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Replace_ELM327_HC04_Firmware.md

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Replace ELM327 firmware

This document describes how to replace ELM327 adapter firmware

Hardware Requirements:

  • ELM327 adapter with PIC18F25K80 chip. For the best models to buy from aliexpress, search PIC18F25K80 ELM37 and refer to #39
  • PICkit 3 or 4 programmer
  • 12V power supply to power ELM327 adapter via OBD2 connector

ELM327 board connections:

ELM327 HC04

From left to right: MCLR (orange), 5V (green), GND (yellow), PGD (purple), PGC (blue)

Step1: Get the needed software:

Option 1 (Recommended):

  1. Download MPLAB X IDE and install it, start MPLAB X IPE and select device PIC18F25K80.
  2. Go to the Step2.

Option 2:

  1. Download and install the PICkit™ 3 Programming App and Scripting Tool v3.10
  2. Edit the PICkit3.ini in the folder where the tool has been installed and add the following lines to the end of it:
TMEN:
REVS: Y
  1. Download the File PKPlusDeviceFile.dat from https://sourceforge.net/projects/pickit3plus/
  2. Delete original PK2DeviceFile.dat in the tool folder, and rename PKPlusDeviceFile.dat to PK2DeviceFile.dat
  3. Start PICkit 3 v3.01

Step2: Program PIC18F25K80

  • Connect your PICkit 3/4 to the test points on the board of ELM327 adapter (see photo above)
  • Connect 12V (pin 16) and GND (pin 4) from power supply to ELM327 ODB2 connector: https://www.obd-2.de/stecker-belegungen.html
  • Take CanAdaapterElm.X.production.unified.hex from hc04 folder of the latest binary package
  • Try to flash CanAdaapterElm.X.production.unified.hex. If it fails with the error "Cannot flash Device-ID", then edit it using Tools->Testmemory to the value in the original hex-file

Step3: Testing

  • Repower Elm327 adapter, connect to it over bluetooth and make a pair with it (standard PIN: 1234)
  • Connect to the bluetooth COM port assigned to the paired device on PC or use Serial Bluetooth Terminal for Android in HEX mode
  • When sending strings to the adapter you should at least get an echo from the adapter, otherwise there is a problem with the connections. Try to read ignition pin state with the following command (hex values):
    82 F1 F1 FE FE 60 The response should be: 82 F1 F1 FE FE 60 82 F1 F1 FE <state> <checksum> where bit 0 of <state> will be set to 1 if ignition is on.