USB C Sensor Node
Worked for 1 min 56 sec
Built the schematic for a USB-C powered Wi‑Fi/BLE temperature + humidity sensor node using ESP32‑C3‑MINI‑1‑N4, SHT40, TPS25940 eFuse protection, MP28301 3.3 V buck regulation, USB-C CC pull-downs, USB data ESD, VBUS TVS, reset/boot controls, status LED, and test pads. I also created the key project files: Project Specification, Power Budget and Design Notes, Firmware Starter, Board Bring-Up Plan, and Technical Construction File.
Open items:
- I’m blocked from continuing because your account currently has no available ACUs, so AI tools are unavailable.
- Full check results show expected PCB airwires because layout/routing has not been done yet.
- Several generic passives/testpoints still need final manufacturer part numbers before manufacturing export.
- Layout still needs antenna keepout, SHT40 thermal isolation, USB-C ESD placement, and buck-regulator power-loop placement.
Suggested next steps:
- Refill/enable ACUs, then ask me to finish verification and clean remaining manufacturing metadata.
- Proceed to PCB placement with ESP32 antenna edge keepout and isolated SHT40 placement.
- Route the board, then run DRC/ERC again.
- Lock exact passive/inductor MPNs and generate manufacturing files.
Verify, layout, export
Finish verification
Place components
Route and review
Lock MPNs
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Technical Construction File — USB-C WiFi T-RH Sensor Node
Status
Draft — schematic stage, pre-layout.
Applicable Regulations / Programs
- FCC Part 15 intentional radiator and unintentional radiator requirements.
- CE RED / EMC / RoHS as applicable for EU sale.
- ISED Canada if sold in Canada.
- UKCA if sold in the UK.
- USB-IF only if using USB logos or claiming formal USB compliance.
- RoHS / REACH material compliance.
- WEEE obligations depending on market.
Product Description
USB-C powered consumer environmental node measuring temperature and relative humidity and reporting via Wi-Fi and BLE. The design uses an Espressif ESP32-C3 module with integrated antenna and a Sensirion SHT40 digital sensor.
Wireless Technology Summary
Table
| Module | MPN | Technology | Frequency Band | Antenna | Pre-certification Status |
|---|---|---|---|---|---|
| U1 | ESP32-C3-MINI-1-N4 | 802.11 b/g/n Wi-Fi + BLE 5.x | 2.4 GHz ISM | integrated PCB antenna | Use Espressif module certification documentation; final status must be verified for exact module revision and market. |
Current BOM Evidence
Table
| Designator | MPN | Manufacturer | Regulatory Relevance |
|---|---|---|---|
| U1 | ESP32-C3-MINI-1-N4 | Espressif | Radio module and antenna integration rules. |
| J1 | USB4215-03-A | GCT | USB-C connector. |
| U3 | TPS25940LRVCR | Texas Instruments | Input protection / safety robustness. |
| U4 | MP28301GG-P | Monolithic Power Systems | Switching regulator / EMC source. |
| U2 | SHT40-AD1B-R2 | Sensirion | Sensor exposed to environment. |
| D1 | ESD5341N | TECH PUBLIC | USB VBUS ESD protection. |
| D2 | USBLC6-2SC6 | UMW | USB D+/D− ESD protection. |
RF Design Notes
- Use the ESP32-C3-MINI-1-N4 module as a module, not a bare RF IC.
- Place antenna at PCB edge and follow Espressif keepout requirements exactly.
- Keep copper, ground pours, traces, vias, shields, batteries, metal, and tall components out of the antenna keepout on all layers.
- Do not place the USB-C shield, regulator, inductor, or SHT40 in the antenna keepout.
- Final enclosure materials and nearby metal/plastic must be checked against module integration requirements.
EMC / ESD Design Notes
- D1 clamps VBUS to GND near the USB-C input.
- D2 protects USB_DP and USB_DM near the connector.
- TPS25940 provides controlled inrush/current limiting and fault protection.
- MP28301 buck layout must keep SW loop compact; final layout should avoid routing near antenna and SHT40.
- USB shield is tied to board ground in this schematic; final ESD/EMC testing may require adjustment.
Required Documentation Checklist
- Schematic draft in Flux.
- Current BOM evidence table in this file.
- Product block description in Project Specification.
- Preliminary RF integration notes in this file.
- Bring-up validation plan.
- Final PCB layout / Gerbers after layout stage.
- Final BOM with distributor and lifecycle review.
- Espressif module grant/FCC ID/CE documentation for exact module revision.
- User manual and labeling with required RF statements.
- Accredited EMC/RF test reports.
- Final Declaration of Conformity signed by responsible party.
Draft Declaration of Conformity Text
We, [Company / Responsible Party], declare that the product USB-C WiFi T-RH Sensor Node is designed as a USB-powered temperature and humidity monitoring device using a certified 2.4 GHz Wi-Fi/BLE radio module. Final conformity depends on successful completion of product-level EMC/RF testing, final module certification evidence, production BOM control, and required labeling.
Authorized signatory: ____________________
Date: ____________________
Open Items / Action Required
- Verify exact ESP32-C3-MINI-1-N4 certification IDs and allowed antenna/integration conditions.
- Complete PCB layout with documented antenna keepout.
- Review enclosure for RF detuning, airflow, ESD access, and sensor accuracy.
- Complete EMC pre-scan before production tooling.
- Prepare final user manual/label statements before consumer sale.
Status
Applicable Regulations / Programs
Product Description
Wireless Technology Summary
Current BOM Evidence
RF Design Notes
EMC / ESD Design Notes
Required Documentation Checklist
Draft Declaration of Conformity Text
Open Items / Action Required
