📡 What is SBUS? — Simple Explanation
SBUS (Serial Bus) is a digital protocol used in RC systems to send multiple control signals (channels) over a single wire.
🧩 Key Features
- 🔢 Up to 16 channels in one signal
- 💬 Digital serial protocol
- 📦 Sends data in serial frames
- ⏱️ 100,000 baud, inverted UART
- ↪️ Invented by Futaba, widely used (FrSky, Radiolink, etc.)
- 🧠 Needs inversion to be read by normal UART (hardware or software)
🧱 Simple Analogy
SBUS is like 16 people taking turns speaking very fast on one microphone.
Each frame contains all channel values packed tightly together.
🧪 Data Frame Structure
Each SBUS frame is 25 bytes:
| 1 byte | 22 bytes | 1 byte | 1 byte |
|---|---|---|---|
| Header | 16 channels | Flags | End |
- Header: 0x0F
- End: 0x00
- Sent every ~9ms (111Hz refresh rate)
🔌 Common Use Cases
- RC Receiver → Flight Controller (e.g., FrSky RX to Betaflight FC)
- RC Receiver → Microcontroller (Arduino, ESP32)
- RC → Servo controller boards (if SBUS supported)
⚖️ SBUS vs PWM vs PPM
| Feature | SBUS | PWM | PPM |
|---|---|---|---|
| Channels | 16 | 1 per wire | 8 (typically) |
| Wires needed | 1 | 1 per channel | 1 |
| Type | Digital | Analog pulse | Analog pulse |
| Speed | Very fast | Slow | Medium |
| Latency | Very low | High | Medium |
🧰 Tip for Developers
To read SBUS using a microcontroller:
- Use UART at 100000 baud, 8E2, inverted signal
- Some MCUs (like ESP32) support inversion natively
- Otherwise, use an inverter circuit or a software decoder