Convey

CONVEY (open 8-channel EEG · sEMG · ECG acquisition board)

CONVEY is an open-hardware, patient-isolated, general-purpose biosignal front end: eight 24-bit differential channels around the TI ADS1299, on a 64 × 64 mm 4-layer board that records EEG, surface EMG or ECG depending only on configuration and electrode montage. It runs from a 5 V USB power bank, isolates the subject from the host to 5000 V_RMS (reinforced), cancels mains interference in hardware with an active bias drive, and carries a 6-axis IMU clock-locked to the ADC's oscillator so motion and biosignal share one time base. Any microcontroller drives it over a 15-pin SPI header; a reference ESP32-S3 firmware is included.

It exists because an 8-channel OpenBCI Cyton costs ≈ ₱70 000+ (16 channels ≈ ₱140 000+) in the Philippines before shipping, import and electrodes (the store's own peso prices on 23 August 2026 were ₱78,200.00 and ₱156,500.00; a feature-by-feature comparison is in the tech report §2, Table 1). CONVEY is the accessible alternative, and a fully documented instrument, so the acquisition chain itself can be studied as well as used.

The name is the job: to convey is to carry something from one place to another and to communicate what is felt. The body produces its messages as microvolt signals in the brain, heart and muscles; this board carries them across the isolation barrier, cleanly and safely, to where they can be read.

Status : design-verified and fab-ready; not yet fabricated. DRC 0 errors / 0 unconnected · 56/56 automated design gates · isolation barrier verified on the Gerbers · ERC 0 · two ground-up adversarial design reviews with every finding closed · BOM with live-verified LCSC stock. Fabrication + assembly + shipping to the Philippines is 2-3 weeks; the first article is ordered the week after Reverie Hacks 2026. Details: docs/TECH_REPORT.md §11. All performance figures below are datasheet / design values, not measurements.

Submitted to Reverie Hacks 2026, Embedded Systems track.

Where the isolation barrier is

The highlighted band (board y 60 to 68 mm) is a rule area that forbids tracks, vias, pads and pours on every layer. The host side (J1 header, IMU, input protection) sits above it, the patient side (ADS1299, electrodes, reference, clock, regulators) below it, and only the isolated DC/DC converter and the two digital isolators straddle it. The band is checked three times: in the netlist (every net is single-sided), in the KiCad rule area, and on the Gerber files by verify_gerber_barrier.py. The board's own design note on the comments layer marks it; the KiCad editor view is in hardware/images/pcb_layout_editor.png. Why there is no physical board yet, and what stands in for one: docs/TECH_REPORT.md §11.

Key specifications (design values)

Repository map

Open it

1. Install KiCad 10 (10.0.1 or later). Open hardware/kicad/CONVEY.kicad_pro. Project libraries resolve through ${KIPRJMOD}; stock symbols/footprints/3D models come from the KiCad installation.
2. If KiCad 10.0.1 shows a "Library … not found in library table" dialog on open, click OK, it is a known cosmetic race in that release; nothing is missing.
3. 3D view: PCB editor → Alt+3.

Verify it (the gates the design ships with)

From hardware/kicad/, using KiCad's Python (Windows path shown; adjust for your OS):

"C:/Program Files/KiCad/10.0/bin/python.exe" verify_board.py --drc

→ 56 checks (geometry, 8 mm barrier on all layers, netlist↔board, footprint/3D resolution, track-width convention, net classes, DRC wrapper), expect 56 passed, 0 failed, 0 errors, unconnected items: 0.

"C:/Program Files/KiCad/10.0/bin/python.exe" verify_gerber_barrier.py

→ parses the actual Gerber/Excellon files in hardware/fab/gerbers/ and proves no copper, pour or hole lies in the barrier band on any layer, expect BARRIER ON THE PLOTS: CLEAN.

Order it

hardware/fab/README_ORDERING.md: JLCPCB 4-layer, 64 × 64 mm, 1.6 mm, ENIG recommended; upload CONVEY_gerbers.zip, CONVEY_bom_jlcpcb.csv, CONVEY_cpl_jlcpcb_top.csv. Six lines are external-source parts (listed there). Then follow hardware/docs/10_bringup_plan.md, every step has an expected value.

Reference firmware

firmware/README.md: ESP32-S3 (Arduino-ESP32 3.3), wiring table for J1, the bring-up sequence (power-up → reset → ID 0x1E → CONFIG1/2/3 → CHnSET → START → RDATAC), DRDY-driven 27-byte frames, IMU on the 32 kHz CLKIN, CSV/binary serial output. It compiles; it has not run on hardware because the hardware does not exist yet. Flowchart: firmware/docs/FLOWCHART.md.

What is not in this repo

Third-party datasheets (listed with SHA-256 in hardware/docs/DATASHEETS.md), vendored reference projects (linked in REFERENCES.md), KiCad stock libraries, the design's working snapshots and backups, and internal working notes.

Licenses

Hardware: CERN-OHL-S v2 (LICENSE). Firmware, software and scripts: MIT (LICENSE-MIT). See LICENSING.md. CONVEY is a research/educational design, not a medical device.