openMC3000 — portable control & analysis for the SkyRC MC3000

Open-source, cross-platform control and analysis software for the SkyRC MC3000 — a 4-slot charger/analyzer that ships with Windows-only "PC Link" software. openMC3000 talks to the charger directly over USB-HID; nothing to install for the web app.

▶ Open the web app — desktop Chrome/Edge over WebHID. Plug the charger in (on its own DC supply), click Connect, pick the device.

It does something even SkyRC's own PC Link and GNU DataExplorer can't: start and stop a charge over USB, and configure a slot from scratch. DataExplorer declares the START/STOP opcodes but leaves them commented out — they work, and openMC3000 uses them.

Features

• Live telemetry — per-slot voltage, current, capacity, power, and temperature, polled once a second.
• Start / Stop the charger (global — the MC3000 has no per-slot start over USB).
• Full slot-program editing — battery type, mode, capacity, charge/discharge current, target & cut-off voltage, termination current. Every field verified to round-trip on hardware; the charger clamps to chemistry limits and the result is read back. Plus reset-to-defaults (chemistry-standard values).
• Live charts — per-slot voltage/current/capacity/temperature over a real time axis. The voltage chart auto-ranges from the slot's own targets and the cell chemistry, with green/amber/red safety bands and dashed target/cut-off reference lines.
• Charge/discharge modelling — a plain-word state (Bulk CC · Absorption CV · topping off · discharging · resting · done), device-measured internal resistance and energy, plus computed capacity-vs-rated, C-rate, ΔT, peak/avg, and a rough time-remaining estimate. Internal resistance is the primary battery-health indicator.
• Session recording → CSV export — capture a full charge/discharge curve and download it (wide format: time_iso, elapsed_s, then status/V/mA/mAh/°C per slot) for spreadsheets.

Every protocol claim behind these is marked verified/unverified in PROTOCOL.md; the charger used for verification runs firmware 1.25 / hardware 2.2.

Two front-ends, one codec

The wire protocol (src/protocol) and a transport interface (src/transport) are shared; each front-end is a thin consumer:

• web/ — the WebHID app above (TypeScript + Vite, no framework). Deploys to GitHub Pages on every push.

• src/cli.ts — a zero-dependency Node CLI over /dev/hidraw:

  $ npm run cli system
  serial 100083  firmware 1.25  hardware 2.2
  
  $ npm run cli status
  slot 1: charge    LiIon    3.735V  1005mA 13mAh
  slot 2: standby   LiIon    (empty)
  
  $ npm run cli start      # …and: watch, stop

Running it

Web app: just open https://glassontin.github.io/openmc3000/ in desktop Chrome or Edge (WebHID is Chromium-desktop only). To hack on it: cd web && npm install && npm run dev.

CLI: Node 22+ (for --experimental-strip-types), no dependencies. On Linux, /dev/hidraw* is root-only by default, so add a udev rule:

KERNEL=="hidraw*", ATTRS{idVendor}=="0000", ATTRS{idProduct}=="0001", MODE="0660", GROUP="plugdev"

Drop that in /etc/udev/rules.d/99-skyrc-mc3000.rules, udevadm control --reload, replug. Note it targets hidraw, not SUBSYSTEM=="usb" — we speak HID reports, not libusb.

The charger must be powered from its own DC supply; USB does not power it. Its vendor id is literally 0x0000, which some hubs refuse to enumerate — use a motherboard port if it doesn't appear.

Repo layout

• PROTOCOL.md — the wire protocol, with provenance and per-field verification.
• src/protocol/ — framing, command codec, and decoders (transport-agnostic, shared).
• src/transport/ — the byte-level seam: hidraw.ts (Node) and webhid.ts (browser).
• src/cli.ts — status, system, watch, start, stop.
• web/ — the WebHID app (npm run dev / build); Pages workflow in .github/workflows.
• bridge/ — MQTT / Home Assistant bridge (headless telemetry publisher).
• test/ — npm test (node's built-in runner, no framework).

Safety

This writes charge parameters to a device that charges lithium cells, and the charger does not range-check what it is sent. Probed on hardware, the MC3000 accepted a 1.0 V and a 2.0 V charge end-voltage on a NiMH without complaint. There is no firmware backstop behind the values in the editor: review every field before saving, and know your cell.

start begins a real charge or discharge at whatever the slot is programmed for. openMC3000 has no protections beyond the charger's own, and cannot know that a program suits the cell you inserted.

Reset to defaults fills chemistry-standard figures and derives the currents from the capacity you enter at 0.5C — they are a starting point for review, not a recommendation for your cell. They are pinned by tests (test/defaults.test.ts), because in practice this is where the mistakes have been: an early NiMH ceiling of 1.50 V terminated a charge at 9% of the cell's rating, and a flat 1000 mA default would have been 2.9C into a 10440.

What has actually been exercised

Firmware / hardware	1.25 / 2.2, a single unit
Chemistries run on real cells	LiIon (21700, 18650) and NiMH (AA)
Chemistries not yet run	LiFe, LiIo4.35, NiCd, Eneloop, NiZn, RAM — their defaults are chemistry-standard figures that no cell here has been charged against
Browsers	Chrome / Edge only. WebHID is not implemented in Firefox or Safari and the web app cannot work there — use the CLI or the bridge instead.

Reports from other firmware revisions, chemistries and cells are welcome — that is the gap.

Legal

Independent interoperability implementation, from two sources — neither of them SkyRC's proprietary software:

• GNU DataExplorer (GPL-3.0-or-later): its MC3000 plugin was read openly for the wire framing, command codes and field offsets. This is an openly-credited GPL derivative — not clean-room — and GPLv3 §13 permits combining it into this AGPL-3.0 work. Facts are cited by file and line in PROTOCOL.md; no code was copied.
• Direct observation of the device: values confirmed by writing a known setting over USB-HID and reading it back.

No SkyRC binary or firmware was decompiled, disassembled, or copied, and no SkyRC code, resources, or firmware are included or derived from. The documented items — command codes, register offsets, wire framing — come from DataExplorer and from observing the device's own USB-HID interface; they are interface facts, not copyrightable expression.

"SkyRC" and "MC3000" are trademarks of SkyRC Technology Co., Ltd. This project is independent and not affiliated with or endorsed by them.

Licensed under GNU AGPL-3.0-or-later (see LICENSE).

Copyright (C) 2026 Ian Williams