OpenFNB58

Open-source tools for the FNIRSI FNB58 USB power meter / charger tester.

Author: Libor Tomsik, OK1CHP

Includes a Python CLI reader and a Qt 6 / QML desktop application with live charts, range measurement, protocol detection, fast-charge trigger, and CSV/Excel export. Works on Linux, Windows, and macOS over USB HID or Bluetooth LE.

---

Screenshots

Live streaming over BLE — 5 V / 1.73 A, USB SDP detected

BLE device picker — scans for nearby FNB58 devices

📐 Range measurement — drag to select, stats panel slides up

⚡ Fast-charge trigger popup — select protocol and target voltage

---

Downloads

Pre-built binaries are attached to each GitHub Release:

Platform	File	Notes
Linux	OpenFNB58-linux-x86_64.AppImage	chmod +x, then run
Windows	OpenFNB58-windows-x86_64.zip	Unzip and run fnb58app.exe
macOS	OpenFNB58-macos.dmg	Drag to Applications

---

Features

Python CLI (fnb58.py)

• Reads live measurements over USB HID (/dev/hidraw*) or Bluetooth LE
• Reports VBUS, IBUS, Power, D+, D−, Temperature, detected protocol
• Fast-charge trigger: --trigger PROTO_ID --voltage V (experimental)
• No root required — uses /dev/hidraw* (world-accessible) and unprivileged D-Bus BLE
• Modes: single shot, continuous, with configurable interval

Qt/QML GUI (app/)

• Live scrolling charts — Voltage/Current (dual axis) + Power (area fill)
• Live readout bar — VBUS, IBUS, Power, D+, D−, Temperature, Protocol badge
• Protocol detection — identifies USB SDP/DCP, QC 2.0/3.0, Apple, Samsung, Huawei FCP, USB PD from D+/D− voltages
• Fast-charge trigger — ⚡ Trigger button sends QC/FCP/SCP/PD trigger commands (experimental)
• USB and BLE transport — USB auto-connect; BLE scan popup picks from nearby devices
• Range measurement — click-drag on any chart to select a time window; shows energy (Wh/mWh/mAh), mean & peak V/I/P
• Energy marker — reset the Wh accumulator mid-session to measure a charging phase
• Zoom & pan — scroll wheel to zoom in/out, right-click drag to pan both charts
• Export — single ⬇ Export… button, native OS save dialog, CSV and Excel (.xlsx) output
• Dark Material theme, configurable time window, follow mode
• Cross-platform: Linux (AppImage), Windows (zip), macOS (dmg)

---

Hardware

Property	Value
Device	FNIRSI FNB58
USB VID:PID	2E3C:5558
USB interface	HID (interface #3) → /dev/hidraw*
BLE services	ffe0 (notify), ffe5 (write)
BLE notify char	ffe4 (in service ffe0)
BLE write char	ffe9 (in service ffe5)

---

Requirements

Python CLI

• Python 3.8+
• python3-dbus, python3-gi (for BLE mode; system packages)
• User must be in the plugdev group (for /dev/hidraw* access)

sudo usermod -aG plugdev $USER   # re-login after

Qt GUI

• Qt 6.5+ with: Core, Gui, Quick, QuickControls2, QML, Widgets, Bluetooth (optional)
• CMake 3.28+, C++20 compiler
• hidapi — libhidapi-dev (Linux), brew install hidapi (macOS), bundled via vcpkg (Windows)

Tested with Qt 6.9.2 from the Qt online installer.

For BLE on Linux, BlueZ must be running and the device pre-paired:

bluetoothctl
  scan on
  pair BA:03:18:7A:23:DF
  trust BA:03:18:7A:23:DF

---

Building from Source

cd app
cmake -B build -DCMAKE_BUILD_TYPE=Release .
cmake --build build --parallel
./build/bin/fnb58app

On Linux, Qt 6.9 from /opt/Qt is detected automatically if present.

---

USB HID Protocol

The FNB58 uses 64-byte HID reports over /dev/hidraw*.

Command	Bytes
INIT1	AA 81 00 … 8E
INIT2	AA 82 00 … 96
POLL	AA 83 00 … 9E

Response header: AA 04, followed by 4 × 15-byte samples.

Field	Offset	Type	Scale
Voltage	0	uint32-LE	÷ 100000
Current	4	uint32-LE	÷ 100000
D+	8	uint16-LE	÷ 1000
D−	10	uint16-LE	÷ 1000
Temp	12	uint16-LE	÷ 10

BLE Protocol

Stream frames on ffe4: AA [type] [data_len] [data…] [checksum]

Type	Data	Content
07	4 B	VBUS uint16-LE ÷ 1000, IBUS uint16-LE ÷ 1000
06	6 B	D+ uint16-LE ÷ 1000, D− uint16-LE ÷ 1000

Initialisation sequence sent to ffe9:

1. AA 81 00 F4 — wake
2. wait ~2 s
3. AA 82 00 A7 — start stream

---

Usage

Python CLI

# Single reading (USB)
python3 fnb58.py --once

# Continuous USB monitoring (1 s interval)
python3 fnb58.py --usb --interval 1

# BLE monitoring (auto-detect MAC)
python3 fnb58.py --ble

# BLE with explicit MAC
python3 fnb58.py --ble --mac BA:03:18:7A:23:DF

# Send QC 2.0 9V trigger, hold 3 s, then release (proto id 2 = QC 2.0 9V)
python3 fnb58.py --trigger 2 --voltage 9 --hold 3

Qt GUI

USB mode: select USB, leave Device/MAC blank, click ▶ Start.
BLE mode: select BLE, click ⊕ Scan, pick your device, click ▶ Start.

Measurement

Click and drag on any chart to select a time range.
A panel slides up showing energy, mean/peak voltage, current and power for the selection.
Double-click or press ✕ Clear to dismiss.

---

Project Structure

OpenFNB58/
├── fnb58.py                  Python CLI (USB HID + BLE)
└── app/
    ├── CMakeLists.txt
    ├── build.sh
    ├── main.cpp
    ├── DataRecord.h           Measurement sample struct
    ├── BaseTransport.h        Abstract QThread transport
    ├── UsbTransport.h/cpp     USB HID worker (hidapi, cross-platform)
    ├── BleTransport.h/cpp     BLE worker (Qt Bluetooth, cross-platform)
    ├── DeviceBackend.h/cpp    QML-exposed backend (energy, export, measure)
    ├── XlsxWriter.h/cpp       OOXML .xlsx writer (no external deps)
    ├── ZipWriter.h/cpp        STORE-only ZIP (used by XlsxWriter)
    └── qml/
        ├── Main.qml           Application window, toolbar, stats panel
        └── LiveChart.qml      Canvas-based scrolling dual-axis chart

---

Acknowledgements

• Protocol reverse-engineered with help from baryluk/fnirsi-usb-power-data-logger and Boondock-Echo/Article-Files.

License

GNU General Public License v3.0 — see LICENSE for full terms.

Copyright © 2024–2026 Libor Tomsik, OK1CHP