Modifying an ELM327 OBD2 scanner opens up possibilities for custom applications. This guide outlines the process of accessing the TX and RX pins on an ELM327 for interfacing with a microcontroller like an Arduino.
Disassemble the ELM327 by removing the enclosure sticker and four screws. Carefully remove the circuit board. Mark one side of the OBD2 connector to ensure correct reassembly, although it’s not crucial for this modification.
Locate the TX and RX pins on the ELM327 board using the provided pin-out diagram of the USB bridge chip. Solder two wires to these pins. Exercise caution during soldering to avoid damaging surface-mounted components. A helpful tip is to pre-program the Arduino to send data to the serial monitor with delays. Then, use a jumper cable connected to the Arduino’s TX pin to probe the ELM327 board. Observe flickering LEDs to identify the TX pin; the RX pin location is easily discernible from the provided images.
To prevent interference, disconnect the ELM327’s USB communication with the PC. This can be achieved by cutting the middle two wires of the 4-pin USB connector. This ensures the ELM327 receives power from the PC’s USB port without the PC occupying the serial controller, allowing the Arduino to communicate freely.
After soldering and modifying the USB connection, reassemble the ELM327. Secure the board within the enclosure using tape or alternative methods. This modification allows for utilizing the ELM327 in custom applications where direct access to the TX and RX pins is required.
This modification enables communication between an Arduino and the ELM327, bypassing the standard USB interface. This opens possibilities for projects requiring custom data logging, diagnostics, or control of vehicle systems. Remember to consult vehicle-specific wiring diagrams and protocols before implementing any modifications to ensure compatibility and safety.
