JoyCam

JoyCam — bridge your joystick, receiver, or transmitter to the CRSF (Crossfire), IBUS (FlySky) and SBUS (Futaba) protocols on Linux.
Receive RC channels and link telemetry from an ELRS / TBS Crossfire receiver, generate IBUS or SBUS control packets, or read a USB joystick and map its axes to channel values — all in one toolbox.

Optimised for embedded Linux and OpenIPC-compatible devices (IP cameras, NVRs based on Sigmastar, Goke, Hisilicon SoCs). Run crsf_rx, ibus_rx or sbus_rx directly on the camera's UART — no separate computer needed.

Tools

Tool	Description	OpenIPC
`crsf_rx`	Reads CRSF frames from a serial port or RFC 2217 endpoint, parses 16 RC channels (11-bit) and link statistics (RSSI, LQ, RF power).	✅
`crsf_tx`	Generates CRSF RC channel packets at 100 Hz with a sawtooth sweep. Supports RFC 2217 (`tcp:host:port`).	✅
`ibus_rx`	Reads IBUS (FlySky) frames from a serial port or RFC 2217 endpoint, parses 14 RC channels.	✅
`ibus_tx`	Generates IBUS RC channel packets at 50 Hz with a sawtooth sweep. Supports RFC 2217 (`tcp:host:port`).	✅
`sbus_rx`	Reads SBUS (Futaba) frames from a serial port or RFC 2217 endpoint, parses 16 RC channels. USB-UART needs hardware inverter.	✅
`sbus_tx`	Generates SBUS RC channel packets at 100 Hz with a sawtooth sweep. Supports RFC 2217 (`tcp:host:port`). USB-UART needs hardware inverter.	✅
`joystick`	Reads a USB joystick/gamepad via evdev and maps axes/buttons to RC channels over CRSF, SBUS, or IBUS. Output to UART, RFC 2217, or screen.	⚠️ needs USB host

Requirements

Linux (tested on Ubuntu 22.04 / Debian 12, OpenIPC firmware)
gcc with GNU99 support (or cross-compiler for target SoC)
No external libraries. Pure POSIX + Linux ioctl (with POSIX sockets for RFC 2217). Only depends on the C standard library and kernel headers (linux/input.h for evdev support).

Cross-compilation for OpenIPC (arm-linux-gnueabihf / aarch64-linux-gnu)

CROSS=arm-linux-gnueabihf- make

Build

make

Seven binaries are produced: crsf_rx, crsf_tx, ibus_rx, ibus_tx, sbus_rx, sbus_tx, joystick.

Usage

Receive CRSF data

# Local serial port
./crsf_rx /dev/ttyUSB0 [-d]

# Remote via RFC 2217
./crsf_rx tcp:192.168.1.5:2217 [-d]

Output:

Listening for CRSF data on /dev/ttyUSB0...
Channels: 0:992 1:1020 2:988 3:1700 4:992 5:992 6:992 7:992 8:992 9:992 10:992 11:992 12:992 13:992 14:992 15:992
Link Quality: 99%  RSSI1: -45 RSSI2: -48 Power: 100

Use -d to hex dump every raw CRSF frame alongside the decoded channels.

On OpenIPC cameras the ELRS receiver is typically connected to the camera's UART1 or UART2 (e.g. /dev/ttyAMA1).

Receive IBUS data

# Local serial port
./ibus_rx /dev/ttyUSB0 [-d]

# Remote via RFC 2217
./ibus_rx tcp:192.168.1.5:2217 [-d]

Output:

Listening for IBUS data on /dev/ttyUSB0...
Channels: 0:1500 1:1500 2:1500 3:1500 4:1500 5:1500 6:1500 7:1500  | 8:1500 9:1500 10:1500 11:1500 12:1500 13:1500

IBUS uses 115200 baud, 14 channels in the 1000–2000 range.

Receive SBUS data

# Local serial port
./sbus_rx /dev/ttyAMA0 [-d]

# Remote via RFC 2217
./sbus_rx tcp:192.168.1.5:2217 [-d]

SBUS uses 100000 baud 8E2 with an inverted signal. On most SoC UARTs the inversion is handled in hardware; USB-UART adapters typically need an external inverter circuit.

Output:

Listening for SBUS data on /dev/ttyAMA0...
Channels: 0:992 1:992 2:992 3:992 4:992 5:992 6:992 7:992 8:992 9:992 10:992 11:992 12:992 13:992 14:992 15:992

Transmit test frames

CRSF (100 Hz):

# Local serial port
./crsf_tx /dev/ttyACM0 [-a <ch>]

# Remote via RFC 2217
./crsf_tx tcp:192.168.1.5:2217 [-a <ch>]

IBUS (50 Hz):

./ibus_tx /dev/ttyACM0 [-a <ch>]
./ibus_tx tcp:192.168.1.5:2217 [-a <ch>]

SBUS (100 Hz):

./sbus_tx /dev/ttyAMA0 [-a <ch>]
./sbus_tx tcp:192.168.1.5:2217 [-a <ch>]

Channel 0 sweeps by default. Use -a <ch> to sweep a different channel.

