Electrodes & Pinout
Electrode connections
JNEEG has three kinds of electrode inputs.
| Input | Count | Electrode | Purpose |
|---|---|---|---|
| Channels 1–8 | 8 | Dry or wet Ag/AgCl, in the cap | Each channel measures the voltage between its electrode and the reference |
| Reference | 1 | Ear clip on one earlobe | The common 0 µV point that all 8 channels are measured against |
| Bias | 1 | Ear clip on the other earlobe | Actively drives the body to cancel common-mode noise such as 50/60 Hz mains hum |
The electrode header is a standard 2.54 mm pin header (marked 1-8 Elec), so most EEG cables with 2.54 mm female connectors fit. See Cap.
The reference and bias clips matter most. A loose ear clip makes every channel noisy at once. Clean the earlobes and make sure both clips sit firmly.
Suggested montage
Place the electrodes on the 10-20 system. This layout is the same as the PiEEG-8 default, so recordings can be compared:
| Channel | Position | Area | Good for |
|---|---|---|---|
| 1 | Fp1 | Front left | Blinks, eye movement |
| 2 | Fp2 | Front right | Blinks, eye movement |
| 3 | C3 | Centre left | Motor activity (right hand) |
| 4 | C4 | Centre right | Motor activity (left hand) |
| 5 | P7 | Back left, side | Parietal and temporal activity |
| 6 | P8 | Back right, side | Parietal and temporal activity |
| 7 | O1 | Back left | Alpha rhythm, vision |
| 8 | O2 | Back right | Alpha rhythm, vision |
You can use any other positions. Keep a note of which channel went where.
Jetson Nano pinout
The shield talks to the Jetson Nano over SPI (spi1 in jetson-io, which appears as /dev/spidev0.0). It uses these pins on the 40-pin header:
| Header pin | Signal | Direction |
|---|---|---|
| 19 | SPI MOSI | Jetson → ADS1299 |
| 21 | SPI MISO | ADS1299 → Jetson |
| 23 | SPI SCK | Jetson → ADS1299 |
| 24 | SPI CS0 (chip select) | Jetson → ADS1299 |
| 7 | DRDY (data ready) | ADS1299 → Jetson |
The shield also takes its power and ground from the header.
DRDY goes low each time a new sample is ready (250 times per second). The Python scripts read it as board pin 7 with Jetson.GPIO. PiEEG Server reads it as line 216 on /dev/gpiochip0.