This guide outlines the process of connecting an ESP8266 to an ELM327 OBDII reader to create a custom display. This allows for a dedicated screen to view vehicle data without relying on a laptop or smartphone.
Accessing the ELM327 Board
Begin by removing the sticker and the four screws on the ELM327 cable enclosure using a small star screwdriver. Carefully remove the circuit board.
Identifying TX and RX Pins
Locate the TX (Transmit) and RX (Receive) pins on the ELM327 board. Refer to the USB bridge chip’s pinout diagram for precise identification. A common chip used is the CH340.
Soldering Connection Wires
Carefully solder two wires to the TX and RX pins. Exercise caution to avoid damaging surrounding components. If unsure, use a multimeter in continuity mode to confirm pin identification.
Testing the Connection
To verify the connection, program an Arduino to send data to the serial monitor with short delays. Connect a jumper wire to the Arduino’s TX pin and probe the ELM327 board’s RX pin. Observe for flickering LEDs, indicating successful communication. This process helps confirm the correct RX pin.
Isolating the USB Connection
For dedicated communication with the ESP8266, isolate the ELM327’s USB connection to the PC. This can be achieved by carefully cutting the middle two wires of the 4-pin USB connector. This ensures the ELM327 receives power but prevents data interference from the PC.
Reassembly
Once the wires are soldered and the USB connection modified, reassemble the ELM327. Secure the board within the enclosure. If the original enclosure is unsuitable for your application, consider alternative housing options.
Connecting to ESP8266
Connect the wires from the ELM327 to the ESP8266’s RX and TX pins, remembering to cross the connections (ELM327 TX to ESP8266 RX, and vice versa). Power the ESP8266 and upload a sketch designed to read OBDII data from the serial connection and display it on a connected screen.
This modification allows for a standalone OBDII reader with a custom display powered by an ESP8266. Remember to exercise caution when soldering and modifying electronics.
