Octopus 16 packs sixteen EEG electrodes, a common reference, and a ground into a single 26 mm circular PCB — a coin-sized cluster of spring-loaded pogo pins. Because reference and ground live inside the same footprint as the active channels, no distant electrodes are required: the whole montage sits locally on the scalp and streams 16-channel data over Bluetooth Low Energy 5 to a host, a USB dongle, or straight to the browser.
On the PiEEG Shop
How to start YouTube Demo
3D printer Box in Thingiverse
Octopus included in PiEEG-Server software, Docs is here
YouTube video
Warning
Octopus_16 is not medical device. You are fully responsible for your personal decision to purchase this device and, ultimately, for its safe use. Octopus_16 is not a medical device and has not been certified by any government regulatory agency for use with the human body. Use it at your own risk. [!CAUTION] The device must operate only from a battery - 5 V. Complete isolation from the mains power is required.! The device MUST not be connected to any kind of mains power, via USB or otherwise. Power supply - only battery 5V, please read the liability
16 Ch Data transfer - BLE 250 samples per second Connect ESP-32C6 to the data transfer
| Parameter | Value |
|---|---|
| ADC | 2 × Texas Instruments ADS131M08 |
| ADC type | 24-bit, 8-channel, simultaneous-sampling, delta-sigma (ΔΣ) |
| Channel count | 16 (8 per ADC) |
| Resolution | 24-bit per channel (transmitted as 3 bytes / channel) |
| Programmable gain (PGA) | Per-channel, ×1 – ×128 (set in firmware; default gain register 0x2222) |
| Input high-pass / DC block | Integrated ADC DC-block filter enabled (≈ >1 Hz) |
| ADC interface | SPI (shared bus; independent chip-select per ADC, shared RESET, single DRDY from ADC 1 as sync master) |
| Clock source | External SMD oscillator, EuroQuartz XO32 series (3.2 × 2.5 mm), 8.192 MHz |
| Oversampling ratio (OSR) | 16384 |
| Output data rate | 250 SPS — f_CLKIN / (2 × OSR) = 8.192 MHz / (2 × 16384) |
| Parameter | Value |
|---|---|
| Contact type | Spring-loaded pogo pins, ⌀4 × 11 mm SMD |
| Total pins | 18 |
| → Active signal (+) | 16 channels |
| → Reference (−) | 1 (common AINREF) |
| → Ground | 1 (GND) |
| Pin pitch (center-to-center) | ≈ 5.38 mm (uniform hexagonal packing; measured min 5.37 / max 5.39 mm) |
| Array span | ≈ 20.3 × 20.3 mm, all pins within a ~10.5 mm radius of center |
| Reference / ground routing | Selectable via on-board jumpers (AINREF_POGOPIN_ON, AINREF_STACK_ON, GND_ON, STACK_1/2) for stacking or single-board use |
| Parameter | Value |
|---|---|
| Form factor | Circular PCB, 26.0 mm diameter |
| Layers | 4-layer (F.Cu / In1.Cu / In2.Cu / B.Cu) |
| Target placement | Pz (parietal); works as a fully local montage anywhere on the scalp |
| Enclosure | 3D CAD included (p70-2100045, IGS + STP) |
| Parameter | Value |
|---|---|
| Main module | Seeed Studio XIAO ESP32-C6 (RISC-V, BLE 5) |
| Alternate build | XIAO ESP32-S3 variant (adds native USB / BLE HID gamepad output for neurofeedback control) |
| Radio | Bluetooth Low Energy 5, 2M PHY, TX power +3 dBm |
| Data packet | 51-byte custom frame: 0xA0 header + 1-byte counter + 24 B (ADC1) + 24 B (ADC2) + 0xC0 footer |
| Throughput layout | 16 channels × 3 bytes = 48 signal bytes per sample |
Place the 18-pin cluster over Pz (or your target site) with firm, even contact. Because reference and ground are inside the same cluster, no additional electrodes are needed. Good scalp contact on all pins is the single biggest factor in signal quality.