Specification
Hardware
| Channels | 8 (PiEEG XR) or 16 (PiEEG XR-16, depending on version) |
| Extra inputs | Reference and bias |
| Analog front end | Texas Instruments ADS1299, 24-bit (dual ADS1299 on 16-channel versions) |
| Sample rate | 250 SPS |
| Noise | 1.0 µV peak-to-peak |
| Microcontroller | STM32WB series: dual-core Arm Cortex-M4 (application) and Cortex-M0+ (radio stack) |
| Wireless | Bluetooth Low Energy 5 |
| Power | 5 V over USB-C, from a power bank or a battery head strap |
| Programming | SWD header (GND, RST, SWDIO, SWCLK) inside the box, for an ST-Link |
Mask and electrodes
| Electrodes | 10 flat dry Ag/AgCl: 8 channels, reference, bias |
| Electrode type | Dry; also works with gel or saline |
| Positions | Forehead and temples (see Mask & Electrodes) |
| Mask material | Silicone |
| Fit | Made for one headset model (Meta Quest 3, Meta Quest, PICO and others). Clips in with four buckles, or use the silicone insert alone. |
Software support
| Software | Setting |
|---|---|
| BodyPress | Meta Quest (opens in a new tab) and Android (opens in a new tab) |
| PiEEG Cloud | PiEEG Devices → PiEEG XR / PiEEG XR-16 |
| PiEEG Server | --device ironbci8 (8 channels) |
| VRChat OSC | pieeg-server --device ironbci8 --osc |
Bluetooth data format
PiEEG XR uses the same Bluetooth protocol as IronBCI:
| Advertised name | PiEEG XR |
| Data characteristic (notify) | 0000fe42-8e22-4541-9d4c-21edae82ed19 |
| Sample | 8 channels × 3 bytes, 24-bit big-endian two's complement. A notification can carry one or more samples. |
Converting to microvolts, as PiEEG Server does:
raw = (b[0] << 16) | (b[1] << 8) | b[2]
if raw & 0x800000:
raw -= 1 << 24
uV = raw * 4.5 / 16777215 * 1e6Full details and example code: IronBCI specification.
Raw values carry a large DC offset (thousands of µV) from the electrode contact. That is normal. Apply a band-pass filter (for example 1–40 Hz) before looking at the signal.