braincom.linker
Why this exists
Research-grade multichannel EEG hardware is expensive and closed. Adam-EEG set out to prove that a 32-channel, simultaneous-sampling, standalone-logging EEG acquisition board could be built from commodity parts, in a hobbyist CAD tool, at a fraction of the cost — fully open, so anyone can build on it rather than starting from a datasheet.
Technical specifications
| Analog front end | 4 × Texas Instruments ADS1299 — 24-bit, 8-channel, simultaneous-sampling, low-noise biopotential ADC |
| Total channels | 32 unipolar channels + common reference, fully simultaneous (no muxing) |
| AFE interconnect | Multi-device SPI daisy-chain — shared SCLK/DIN/DOUT/DRDY, individual CS1–CS4 per ADS1299 |
| Controller | 2 × ATmega328 (SMD, Arduino-compatible core) |
| Programming | 2 × 6-pin AVR ISP headers |
| Onboard storage | microSD socket — standalone data logging, no host PC required |
| Power | Onboard bipolar analog rail generation: LM2663 switched-capacitor inverter + LP5907 / TPS723xx LDOs |
| Board | 2-layer, 97.2 × 81.9 mm (~79.6 cm²), 2 × Ø3.2 mm mounting holes |
| Complexity | 354 schematic parts / 229 placed board elements |
| CAD format | EAGLE 6.6.0 XML (.sch / .brd) — single schematic sheet |
| License | Apache License 2.0 |
Connectors & pinout
Extracted directly from the schematic's named nets:
- ARDUINO_CONN (1×11): full SPI daisy-chain + control breakout — CS1–CS4, SCLK, DIN, DOUT, DRDY, RST, PD, STRT — lets an external Arduino-compatible host drive all 4 ADS1299 directly.
- ELECTRODES_P&N (1×18): primary differential electrode input header.
- ELECTRODES / ELECTRODES1 / ELECTRODES2 (3× 1×8): buffered per-channel output/test points for 3 of the 4 ADS1299s.
- POWER_PIN (1×2): +5V / AGND main power input.
- JP3–JP5: in-line jumpers on the SPI DIN/DOUT/SCLK lines.
System architecture
Each ADS1299 samples 8 channels simultaneously; the four devices share one SPI bus in TI's standard multi-device daisy-chain topology (DOUT of one feeds DIN of the next), so all 32 channels are read out in lockstep with no channel-to-channel skew. The dual ATmega328 controller manages the chain and streams data to the onboard microSD card for fully standalone logging — no host PC required for a recording session.
Safety & disclaimer
This is an open-hardware research/prototyping board, not a certified medical device. It has not undergone FDA/CE or equivalent regulatory clearance, and no formal patient-isolation or leakage-current certification has been performed. Power it only from isolated, battery-backed supplies — never connect a build to mains-powered equipment while it is attached to a person.
Full source
Complete EAGLE schematic + board files, a detailed README (with the connector pinout table and a passive-component reference derived straight from the netlist), and contribution guidelines are all in the GitHub repo: github.com/shiva16/Adam-EEG