ArduinoOBI

This is the original implementation of a Makita diagnostic dongle (called ArduinoOBI) that connects a Makita LTX battery to a PC. It uses the original Open Battery Information resources and runs on Arduino UNO/Arduino Nano.

This YouTube video explains how to build the adapter and provides free 3D printing files for a matching enclosure.

Overview

The original ArduinoOBI was the first adapter capable of querying Makita LTX batteries and also unlocking batteries that the BMS has locked.

It is based on the extensive reverse‑engineering work by Martin Jansson and uses an Arduino Nano to bridge the Makita LTX 1‑Wire interface to a PC over USB.

PC Software

The Arduino only performs signal translation; all higher‑level processing is handled by the Python‑based PC application OpenBatteryInformation.exe.

The PC software provides a convenient way to manage Makita LTX batteries. However, offloading the processing to a PC application introduces several limitations:

• Not portable – Requires a PC/laptop connection.
• OS compatibility – Limited to supported operating systems.
• Security – False malware warnings when downloading/running the executable.

Because the executable is simply a wrapper around a Python script, you can alternatively download and run the Python script directly. Once running, it offers a very convenient way to inspect Makita LTX batteries in a lab environment.

The Arduino Nano’s limited memory and performance made a separate PC software necessary. Derived projects ported the firmware to much more powerful ESP32 microcontrollers, delivering truly portable solutions with integrated front end.

Building Adapter

To build the adapter that connects to your PC, only a handful of low‑cost parts are required:

• Arduino Nano clone:
  A low‑cost Arduino Nano‑compatible board (around €1.50) works fine, yet you can also use an original Arduino UNO or Nano of course.

  

• Connector cable:
  Use a Makita charger replacement connector cable to interface cleanly with the battery.

  

• Other items:
  You need two 4.7 kΩ resistors and a spade connector, keeping the total hardware cost to under €5.

Step‑By‑Step Instructions

Rather than repeating the complete build process here, follow the original instructions and/or watch this YouTube video.

Wiring Makita Connector

While the source instructions are mostly great, they do not clearly illustrate the orientation and wiring of the yellow connector. To clarify, here is the pin assignment:

The two active pins connect to Arduino Nano GPIOs D6 and D8:

GPIO	Connect to
D6	1-Wire
D8	Enable

Pull‑Up Resistors

Both D6 and D8 must be pulled up to 5V using 4.7 kΩ resistors to meet the 1‑Wire electrical requirements. When soldering, ensure the resistor leads cannot short to nearby components or tracks on the Arduino board.

Ground Connection

The Arduino GND pin needs to be connected to the Makita battery - terminal to share a common reference for the 1‑Wire interface. A crimped spade connector, as demonstrated in the YouTube build video, is a practical way to attach to the battery terminal.

Using ArduinoOBI

Using ArduinoOBI is straightforward: connect the Arduino to your PC via USB, then slide ArduinoOBI onto your Makita LTX battery.

On your PC, start OpenBatteryInformation.exe.

Windows Defender may classify this download as malware (even though the project is open source and community‑audited). In that case, some guides suggest temporarily disabling Windows Security Realtime Protection to run the executable, but using the pure Python version is safer from a security perspective.

In the application window:

1. In the two drop‑down boxes at the top left, select Makita LXT and Arduino OBI.
2. In the Select Port list, choose the COM port assigned to your Arduino.
3. Click Connect.
4. In the top‑center section, click Read battery model and Read battery data to populate all details in the list below.

Unlocking Battery

Occasionally, the internal BMS will lock a battery, making it unusable.

While lockouts often indicate legitimate issues such as cell defects, overload events, or other safety‑critical faults, there are also many reports of otherwise healthy batteries being locked purely by software. In such cases, you can click Clear Errors in the software to attempt to unlock the battery.

Proceed entirely at your own risk: overriding a safety lock on a damaged battery can lead to overheating or fire.

Compiling Firmware

The reference documentation uses the Arduino IDE to compile and upload the firmware to an Arduino Nano or UNO.

If you prefer PlatformIO, you can either download the ready‑to‑build PlatformIO ArduinoOBI project or follow the manual steps below.

The steps below assume you are already familiar with PlatformIO and VS Code.

Manually Creating PlatformIO Project

In PlatformIO, create a new project and select your target microcontroller. Once the project is created, adjust it in the file explorer:

1. Open platform.ini and review the auto‑generated settings. For an Arduino Nano Clone, use:

    [env:nano_old]
    platform  = atmelavr
    board     = nanoatmega328
    framework = arduino
    upload_speed = 57600
   

2. In your browser, open Arduino OBI/main.cpp and copy the complete source code.
3. In VS Code, open src\main.cpp and replace its contents with the copied source.
4. In the VS Code Explorer, right‑click lib → New Folder and name it OneWire2.
5. In your browser, navigate to ArduinoOBI/lib/OneWire where you find OneWire2.cpp and OneWire2.h.
6. Open OneWire2.cpp, copy the source, then in VS Code create OneWire2.cpp inside the OneWire2 folder (exact file name and casing) and paste the code. Save the file.
7. Repeat the previous step for OneWire2.h.
8. In the Explorer, right‑click the OneWire2 folder → New Folder and name it util.
9. In your browser, navigate to ArduinoOBI/lib/OneWire/util, which contains OneWire_direct_gpio.h and OneWire_direct_regtype.h.
10. Copy OneWire_direct_gpio.h, then in VS Code create a file with the same name under OneWire2/util, paste the contents, and save.
11. Repeat for OneWire_direct_regtype.h.

Now everything is in place; in PlatformIO, choose Upload to build and flash the firmware onto your microcontroller.

Materials

• ArduinoOBI (platformio):
  Complete sample project, ready to be built in platformio: download and unpack this zip, then in VSCode choose File / Open Folder.

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