ESP32-C3 Multi-Board Design

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Placed 36 component(s): C7, C1, J4, U2, C14, C2, C3, R4, C4, U1, L1, J9, C12, J6, C11, D1, R2, R7, R5, R3, J8, U4, J5, J3, R6, J7, C6, C5, J10, U5, J2, U3, F1, R1, J1, C13

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Work done
  • Updated the schematic into a dual-board stack concept: primary board keeps ESP32-C3, TMP117, LIS2DW12, and J8; secondary board carries LiPo charging/power, pogo access, external antenna interface, and J9/J10.
  • Added and wired the J8/J9 board-to-board interconnect and J10 U.FL antenna interface; core ERC checks are passing.
  • Reconfigured the PCB into a two-board 28 mm-wide stack/panel representation and re-placed the components into primary/secondary clusters.
  • Documented the partition, interconnect pinout, verification state, and manual-routing priorities in Two-Board Stack Revision.
Success criteria review
  • ✅ Dual-board partition defined and reflected in schematic/component roles.
  • ✅ Core functions preserved: ESP-NOW MCU, TMP117, LIS2DW12, LiPo charging/power, and pogo access remain connected.
  • ⚠️ Layout de-risked but not fully clean: missing footprints and ERC checks pass, but remaining physical-layout issues still need routing/layer cleanup before fabrication.
Next steps
  • Refresh/regenerate routing for the new two-board placement, then clear the remaining physical layout issues before manufacturing export.
Check DRC issues
Export assembly files
Show interconnect pinout
Document routing priorities
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Files

Schematic

Layout

Preview

Design Notes
External Antenna Revision
This revision changes the wireless module from ESP32-C3-MINI-1-N4 to ESP32-C3-MINI-1U-N4 so the compact sensor node can support an external antenna without adding a separate RF cable-launch footprint.
Key decision
  • Use the module variant with the integrated external antenna connector.
  • This preserves the existing ESP32-C3 / ESP-NOW architecture while avoiding a fragile extra RF transition inside the already crowded 28 mm circular board.
RF / mechanical implications
  • Keep U1 near the top edge for practical antenna-cable access.
  • Avoid placing dense circuitry immediately in the connector access direction.
  • Preserve the thermal sensing region around U2 near the board center.
  • Keep the switching power stage grouped away from the thermal contact area.
Functional signals preserved after module swap
  • I2C: IO4=SDA, IO5=SCL
  • TMP117 alert: IO1
  • LIS2DW12 interrupt: IO0
  • Charger status: IO6
  • Boot strap: IO9
  • UART programming / debug: TXD0, RXD0
Compactness Revision for Single-Board Feasibility
To improve the odds of keeping the design on a single 28 mm circular, 4-layer board, the access hardware was reduced in footprint while preserving functionality.
Connector and contact changes
  • Replaced the battery connector J1 from S2B-PH-SM4-TB(LF)(SN) to SM02B-GHS-TB(LF)(SN).
  • This reduces the battery connector pitch from 2.0 mm to 1.25 mm while still keeping a locking wire-to-board battery interface.
  • Replaced the six large pogo targets J2-J7 with 1.25 mm SMD Test Point parts for denser fixture access.
Preserved access functions
  • J2 = POGO_5V_IN
  • J3 = GND
  • J4 = UART_TX_POGO
  • J5 = UART_RX_POGO
  • J6 = ESP_EN
  • J7 = BOOT
Practical layout result
  • Component area dropped substantially after the connector/test-pad reduction.
  • The board moved from a clearly overpacked state toward a more workable compact layout.
  • The power section still needs careful routing discipline because the switching/power cluster remains dense in the lower-right quadrant.
  • The ESP32-C3 module, center thermal sensor region, motion sensor, battery connector, and pogo access can all coexist on the 28 mm outline in placement, but trace completion remains the final proof.
Remaining layout considerations
  • Bottom-edge pogo access and short UART/ESD routing should be prioritized during final trace routing.
  • The external antenna cable path should be kept clear of the battery and switching power loop.
  • If final routing around U1 and the pogo/ESD entry still proves impractical, the fallback should be a stacked architecture that moves RF access to a dedicated board while leaving sensing/power on the main board.

  • External Antenna Revision

  • Key decision

  • RF / mechanical implications

  • Functional signals preserved after module swap

  • Compactness Revision for Single-Board Feasibility

  • Connector and contact changes

  • Preserved access functions

  • Practical layout result

  • Remaining layout considerations