pycasperglow

Async Python library for controlling Casper Glow lights via BLE.

Built on bleak and designed for use as a backend for Home Assistant integrations.

Installation

pip install pycasperglow

Usage

Discover devices

import asyncio
from pycasperglow import discover_glows

async def main():
    async for device in discover_glows(timeout=10.0):
        print(f"{device.name} ({device.address})")

asyncio.run(main())

Control a light

import asyncio
from pycasperglow import CasperGlow, discover_glows

async def main():
    glow = None
    async for device in discover_glows():
        glow = CasperGlow(device)
        break
    if glow is None:
        print("No Casper Glow found")
        return
    await glow.turn_on()
    await asyncio.sleep(5)
    await glow.turn_off()

asyncio.run(main())

Home Assistant integration

When used within Home Assistant's Bluetooth stack, pass the managed BleakClient to avoid connection conflicts:

glow = CasperGlow(ble_device, client=bleak_client)
await glow.turn_on()

When an external client is provided, pycasperglow will not disconnect it — the caller retains ownership.

API

CasperGlow(ble_device, client=None)

Async client for a single Casper Glow light.

Method / Property	Description
turn_on()	Turn the light on
turn_off()	Turn the light off
pause()	Pause the active dimming sequence
resume()	Resume a paused dimming sequence
set_brightness_and_dimming_time(level, dimming_time_minutes)	Set brightness (60–100 %) and dimming duration (15, 30, 45, 60, or 90 min). Both required.
query_state()	Query current device state; returns GlowState
handshake()	Test connectivity without sending a command
register_callback(cb)	Register a callback invoked on every state update
state	Current GlowState property (last known, or default)
name	Device name (property)
address	BLE address (property)

GlowState

Dataclass returned by query_state() and passed to registered callbacks.

Field	Type	Description
is_on	bool | None	True when on, False when off
is_paused	bool | None	True when dimming is paused
is_charging	bool | None	True when plugged in to charger
battery_level	BatteryLevel | None	Discrete battery level
brightness_level	int | None	Last-set brightness % (not reported by device)
dimming_time_minutes	int | None	Remaining dimming time (from device)
configured_dimming_time_minutes	int | None	Total configured duration

BatteryLevel

IntEnum with four members: PCT_25, PCT_50, PCT_75, PCT_100. Each has a .percentage property returning 25, 50, 75, or 100.

discover_glows(timeout=10.0)

Scan for Casper Glow devices. Async generator that yields BLEDevice objects as they are found. For standalone use — Home Assistant uses its own discovery.

is_casper_glow(device, adv)

Returns True if a BLEDevice and AdvertisementData match a Casper Glow (by service UUID or name prefix).

Exceptions

Exception	Description
CasperGlowError	Base exception
ConnectionError	Connection or handshake failure
HandshakeTimeoutError	Device did not become ready in time
CommandError	Failed to send a command

Examples

See the examples/ directory for runnable scripts. To discover nearby Casper Glow lights and turn them on:

python examples/discover_and_turn_on.py

Development

python3 -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

Run checks:

pytest tests/ -v --cov=pycasperglow
mypy src/ tests/ examples/ --strict
ruff check src/ tests/ examples/

Protocol

The BLE protocol was partially reverse-engineered from dengjeffrey/casper-glow-pro. The connection flow is:

1. Connect and subscribe to notifications on the read characteristic
2. Write the reconnect packet
3. Wait for a notification containing the ready marker
4. Extract the session token from the notification
5. Build and write the action packet (header + token + action body)
6. Disconnect

License

MIT