Temperature and Humidity Sensor Node Design
continue
Thought for 3 sec
I’ll inspect the current schematic and project docs, run design checks, then fix any schematic issues I find before summarizing what remains for layout.
Worked for 52 sec
I’m blocked because the account has no available ACUs, so I can’t continue AI layout actions right now.
Completed this session:
- Verified the schematic/ERC state: no open errors or warnings were reported.
- Set up the PCB as a 45 mm × 30 mm rounded rectangle with a standard 4-layer stackup and 0.5 mm board keepout.
- Confirmed the board area is workable, though routing may be tight around the ESP32/power section.
Remaining work:
- Place components with ESP32 antenna keepout, USB-C edge placement, compact buck/eFuse layout, and isolated SHT41 placement.
- Route the PCB.
- Run DRC and airwire checks.
- Fix any routing or layout violations before manufacturing export.
Review placement constraints
Check ACU balance
Run layout checks
Estimate board size
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Project Specification — USB-C WiFi BLE Environmental Sensor Node
Purpose
Consumer USB-C powered environmental node measuring temperature and relative humidity, reporting over Wi-Fi and supporting BLE provisioning.
Key Requirements
- USB-C receptacle, 5 V sink/default supply.
- Design must tolerate common 0.5 A to 3 A USB-C sources, but normal product current is limited for default-current compatibility.
- Include reverse-current/OVP/UVLO/OCP/inrush protection.
- Wireless: 2.4 GHz 802.11 b/g/n and BLE 5.x.
- Digital temperature/RH sensor.
- Low-power firmware strategy despite USB power.
- Consumer product regulatory planning.
Architecture Decisions
Table
| Block | Decision | Rationale |
|---|---|---|
| MCU/radio | ESP32-C3-WROOM-02-N4 | Lower power/cost than ESP32-S3, integrated antenna, Wi-Fi b/g/n + BLE 5.x, native USB Serial/JTAG. |
| Sensor | Sensirion SHT41-AD1B-R3 | Accurate I2C temperature/RH sensor with low-power operation. |
| USB-C | Sink-only Rd pulldowns on CC1/CC2 | Simple 5 V USB-C input without PD complexity. |
| Input protection | TPS259530 eFuse | Programmable current limit, UVLO, inrush control, reverse-current/OVP-class protection. |
| 3.3 V supply | MP28301 low-IQ buck | Better thermal/efficiency margin than LDO for Wi-Fi bursts. |
Electrical Interfaces
- USB D−: ESP32-C3 IO18 via USBLC6 ESD array.
- USB D+: ESP32-C3 IO19 via USBLC6 ESD array.
- I2C SDA: ESP32-C3 IO4 with 4.7 kΩ pull-up.
- I2C SCL: ESP32-C3 IO5 with 4.7 kΩ pull-up.
- Status LED: ESP32-C3 IO7 through 1 kΩ.
- BOOT: GPIO9 with 10 kΩ pull-up and button to GND.
- GPIO8: 10 kΩ pull-up for joint USB/UART download mode.
- GPIO2: 10 kΩ pull-up for ESP32-C3 boot recommendation.
- EN: 10 kΩ pull-up, 1 µF RC delay, reset button to GND.
Layout Requirements
- Place ESP32 module antenna at board edge with manufacturer antenna keepout; no copper under antenna on any layer.
- Place SHT41 away from MCU, buck regulator, USB connector metal, LEDs, and other heat sources; add enclosure ventilation.
- Place USB ESD array close to connector.
- Keep buck VIN/SW/inductor/output-cap loop compact with solid ground return.
- Put eFuse support parts close to U3 pins.
Open Items
- PCB placement/routing not yet performed.
- Final current limit, thermal behavior, and RF performance must be validated on prototype.
- Regulatory documentation must be completed with final layout, test reports, and module grant/labeling evidence.
Purpose
Key Requirements
Architecture Decisions
Electrical Interfaces
Layout Requirements
Open Items
