Wearable BCI Design Discussion

flux

0:00

Work done
  • SWD programming: verified existing 2x3 SWD header PROG is wired to U3 on nets SWDIO, SWDCLK, 3V3_D, and GND.
  • BQ25895 support: added the required 47 nF BTST bootstrap cap C5 between U4 BTST and SW; verified the JST-PH 2-pin battery connector J4 is connected to BAT and GND; verified SYS from U4 feeds both LDO1 IN and LDO2 IN.
  • Dual-LDO isolation: ensured LDO1 serves the 3V3_D rail (MCU/USB) and LDO2 serves the 3V3_A rail (analog); connected 3V3_A to U2 AVDD1 and added C6 (SYS input decoupling) and C7 (3V3_A output decoupling).
Placement prep (manual guidance)
  • Quiet Zone (9:00): place J1 on the left edge; put D1/D2 between J1 and U2; place U2 immediately to the right of J1.
  • Noisy Zone (3:00): place J2 top-right; place U4 + L1 just below J2; place battery connector J4 adjacent to U4.
  • Bridge Zone (6:00): place U3 bottom-center/right; place PROG along the bottom edge.
  • Decoupling proximity rule: move each IC’s local decouplers (e.g., C5, C6, C7, C1, C2) to be as close as physically possible to the corresponding power pins.
Routing handoff (deferred)
  • Plan: bottom-layer GND pour; top-layer 0.5 mm power trunk; keep top-layer sensor inputs as short as possible; route SPI on bottom layer.
Success criteria review
  • ✅ SWD header added/connected to U3
  • ✅ BQ25895 improvements implemented: C5, J4, SYS->both LDOs
  • ✅ Dual-LDO isolation implemented with distinct 3V3_D and 3V3_A
  • ✅ Placement-zone guidance provided (Quiet/Noisy/Bridge) + decoupling proximity guidance
  • ✅ Routing guidance documented; routing intentionally deferred
Next steps
  • I cannot auto-place or auto-route. After you place parts, run Auto-Layout for routing and I will re-check airwires/DRC and iterate placement tweaks if needed.
72 days
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    8-Channel Wearable BLE5 Brain–Computer Interface with 24-bit Biopotential AFE and Cross-Platform SDKs

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"Power Subsystem"
"Biopotential AFE/ADC"
"BLE MCU/SoC"
"Electrode Connector"
"Status LEDs"

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