Temperature and Humidity Sensor Node Design
Placed components
2:56
Placed 27 component(s): U1, C3, C6, C7, H3, H2, J1, R5, C5, R2, H4, U4, C2, R3, R1, C4, U3, R7, J2, H1, R9, U2, R6, R8, R4, C8, C1
0:03
Work done
- Built the schematic for the USB-C powered Wi‑Fi/BLE temperature/humidity node: ESP32‑S3 module, SHT31 sensor, USB‑C default-sink input, TPS25200 protection, AP2112 3.3V regulation, decoupling, I²C pull-ups, boot/reset, USB data, and UART debug access.
- Configured a compact 50 mm × 50 mm 4-layer PCB setup and placed all components with USB‑C at the edge, ESP32 antenna facing outward, sensor away from the power section, and mounting holes in the corners.
- Added documentation: Project Specification, Firmware Pin Map, and Design Review Results.
- ✅ Complete protected USB-C power-path schematic and 3.3V rail are present.
- ✅ Dual-radio MCU, digital T/RH sensor, support passives, and debug/programming connections are integrated.
- ⚠️ PCB placement is complete, but final routed PCB production readiness is not complete yet.
- ⚠️ Final checks found remaining PCB routing airwires and one copper-overlap item that must be resolved before fabrication.
Route the PCB traces, inspect the copper-overlap item, then rerun final checks before manufacturing export.
Route remaining airwires
Inspect copper overlap
Run final review
Check antenna placement
Export production files
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USB-C WiFi/BLE Temperature and Humidity Sensor Node Specification
Functional goals
Consumer-grade low-power environmental sensor node powered from USB-C 5 V default power. The node measures temperature and relative humidity with a digital I2C sensor and reports data using an ESP32-S3 Wi-Fi/BLE module supporting 2.4 GHz 802.11 b/g/n and BLE 5.x.
Architecture
- USB-C receptacle: USB4215-03-A, 5 V default sink with 5.1 kΩ Rd pull-downs on CC1/CC2.
- Input protection: TPS25200 eFuse stage for over-current limiting, over-voltage clamp/lockout, UVLO, and reverse-current blocking while disabled.
- Current planning: RILIM = 36 kΩ, 1%, selected from TPS25200 datasheet examples to keep current limit below 3 A while allowing high-current USB-C sources.
- 5 V protected rail: eFuse output named 5V_PROTECTED.
- 3.3 V rail: AP2112K-3.3TRG1 LDO powering ESP32-S3 module and SHT31 sensor.
- MCU/RF: ESP32-S3-WROOM-1-N16R8 with PCB antenna, USB D+/D- and UART0 debug access.
- Sensor: SHT31-DIS-B2.5KS on I2C with 4.7 kΩ pull-ups.
Pin mapping
- I2C SDA: ESP32-S3 IO8 to SHT31 SDA.
- I2C SCL: ESP32-S3 IO9 to SHT31 SCL.
- SHT31 ALERT: ESP32-S3 IO5.
- eFuse FAULT: ESP32-S3 IO4.
- USB D-: ESP32-S3 IO19.
- USB D+: ESP32-S3 IO20.
- UART0 TX/RX: debug header J2 pins 3/4.
- EN reset: J2 pin 5 with 10 kΩ pull-up and 1 µF capacitor.
- BOOT IO0: J2 pin 6 with 10 kΩ pull-up.
PCB/layout requirements
- Consumer IoT size target: 50 mm × 50 mm unless enclosure requires otherwise.
- Stackup: 4 layers for RF/USB EMI robustness, continuous ground reference below top-layer signals, and internal power distribution.
- ESP32-S3 PCB antenna must be placed at a board edge with approximately 5 mm antenna overhang/keepout and no copper/components in the antenna keepout zone.
- USB-C connector must be placed on a board edge.
- Power protection and regulator must be grouped near USB-C input.
- SHT31 must be kept away from regulator/eFuse heat and placed near board edge or ventilation region for accurate environmental sensing.
Production notes
- Replace generic passives with preferred production MPNs before assembly release if required by the manufacturer.
- Run ERC/DRC and review antenna keepout before manufacturing export.
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