A 26 mm (1.0 inch) diameter circuit board with 16 electrodes and a pair of 24-bit ADCs is all it takes to turn a Seeed XIAO ESP32-S3 into a wireless brain-controlled gamepad. The Octopus 16, the latest device from the PiEEG project, captures EEG, EMG, and ECG biosignals through 18 spring-loaded pogo pins and streams them over Bluetooth Low Energy as standard HID input, letting users navigate games with nothing but neural activity. Because the device presents as a generic BLE HID gamepad, Linux pairs with it via BlueZ without custom drivers. The software stack, including Arduino firmware and a Python-based PiEEG server, is fully open source.
Under the hood, two Texas Instruments ADS131M08 delta-sigma ADCs sample all 16 channels simultaneously at up to 16,000 samples per second with programmable gain from x1 to x128. The four-layer PCB fits its entire electrode array within a roughly 10.5 mm radius, with reference and ground routing selectable via onboard jumpers for single-board or stacked configurations. Power comes from USB-C through the host XIAO board, so running the whole setup off a small power bank is straightforward. A 3D-printable enclosure rounds out the build.
The PiEEG server runs natively on Linux, macOS, Windows, and Raspberry Pi, and installs via pip or a single curl command, requiring Python 3.10 or later. It streams all channels as plain JSON over WebSocket on port 1616, with a browser dashboard on port 1617. The protocol uses no proprietary SDK or binary framing, so any language or tool with WebSocket support can consume the biosignal stream directly.
PiEEG, led by researchers Ildar Rakhmatulin and Youssef El Abbass, has been iterating on affordable open-source BCI hardware for several years, from a Raspberry Pi EEG shield to an Arduino UNO R4 WiFi add-on. The Octopus 16 is the most compact entry yet, and the team is also expanding into VR with a Quest facial interface that aims to translate brain signals and micro-expressions into avatar control. An online demo lets anyone try the signal-processing pipeline in a browser without hardware.
A video demo shows a developer navigating a maze purely through thought. The results are functional but visibly labored, making it clear that EEG-based input is still a long way from replacing a mouse and keyboard for anything fast-paced. The Octopus 16 sells for $250 (€230), and buyers will need to add a XIAO ESP32-S3 or ESP32-C6 board and a battery separately.