Read joystick / full-chain bridge

joystick reads a USB joystick via evdev and maps its axes/buttons to channel values. It supports CRSF (-p crsf), IBUS (-p ibus), and SBUS (-p sbus). Five display modes are available:

Mode	Command	Behaviour
Status line	`./joystick -p crsf\|ibus\|sbus <evdev>`	Show all channels every frame
Verbose	`./joystick -p crsf\|ibus\|sbus <evdev> -v`	Print every axis/button event + HEX dump
Transmit	`./joystick -p crsf\|ibus\|sbus <evdev> <port>`	Send frames silently
Tx + status	`./joystick -p crsf\|ibus\|sbus <evdev> <port> -d`	Send + status line
Tx + verbose	`./joystick -p crsf\|ibus\|sbus <evdev> <port> -v`	Send + raw events

<port> can be a local serial device (/dev/ttyS0) or an RFC 2217 TCP endpoint (tcp:host:port).

Find your evdev device with:

ls -l /dev/input/by-id/*-joystick

Examples:

# Debug — see axis/button events (CRSF)
./joystick -p crsf /dev/input/by-id/usb-045e_028e-event-joystick

# Silent transmit — IBUS over local UART
./joystick -p ibus /dev/input/by-id/usb-045e_028e-event-joystick /dev/ttyS0

# Silent transmit — SBUS over RFC 2217
./joystick -p sbus /dev/input/by-id/usb-045e_028e-event-joystick tcp:192.168.1.5:2217

# Debug + transmit over RFC 2217 (CRSF)
./joystick -p crsf /dev/input/by-id/usb-045e_028e-event-joystick tcp:192.168.1.5:2217 -d

Testing / Verification

Virtual serial port (no hardware required)

Create a virtual serial pair with socat:

socat -d -d pty,raw,echo=0,link=/tmp/ttyV0 \
            pty,raw,echo=0,link=/tmp/ttyV1

In terminal A — transmit test frames:

# CRSF (100 Hz)
./crsf_tx /tmp/ttyV0

# or IBUS (50 Hz)
./ibus_tx /tmp/ttyV0

# or SBUS (100 Hz) — uses custom 100000 baud via termios2
./sbus_tx /tmp/ttyV0

In terminal B — receive and decode:

# CRSF
./crsf_rx /tmp/ttyV1

# or IBUS
./ibus_rx /tmp/ttyV1

# or SBUS
./sbus_rx /tmp/ttyV1

Full chain: joystick → receiver (loopback)

Example loopback test using a virtual serial pair:

Create a virtual serial pair:

socat -d -d pty,raw,echo=0,link=/tmp/ttyV0 \
            pty,raw,echo=0,link=/tmp/ttyV1

In terminal A — run the joystick bridge:

# CRSF
./joystick -p crsf /dev/input/by-id/usb-045e_028e-event-joystick /tmp/ttyV0 -d

# or IBUS
./joystick -p ibus /dev/input/by-id/usb-045e_028e-event-joystick /tmp/ttyV0 -d

# or SBUS
./joystick -p sbus /dev/input/by-id/usb-045e_028e-event-joystick /tmp/ttyV0 -d

In terminal B — receive frames:

# CRSF
./crsf_rx /tmp/ttyV1

# or IBUS
./ibus_rx /tmp/ttyV1

# or SBUS
./sbus_rx /tmp/ttyV1

Move joystick sticks — the receiver shows live channel values.

RFCP 2217 loopback (remote serial bridge)

Bridge a local serial port to TCP, then connect from another machine:

# On the machine with the serial device
socat TCP-LISTEN:2217,reuseaddr,fork FILE:/dev/ttyS0,raw,nonblock,waitlock=/tmp/s0.lock

# On the remote machine
./crsf_rx tcp:192.168.1.5:2217
./crsf_tx tcp:192.168.1.5:2217
./joystick -p crsf /dev/input/event0 tcp:192.168.1.5:2217 -d

Axis mapping (all protocols)

evdev code	Meaning	CRSF channel	IBUS channel	SBUS channel
0	Left stick X (LX)	ch0	ch0	ch0
1	Left stick Y (LY)	ch1	ch1	ch1
2	Right stick X (RX)	ch2	ch2	ch2
5	Right stick Y (RY)	ch3	ch3	ch3
9	Left trigger (LT)	ch4	ch4	ch4
10	D-pad X axis	ch5	ch5	ch5
16	D-pad Y axis	ch6	ch6	ch6
17	Extra axis	ch7	ch7	ch7

Button mapping (all protocols)

evdev code	Linux name	CRSF channel	IBUS channel	SBUS channel
304	`BTN_SOUTH` (A / cross)	ch8	ch8	ch8
305	`BTN_EAST` (B / circle)	ch9	ch9	ch9
306	`BTN_NORTH` (X / triangle)	ch10	ch10	ch10
307	`BTN_WEST` (Y / square)	ch11	ch11	ch11
308	`BTN_TL` (left bumper)	ch12	ch12	ch12
309	`BTN_TR` (right bumper)	ch13	ch13	ch13
310	`BTN_TL2` (left trigger)	ch14	ch14	ch14
311	`BTN_TR2` (right trigger)	ch15	ch15	ch15
312	`BTN_SELECT` (back)	ch16	ch16	ch16
313	`BTN_START` (start)	ch17	ch17	ch17
314	`BTN_THUMBL` (left stick click)	ch18	ch18	ch18
315	`BTN_THUMBR` (right stick click)	ch19	ch19	ch19

All other buttons are ignored.

