DM40GUI

A Windows desktop app for DM40-series multimeters and EL15 electronic loads over Bluetooth Low Energy. Tkinter front-end, a custom WinRT BLE transport, and zero third-party Python dependencies at runtime.

Tip

Prebuilt binaries are available on the Releases page.

Warning

Windows only. The transport layer talks to WinRT BLE GATT directly; there is no maintained Linux or macOS port.

Contents

• Features
• Device Support
• Requirements
• Run from Source
• Build for Release
• Keybinds
• Architecture
• Protocol Notes
• Notes
• License

Features

• One binary, two device families: handlers are dispatched dynamically after the device is identified.
• Scrolling waveform with live value, pause/resume, click-to-pin, drag-to-select range with min / max / Δ.
• Raw packet inspector with inline CRC pass/fail tags and integrated find popup.
• One-shot CSV buffer export or continuous CSV recording.
• 17 built-in themes with a live preview browser; selection is persisted across sessions.
• Release build is tuned for small size: Nuitka one-file + size-oriented MSVC flags + aggressive stdlib pruning.

Device Support

Device	Status	UI / Telemetry	Controls
DM40 series	Supported	Live reading, waveform, raw packet view, stats	Hold, auto, relative, range and mode switching
EL15	Experimental	Voltage / current / power, waveform, raw packet view, stats	Load on/off, CC / CV / CR / CP / CAP / DCR mode switching, setpoint entry

DM40

• Large primary reading with auxiliary values.
• Mode, range, battery, charging, lock, and hold state rendering.
• Hold, auto-range, relative, capacitance, diode / continuity, frequency, and temperature controls.
• Roughly matches atk-xtool feature coverage for day-to-day meter use.

EL15

• Dedicated voltage, current, and power readout cells.
• Runtime, temperature, fan speed, mode, load state, and setpoint display.
• CC, CV, CR, CP, CAP (battery capacity), and DCR (DC resistance) mode switching from the main control bar.
• CAP mode shows accumulated energy (Wh) and capacity (Ah) in place of the setpoint.
• DCR mode shows the I1 / I2 test currents and the measured milliohm resistance.
• Device-only modes (POW [A], POW [DT], ADV [L], ADV [S]) surface as a single disabled radio that tracks the active mode; the setpoint entry is disabled in these modes.
• Load control and editable setpoint command entry.

Requirements

• Windows 10 version 1703 (Creators Update, build 15063) or newer. The BLE GATT APIs this app relies on (IBluetoothLEDevice3, IGattDeviceService3) were introduced in that release; IBluetoothLEDevice6 connection tuning is used when available and skipped otherwise.
• Python 3.13+ with Tkinter (source runtime only).
• MSVC Build Tools compatible with Nuitka --msvc=latest (release build only).

Note

Other Python versions may work, but are currently untested.

Run from Source

py -3.13 main.py

No extra package install is required for source execution.

Build for Release

Install the build dependency:

py -3.13 -m pip install --upgrade nuitka

Then run:

build_release.cmd

The release path is intentionally size-focused:

• one-file Nuitka build
• size-oriented compiler and linker flags
• precompiled minimal ctypes shim for frozen builds
• aggressive exclusion of unused stdlib modules and Tcl/Tk payloads
• optional module-closure reports for auditing import growth

The build script is CI-friendly:

• deterministic compiler and linker environment setup
• non-zero exit on failure
• configurable via DM40_* environment variables

Build environment variables:

Variable	Purpose
DM40_PYTHON	Python launcher or command (default: py -3.13)
DM40_OUT_DIR	Build output directory
DM40_CCFLAGS	Additional compiler flags
DM40_LINKFLAGS	Additional linker flags
DM40_NUITKA_FLAGS	Additional Nuitka flags
DM40_MODE_FLAGS	Build mode flags (default: --deployment)
DM40_CONSOLE_MODE	Nuitka console mode (disable, attach, force)
DM40_MSVC	Nuitka MSVC selector (default: latest)
DM40_JOBS	Parallel compile jobs
DM40_EMIT_MODULE_REPORTS	Emit modules.txt and XML report (1 local default, 0 when CI is set)

Minimal CI example:

set DM40_PYTHON=py -3.13
set DM40_OUT_DIR=build\ci\nuitka
call build_release.cmd

Keybinds

Scope	Keybind	Action
Global	P	Pause or resume waveform updates
Global	R	Start or stop waveform CSV recording
Global	Ctrl+S	Save the current waveform buffer to CSV
Global	Ctrl+C	Copy the current reading text
Raw packet view	Ctrl+F	Open the find popup
Raw packet view	Enter / F3	Next match
Raw packet view	Shift+Enter / Shift+F3	Previous match
Raw packet view	Esc	Close the find popup or clear its focus
Waveform	Left click on trace	Pin a tooltip at a sample
Waveform	Left-click drag	Select a range and show min / max / Δ
Waveform	Right click	Clear the pinned point or current selection

Architecture

Path	Description
main.py	Entry point; installs frozen-build shims before launching the app
shared/base_app.py	Single-window Tk app, scan/connect flow, waveform view, and handler selection
shared/ble_worker.py	Shared BLE worker plus device-family probe
shared/device_registry.py	Single-source registry of supported device handlers
shared/nanowinbt/	Custom Windows BLE and WinRT transport layer
shared/mini_asyncio.py	Small async runtime used instead of full asyncio
dm40/app.py	DM40 handler, controls, and UI updates
dm40/parsing.py	DM40 packet parsing and meter-state decoding
dm40/protocol_constants.py	DM40 commands, flags, scale maps, and mode groups
el15/app.py	EL15 handler, controls, and UI updates
el15/protocol_constants.py	EL15 commands and status packet parsing
GUI/	Shared widgets, controls, theming, and custom dialogs
build_release.cmd	One-file Nuitka build script

Protocol Notes

Reverse-engineered from BLE HCI captures and device traffic inspection.

