rpycrsf

Python library to control CRSF (Crossfire/ELRS) based drones from a Raspberry Pi.

rpycrsf opens the Pi's UART, packs stick/switch positions into CRSF RC_CHANNELS_PACKED frames, and streams them to the flight controller from a background thread at a steady rate — so the link doesn't drop into failsafe just because your script is busy doing something else.

Install

pip install rpycrsf

Or from a checkout:

pip install -e .

Raspberry Pi setup

1. Enable the hardware UART: sudo raspi-config → Interface Options → Serial Port → disable the login shell over serial, enable the hardware port.
2. On boards where Bluetooth uses the primary UART (Pi 3 / Pi 4 / Zero W), add dtoverlay=disable-bt to /boot/firmware/config.txt (or /boot/config.txt) and sudo systemctl disable hciuart so the PL011 UART is freed up for /dev/serial0 instead of being routed to Bluetooth via the slower mini-UART.
3. Add your user to the dialout group so you don't need sudo to open the port: sudo usermod -aG dialout $USER (log out/in to take effect).
4. Wire the CRSF TX module's UART RX/TX to the Pi's TX/GPIO14 and RX/GPIO15 pins (cross them: Pi TX → module RX, Pi RX → module TX), plus a common ground.
5. Use /dev/serial0 as the device — it's a symlink to the correct UART for your board.

Usage

import time
from rpycrsf import Drone

with Drone("/dev/serial0") as d:
    d.arm(True)
    d.set_mode(True)  # AUX2 -> angle mode
    d.set_sticks(throttle=0.5, roll=0.0, pitch=0.1, yaw=0.0)
    time.sleep(5)
# `close()` (called automatically by the `with` block) disarms and stops
# the sender thread before the port closes.

Drone starts a background thread on construction that resends the current channel state at update_rate_hz (150 Hz by default). Calling arm(), set_mode(), or set_sticks() only updates in-memory state — you don't need to call send() yourself in normal use; it exists for cases where you want a change reflected on the wire immediately instead of waiting for the next scheduled tick.

API

• Drone(device, baudrate=420000, update_rate_hz=150.0, auto_start=True)
• arm(armed: bool) — AUX1
• set_mode(angle: bool) — AUX2
• set_althold(enabled: bool) — AUX3 (Betaflight ALTHOLD mode range)
• set_sticks(roll=0.0, pitch=0.0, yaw=0.0, throttle=0.0) — roll/pitch/yaw are -1.0..1.0, throttle is 0.0..1.0
• send() — force an immediate transmit
• start() / stop() — control the background sender thread
• close() — disarm, stop the thread, close the port (called by __exit__)

See examples/basic_arm.py for a runnable example.

Lower level frame packing/CRC helpers and a raw CRSFPort (for sending custom frame types or reading telemetry) are available under rpycrsf.protocol if you need to go below the Drone API.

Development

pip install -e ".[dev]"
pytest