Connecting your ELM327 OBD2 scanner to a USB port requires understanding its wiring. This guide provides a detailed wiring diagram and step-by-step instructions to help you successfully connect your ELM327 to your computer.
Understanding the ELM327 OBD2 to USB Connection
The ELM327 OBD2 scanner relies on specific TX (transmit) and RX (receive) pins for communication with a computer via a USB connection. These pins allow data to flow between the scanner and diagnostic software. A USB-to-serial converter chip on the ELM327 board facilitates this communication.
Accessing the ELM327 Circuit Board
Carefully remove the sticker and the four screws on the ELM327 enclosure using a small star screwdriver. Gently take out the circuit board. Before disconnecting any connectors, mark the orientation of the OBD2 connector to ensure correct reassembly. While not essential for this specific modification, knowing the connector’s orientation is always beneficial.
Identifying TX and RX Pins
Locate the USB bridge chip on the circuit board. Refer to the chip’s datasheet or online resources to identify the TX and RX pins. Common chips used include the CH340 and CP2102. Their datasheets provide detailed pinout information. Once identified, carefully solder two wires to the TX and RX pins. Precision is crucial to avoid damaging surrounding components.
Verifying Pin Identification
To confirm correct pin identification, you can use an Arduino programmed to send data to its serial monitor. Connect a jumper cable to the Arduino’s TX pin and touch the other end to various points on the ELM327 board. Observe for flickering LEDs or serial activity on the Arduino’s monitor, indicating successful communication. This method helps pinpoint the TX pin. The RX pin is usually located adjacent to the TX pin.
Isolating the USB Connection
The ELM327 board usually has a 4-pin connector for the USB cable. To prevent the PC from directly communicating with the ELM327 and potentially interfering with the Arduino connection, cut the middle two wires of this connector. This ensures that the USB connection only provides power, allowing the Arduino to communicate with the ELM327 through the soldered wires.
Reassembling the ELM327
After soldering and isolating the USB connection, carefully place the circuit board back into its enclosure. Secure it with tape or screws. Your ELM327 is now ready to connect to your computer via the soldered wires and an external USB-to-serial adapter connected to the Arduino.
Conclusion
By following these steps and referring to the wiring diagram, you can successfully connect your ELM327 OBD2 scanner to your computer using a USB connection. This modification enables various diagnostic and data logging applications using an Arduino or similar microcontroller. Remember to exercise caution while soldering and consult datasheets for accurate pin identification.
