padctl

Terminal controller for KingSmith WalkingPad — BLE, cypherpunk green on black.

padctl is a single binary that finds your WalkingPad over Bluetooth, lets you start/pause/resume walks, watch live stats, and sync sessions to Google Fit — all from the terminal.

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Features

• Auto-connect by name — scans for your pad on startup, reconnects after BLE address rotation
• Full FTMS protocol — works with any treadmill advertising the Fitness Machine Service (UUID 0x1826)
• Session state machine — clean Start → Pause → Resume → End transitions, stats accumulate across pauses
• Live stats — speed, distance, steps, time, calories updated on every BLE notification
• Double-tap speed control — single tap ±0.1 km/h, double-tap within 300 ms jumps ±0.5 km/h
• Google Fit sync — browser-based OAuth on first use, refresh token persisted for subsequent syncs
• Persistent config — padctl.toml in your working directory, device address auto-updated on reconnect
• Debug logging — --debug flag writes structured logs to stderr, TUI stays on stdout

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Supported Devices

Verified on Kingfisher Z1 (KS-HD-Z1D).

Any treadmill that advertises the FTMS service (0x1826) with:

• Treadmill Data characteristic 0x2ACD (notify)
• Control Point characteristic 0x2AD9 (write + indicate)

should work. The Kingfisher Z1 also exposes proprietary KingSmith characteristics (0xfff1 / 0xfff2) for step count — padctl uses them when present.

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Install

Quickstart (no install required)

uvx padctl

Requires uv. Works on macOS and Linux out of the box.

pip

pip install padctl
padctl

Prerequisites for Linux

BlueZ and group membership are required for BLE access:

sudo apt install bluez
sudo usermod -aG bluetooth $USER
# log out and back in for the group to take effect

macOS — CoreBluetooth is available out of the box. No extra steps.

Build from source

Requires Rust 1.70+.

git clone https://github.com/jrosskopf/padctl
cd padctl
cargo build --release
./target/release/padctl

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Quick Start

1. Power on your WalkingPad
2. Run padctl — it scans and auto-connects by device name
3. Press s to start a session
4. ↑ / ↓ to adjust speed (double-tap for ±0.5 km/h jumps)
5. Press p to pause, r to resume, x to end the session

On first run with a new device: navigate the scan list with ↑/↓, press Enter to connect. The device address is saved to padctl.toml for automatic reconnection next time.

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Controls

Scanning

Key	Action
↑ / k	Cursor up
↓ / j	Cursor down
Enter	Connect to selected device
r	Rescan
c	Open config dialog
q	Quit

Session

Key	Action
s	Start (when idle)
p	Pause (when running)
r	Resume (when paused)
x	End session (when paused)
↑ / k	Speed +0.1 km/h
↓ / j	Speed −0.1 km/h
↑↑	Speed +0.5 km/h (double-tap within 300 ms)
↓↓	Speed −0.5 km/h (double-tap within 300 ms)
h	Jump to minimum speed (1.0 km/h)
l	Jump to maximum speed (6.0 km/h)
c	Config dialog
q	Quit

Session Summary

Key	Action
y	Upload session to Google Fit
n / x	Discard without uploading
q	Quit

Config Dialog

Key	Action
Tab / ↓	Next field
↑	Previous field
Enter	Activate focused field
Backspace	Delete character (text fields)
Esc	Close dialog

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CLI Flags

padctl [OPTIONS]

Options:
      --device-name <NAME>    Override saved device name
      --device-addr <ADDR>    Connect directly by MAC address (skips scan)
      --scan-timeout <SECS>   BLE scan timeout in seconds [default: 10]
      --debug                 Write debug log to stderr
  -h, --help                  Print help

Capture debug output while TUI runs:

padctl --debug 2>padctl-debug.log
tail -f padctl-debug.log   # in a second terminal

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Configuration

padctl.toml is created in your working directory on first connect.

device_addr   = "82:20:00:24:35:49"    # auto-updated after each connect
device_name   = "KS-HD-Z1D"            # name to scan for

# optional Google Fit OAuth credentials
fit_client_id     = ""
fit_client_secret = ""
fit_refresh_token = ""   # set automatically after first browser auth flow

The device address is re-saved every time padctl connects, so BLE address rotation (common on Kingfisher Z1 after power cycle) is handled transparently — reconnection falls back to name matching.

Override at runtime without editing the file:

padctl --device-name "WalkingPad"
padctl --device-addr AA:BB:CC:DD:EE:FF

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Google Fit

1. Go to Google Cloud Console → APIs & Services → Credentials
2. Create an OAuth 2.0 Client ID (type: Desktop app)
3. Add http://localhost as an authorized redirect URI (any port)
4. Copy the Client ID and Client Secret
5. Press c in padctl → enter Client ID → enter Client Secret → navigate to Save → Enter
6. After your next session, press y on the summary screen — a browser tab opens for consent
7. The refresh token is stored in padctl.toml; subsequent syncs happen without a browser prompt

Data uploaded per session: steps, distance (meters), calories (kcal), session start/end time, activity type = Treadmill.

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Troubleshooting

Scan finds nothing

• Make sure the WalkingPad is powered on and not connected to another device (phone app, remote)
• Try a longer scan: padctl --scan-timeout 20
• Verify BlueZ is running: systemctl status bluetooth

"Permission denied" on Linux

• Add yourself to the bluetooth group: sudo usermod -aG bluetooth $USER then re-login
• Or run once with sudo padctl to verify BLE access works, then fix the group

Address rotates after power cycle

• padctl saves the device name and re-matches by name — this is handled automatically
• If auto-match fails, press r to rescan; the new address is saved on connect

GATT setup fails or disconnects immediately

• Run with --debug and check padctl-debug.log for characteristic discovery errors
• Some devices require a delay before GATT operations after connect — the log will show where it fails

"RequestControl failed"

• Another client may hold FTMS control; disconnect the official app and retry

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Architecture

src/
├── main.rs          # tokio event loop, keyboard dispatch, BLE session task
├── types.rs         # BleEvent, Cmd, DiscoveredDevice
├── config.rs        # padctl.toml — serde + toml, device address persistence
├── error.rs         # AppError with thiserror
├── logger.rs        # stderr debug logging (--debug flag)
├── fit.rs           # Google Fit: OAuth 2.0 loopback + REST dataset upload
├── ble/
│   ├── protocol.rs  # FTMS + KingSmith proprietary packet codec, 66 unit tests
│   ├── scanner.rs   # btleplug scan, GATT discovery, notification stream
│   └── traits.rs    # WalkingPadBle async trait (enables mocking in tests)
├── session/
│   ├── mod.rs       # state machine: Idle → Running ↔ Paused → Idle
│   └── stats.rs     # cumulative stat accumulator, device counter reset handling
└── ui/
    ├── app.rs       # AppState, AppMode, double-tap timing, animation state
    └── render.rs    # ratatui: animated braille disc, stats panel, speed gauge, log

Key design decisions:

• All I/O on a single tokio runtime; BLE events and key events flow through mpsc channels
• Render is a pure read of AppState — no locks held during draw
• Stats use saturating_sub to survive device counter resets mid-session
• OAuth uses a TCP loopback listener on a random port — no external server needed

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Demo

The demo GIF was recorded with VHS. To regenerate it:

vhs padctl.tape

The tape file (padctl.tape) and the simulation script (demo/padctl-demo.sh) are both in the repository.

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License

MIT