Live Lab (Bio-Pen): Shareable Live Biosignal Pipelines in a Single URL

Live Lab (Bio-Pen) is now live in PiEEG Cloud at cloud.pieeg.com/lab.

Open the URL to run a chain of JavaScript stages at 15 ticks per second against a 2-second 250 Hz multichannel ring buffer from a connected PiEEG board (Web Bluetooth, Web Serial, or pieeg-server WebSocket). When no hardware is connected, /lab boots directly on the built-in 8-channel simulated stream so any shared link runs immediately.

Reactive stage pipeline

User code executes inside a dedicated Web Worker. Stage 1 receives the live frame (win, EEG, bands, focus, relax, dataset, fs). Each following stage receives the previous stage's return value as input.

Every stage plots its return value automatically on the right-hand instrument canvas:

Scalar (number or { value, unit }): readout and 120-tick rolling sparkline.
1D array (<= 16 items): bar chart across channels or features.
1D array (> 16 items): time-domain waveform trace with zero-line and peak amplitude in µV.
Spectrum ({ freqs, power, peakHz }): Hann-windowed power spectral density with the 8-12 Hz alpha band marked.
Matrix (number[][] or { labels, matrix }): 2D heatmap for covariance or confusion matrices.
Decoder ({ label, probs, loroBalancedAccuracy }): live class probability bars and held-out accuracy badge.

Clicking Freeze 2s Window captures the current 2-second multichannel window and feeds that exact buffer on every tick so you can edit and debug DSP or feature code deterministically before returning to the live stream.

Built-in DSP, classifiers, and LORO-CV

The worker scope provides pure TypeScript numerics without external backend dependencies:

Spatial and time-domain: car(win) (Common Average Reference), bipolar(chA, chB), detrend, zscore, mean, std, variance, rms, lineLength, slopeSignChanges, cohensD.
Spectral: fft(sig), psd(sig, fs, maxHz), bandpower(sig, [lo, hi], fs).
Classifiers and cross-validation: lda(X, y, shrinkage) (Ledoit-Wolf Shrinkage-LDA), logreg(X, y) (L2 multinomial logistic regression), crossValScore(X, y, k), and loroCV(X, y, reps, kind) (Leave-One-Rep-Out cross-validation).

The Session Dataset bar records 2-second labelled epochs from the live stream (or seeds a 12-trial reference dataset) and groups samples by repetition index. In the Decoder Arena, your active pipeline decoder is benchmarked side by side against reference Shrinkage-LDA and L2 Logistic Regression models, showing both trial-grouped LORO-CV balanced accuracy and naive sample-split k-fold accuracy so temporal autocorrelation leakage is visible.

Graded briefs and one-click Bio-Pen sharing

Graded Briefs: Select a brief from the header to run live check(condition, message) assertions against your pipeline output and session dataset.
Save, Fork, and Share (Ctrl+S): Saving mints a /lab/:id URL and copies it to the clipboard. Guest creators receive a local cryptographic edit token (X-Pen-Token) so they can update or delete their own pen without an account; anyone else who opens the link and saves creates a forked /lab/:newId.
OSC Output: Enable the Local Bridge toggle to stream the final stage's numeric or probability outputs to /pieeg/lab/* over WebRTC P2P.

Limits

Within-session Cohen's d and LORO-CV balanced accuracy describe separation within the current electrode placement and session; they are not cross-subject or cross-day generalisation claims.
Frontal channels (Fp1/Fp2) carry large corneal-retinal EOG (100-400 µV) and facial sEMG above 20 Hz. Always inspect the time-domain waveform alongside spectral ratios.