pycasperglow 0.3.6

Async Python library for controlling Casper Glow lights via BLE

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():
    devices = await discover_glows(timeout=10.0)
    for device in devices:
        print(f"{device.name} ({device.address})")

asyncio.run(main())

Control a light

import asyncio
from pycasperglow import CasperGlow, discover_glows

async def main():
    devices = await discover_glows()
    if not devices:
        print("No Casper Glow found")
        return

    glow = CasperGlow(devices[0])
    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.

• turn_on() — Turn the light on.
• turn_off() — Turn the light off.
• name — Device name (property).
• address — Device BLE address (property).

discover_glows(timeout=10.0)

Scan for Casper Glow devices. Returns a list of BLEDevice objects. 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/ --strict
ruff check src/ tests/

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