RFC 2217 (Serial-over-TCP) support

All tools can connect to a remote serial port via RFC 2217 (Telnet COM Port Control Option) — just use a tcp:host:port URI instead of a device path:

# Connect to an RFC 2217 server instead of a local UART
./crsf_rx tcp:192.168.1.100:2217
./ibus_tx tcp:192.168.1.100:2217
./joystick -p crsf /dev/input/event0 tcp:192.168.1.100:2217 -d

The client automatically negotiates baud rate, data size, parity, and stop bits using the Telnet COM-PORT-OPTION protocol. The 0xFF byte is transparently escaped/unescaped in the data stream. Modem and line state notifications are logged at debug level.

Testing with socat

Create a virtual RFC 2217 server that bridges to a local serial port:

socat TCP-LISTEN:2217,reuseaddr,fork FILE:/dev/ttyS0,raw,nonblock,waitlock=/tmp/s0.lock

Then connect from another machine:

./crsf_rx tcp:192.168.1.200:2217

Testing without hardware (loopback)

# Terminal A — RFC 2217 server (dummy)
socat -d -d TCP-LISTEN:2217,reuseaddr pty,raw,echo=0,link=/tmp/ttyV0 &

# Terminal B — generate CRSF frames
./crsf_tx /tmp/ttyV0

# Terminal C — receive via RFC 2217
./crsf_rx tcp:127.0.0.1:2217

Project structure

.
├── Makefile              — Build system
├── joycam.h              — Master header: CRSF + IBUS constants, structures, prototypes
├── joycam.c              — Shared utils: serial I/O, channel display, axis/button mapping
├── joycrsf.c             — CRSF protocol: CRC8, packet parser FSM, packet generator
├── joyibus.c             — IBUS protocol: checksum, packet parser FSM, packet generator
├── joyrfc2217.c          — RFC 2217 (Telnet COM Port Control): TCP client, IAC FSM, data escaping
├── joysbus.c             — SBUS protocol: termios2 baudrate, packet parser FSM, packet generator
├── crsf_rx.c             — CRSF receiver
├── crsf_tx.c             — CRSF transmitter
├── ibus_rx.c             — IBUS receiver
├── ibus_tx.c             — IBUS transmitter
├── sbus_rx.c             — SBUS receiver
├── sbus_tx.c             — SBUS transmitter
├── joystick.c            — evdev joystick reader with CRSF / IBUS / SBUS output
└── README.md             — This file

License

Copyright (c) OpenIPC https://openipc.org The Prosperity Public License 3.0.0

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JoyCam

Tools

Requirements

Cross-compilation for OpenIPC (arm-linux-gnueabihf / aarch64-linux-gnu)

Build

Usage

Receive CRSF data

Receive IBUS data

Receive SBUS data

Transmit test frames

Read joystick / full-chain bridge

Testing / Verification

Virtual serial port (no hardware required)

Full chain: joystick → receiver (loopback)

RFCP 2217 loopback (remote serial bridge)

Axis mapping (all protocols)

Button mapping (all protocols)

RFC 2217 (Serial-over-TCP) support

Testing with socat

Testing without hardware (loopback)

Project structure

License

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Name		Name	Last commit message	Last commit date
Latest commit History 43 Commits
LICENSE.md		LICENSE.md
Makefile		Makefile
NOTES.md		NOTES.md
README.md		README.md
crsf_rx.c		crsf_rx.c
crsf_tx.c		crsf_tx.c
ibus_rx.c		ibus_rx.c
ibus_tx.c		ibus_tx.c
joycam.c		joycam.c
joycam.h		joycam.h
joycrsf.c		joycrsf.c
joyibus.c		joyibus.c
joyrfc2217.c		joyrfc2217.c
joysbus.c		joysbus.c
joystick.c		joystick.c
sbus_rx.c		sbus_rx.c
sbus_tx.c		sbus_tx.c

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JoyCam

Tools

Requirements

Cross-compilation for OpenIPC (arm-linux-gnueabihf / aarch64-linux-gnu)

Build

Usage

Receive CRSF data

Receive IBUS data

Receive SBUS data

Transmit test frames

Read joystick / full-chain bridge

Testing / Verification

Virtual serial port (no hardware required)

Full chain: joystick → receiver (loopback)

RFCP 2217 loopback (remote serial bridge)

Axis mapping (all protocols)

Button mapping (all protocols)

RFC 2217 (Serial-over-TCP) support

Testing with socat

Testing without hardware (loopback)

Project structure

License

About

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