cyton-dongle

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# Cyton Dongle

USB wireless receiver (RFD22301/RFDuino) for OpenBCI Cyton 8/16-channel EEG board.

## Hardware

- **Dongle**: FTDI FT231X USB-UART → RFDuino 2.4 GHz radio
- **Serial**: 115200 baud, 8N1
- **Device**: `/dev/cu.usbserial-*` (macOS) or `/dev/ttyUSB*` (Linux)
- **Sample Rate**: 250 Hz
- **Channels**: 8 (Cyton) or 16 (Cyton + Daisy)
- **Packet**: 33 bytes (0xA0 start, 24 bytes channel data, 6 bytes aux, 1 byte counter, 0xC0 stop)

## First-Time Pairing (Critical)

A new dongle and board are typically on **different radio channels**. The standard `0xF0 0x01` channel-set command requires both sides to handshake — it **fails when they're on different channels**.

Use `0xF0 0x02` (CHANNEL_SET_OVERRIDE) to force the dongle to each channel without requiring board response, then check system status:

```python
import serial, time

ser = serial.Serial('/dev/cu.usbserial-XXXXX', 115200, timeout=2)
time.sleep(2)

for chan in range(26):
    ser.reset_input_buffer()
    ser.write(bytes([0xF0, 0x02, chan]))  # override dongle (no handshake)
    time.sleep(0.5)
    ser.read(ser.in_waiting or 512)

    ser.reset_input_buffer()
    ser.write(bytes([0xF0, 0x07]))        # system status query
    time.sleep(0.5)
    resp = ser.read(ser.in_waiting or 512).decode('utf-8', errors='ignore')

    if 'System is Up' in resp:
        print(f'FOUND BOARD ON CHANNEL {chan}')
        break
    else:
        print(f'Ch {chan}: Down')

ser.close()
```

## Radio Commands (0xF0 prefix)

| Bytes | Command | Notes |
|-------|---------|-------|
| `0xF0 0x00` | CHANNEL_GET | Returns current dongle channel |
| `0xF0 0x01 <ch>` | CHANNEL_SET | Coordinated change, **requires board online** |
| `0xF0 0x02 <ch>` | CHANNEL_OVERRIDE | **Dongle-only, no handshake** — use for pairing |
| `0xF0 0x03` | POLL_TIME_GET | Current poll time |
| `0xF0 0x04 <t>` | POLL_TIME_SET | Set poll time |
| `0xF0 0x05` | BAUD_DEFAULT | 115200 |
| `0xF0 0x06` | BAUD_FAST | 230400 |
| `0xF0 0x07` | SYS_STATUS | "System is Up" or "System is Down" |
| `0xF0 0x0A` | BAUD_HYPER | 921600 |

Channels are 0-25. Default for new boards is usually 1.

## Serial Commands

| Cmd | Action |
|-----|--------|
| `v` | Firmware version + board info |
| `b` | Start binary streaming |
| `s` | Stop streaming |
| `C` | Enable Daisy (16ch mode) |
| `D` | Query Daisy module |
| `?` | Print ADS1299 registers |
| `1`-`8` | Default channel settings (ch 1-8) |
| `!`-`*` | Default channel settings (ch 9-16, Daisy) |
| `d` | Reset all channel defaults |

## Parsing Binary Packets

```python
SCALE_UV = 4.5 / (24 * (2**23 - 1)) * 1e6  # ~0.02235 uV/count

def parse_24bit(b0, b1, b2):
    val = (b0 << 16) | (b1 << 8) | b2
    return val - 0x1000000 if val >= 0x800000 else val
```

**33-byte packet**: `0xA0 | sample_num | 8×3-byte channels | 6-byte aux | 0xC0`

With Daisy: odd sample numbers = channels 1-8, even = channels 9-16.

## Streaming and Channel Quality Check

```python
import serial, time, math

ser = serial.Serial('/dev/cu.usbserial-XXXXX', 115200, timeout=5)
time.sleep(2)
ser.reset_input_buffer()

# Override to known channel
ser.write(bytes([0xF0, 0x02, CHANNEL]))
time.sleep(1)
ser.read(ser.in_waiting or 512)

# Reset board
ser.write(b'v')
time.sleep(3)
ser.read(ser.in_waiting or 4096)
ser.reset_input_buffer()

SCALE_UV = 4.5 / (24 * (2**23 - 1)) * 1e6

def p24(b0, b1, b2):
    v = (b0 << 16) | (b1 << 8) | b2
    return v - 0x1000000 if v >= 0x800000 else v

# Start stream
ser.write(b'b')
time.sleep(1.5)
ser.read(ser.in_waiting or 2048)  # drain text

From plurigrid/asi, MIT.

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