Shared BLE Endpoints

Both device families currently use the same BLE service and characteristic layout in the shared worker:

Direction	UUID
Service	0000fff0-0000-1000-8000-00805f9b34fb
Notify	0000fff1-0000-1000-8000-00805f9b34fb
Write	0000fff3-0000-1000-8000-00805f9b34fb

DM40 Protocol

DM40 command frames are 6 bytes:

AF 05 03 <cmd> <arg> <checksum>

Checksum formula:

(-sum(first_5_bytes)) & 0xFF

Common commands:

CMD_ID          af 05 03 08 00 41
CMD_READ        af 05 03 09 00 40
CMD_HOLD_ON     af 05 03 04 01 01
CMD_HOLD_OFF    af 05 03 04 01 00
CMD_AUTO_ON     af 05 03 03 01 01
CMD_AUTO_OFF    af 05 03 03 01 00
CMD_RELATIVE    af 05 03 05 01 01
CMD_CAP         af 05 03 06 01 03
CMD_DIODE       af 05 03 06 01 04
CMD_CONT        af 05 03 06 01 44
CMD_HZ          af 05 03 06 01 05
CMD_TEMP        af 05 03 06 01 45

DM40 notifications use two main packet families:

• Model ID: prefix DF 05 03 08 14
• Measurement: prefix DF 05 03 09

DM40 measurement decode summary:

Byte(s)	Field
data[5]	Mode and range flag (FLAG_INFO)
data[6]	Status byte
data[14:16]	Primary counts (m1, little-endian)
data[12:14]	Secondary counts (m2, little-endian)
data[10:12]	Tertiary counts (m3, little-endian)
data[-8]	Scale and sign slot 1
data[-9]	Scale and sign slot 2
data[-10]	Scale and sign slot 3

CRC check:

(sum(all_bytes) & 0xFF) == 0

DM40 status byte (data[6]) summary:

Bits	Meaning
& 0x07	Battery level (0-5 bars)
& 0x08	Charging
& 0x40	Screen lock
& 0x80	Hold

EL15 Protocol

EL15 status notifications use header:

DF 07 03 08

EL15 poll command:

AF 07 03 08 00 3F

Common EL15 commands:

CMD_LOAD_ON     af 07 03 09 01 04
CMD_LOAD_OFF    af 07 03 09 01 00

Mode switch commands share a common prefix AF 07 03 03 01 <mode>:

Mode	ID	Command
CC	0x01	af 07 03 03 01 01
CAP	0x02	af 07 03 03 01 02
CV	0x09	af 07 03 03 01 09
DCR	0x0A	af 07 03 03 01 0a
CR	0x11	af 07 03 03 01 11
CP	0x19	af 07 03 03 01 19

Device-only modes observed in status packets, cannot be set from the app

Mode	ID	Label
Power dynamic test	0x03	POW [DT]
Advanced list	0x04	ADV [L]
Power (auto)	0x0B	POW [A]
Advanced scan	0x0C	ADV [S]

Setpoint command layout:

AF 07 03 04 04 <float32 payload>

The EL15 parser treats valid status packets as 28-byte frames. The fixed fields are:

Byte(s)	Field
data[5] & 0x1F	Mode ID (ready bit folded in for CC/CV/CR/CP)
data[5] & 0x01	Ready / measuring flag (clear while in device menus)
(data[5] >> 6) | ((data[6] & 0x01) << 2)	Fan speed (0-5)
data[6] & 0x02	Load on
data[6] & 0x04	Panel lock
data[7:11]	Voltage (float32)
data[11:15]	Current (float32, unused in DCR/ADV/POW)

Bytes [15:19], [19:23], [23:27] are mode-specific:

Mode	[15:19]	[19:23]	[23:27]
CC / CV / CR / CP	Runtime (int32, s)	Temperature (float32, °C)	Setpoint (float32)
CAP	Runtime (int32, s)	Energy (float32, mWh)	Capacity (float32, mAh)
DCR	I1 (float32, A)	I2 (float32, A)	Resistance (float32, mΩ)
ADV [L] / ADV [S] / POW [A] / POW [DT]	unused	unused	unused

Derived values shown in the UI:

• Power is computed as voltage * current
• CAP / DCR reuse the setpoint info row to show energy/capacity or I1/I2/R respectively
• Mode label is resolved from the mode byte via MODE_NAMES
• Setpoint unit and precision depend on the active EL15 mode

Notes

Warning

This project is still in an early reverse-engineering stage. DM40 scale and range coverage is incomplete, and unknown packet variants can still surface as missing flag support.

Note

If the app crashes with a DM40 KeyError during parsing, that usually means a scale or range flag has not been mapped yet. Please report it with the raw packet if possible.

Note

This project is not affiliated with, endorsed by, or associated with Alientek or any of its subsidiaries.

License

Licensed under LICENSE.