights by the bucketful.


I purchased an OBD connector that should allow me to interface with the car computer and easily tap into Vcc from the wiring harness to power the contraption. Initial reading indicated that OBDII signals were modified CAN and I could probably interface using a standard CAN port on any run-of-the-mill uC. Unfortunately I sold my car ('09 Hyundai Accent, which the connector matches for sure) before the project could move forward. I am not sure how universal the OBD connectors are across makes and models, but I'm hoping to be able to use the same connector with my next vehicle.

  • OBD Connector (have)
  • Vehicle (need)
  • Controller w/ CAN hardware (need, just need to pick out a PIC chip with the required hardware)
  • RGB light bar (have)


I'm not 100% sure what diagnostic numbers will be available on the fly, but I'm hoping I can do something like RPM and vehicle speed, where RPM transitions the output color from blue to red, and speed transitions brightness. Honestly, I figured this part would just take some experimentation till I found something aesthetically appealing; once I can read data from the CAN, it should be easy to select arbitrary diagnostic values and mash them into PWM outputs to control the LEDs.


Just about everything! At this point the project is on semi-permanent hiatus pending getting a vehicle, but I figured I would toss up the description to drum up interest if any exists; I wouldn't mind development going forward on someone else's vehicle for the time being if anyone was interested in collaborating.


Some random links with useful information:

OBD specifications

Microchip appnote AN930 for CAN interfaces

OBD interface using world's trampiest uC (it gets around hurf durf)

OBD<->RS-232 bridge chip, would simplify everything