USB-C Temperature Humidity Sensor Node
Worked for 6 mins 35 sec
I renamed the project to USB-C WiFi BLE Environmental Node and updated the description. I also created a project specification file capturing the requirements, architecture, assumptions, and initial power budget: Project Specification.
I selected and researched likely core parts:
- MCU/radio: ESP32-C3-WROOM-02-N4 — Wi‑Fi 2.4 GHz 802.11 b/g/n + BLE 5, integrated PCB antenna, native USB pins.
- Sensor: SHT40-AD1B-R2 — low-power I2C temperature/RH sensor.
- USB-C connector: USB4105-GF-A / USB-C 2.0 receptacle.
- Input protection candidate: MP5036AGJ-P eFuse/load switch, but its datasheet text was not accessible in this run, so wiring was not started.
- Regulator: AP2114H-3.3TRG1 3.3 V / 1 A LDO; datasheet confirmed 4.7 µF input/output capacitors, EN behavior, 1 A rating, and thermal limits.
- USB data ESD: USBLC6-2SC6.
- VBUS ESD: TPD1E05U06DPYR.
- Reset/boot buttons and status LED candidates were found.
Initial power sizing:
- ESP32-C3 rail should be designed for at least 500 mA peak.
- SHT40 is sub-mA during measurement, unless heater is used.
- 3.3 V rail target is about 510 mA peak minimum, so the 1 A AP2114 LDO has current margin, but layout copper/thermal handling will matter.
No schematic components were added or wired yet because execution credits ran out before the build step. Remaining work is to add components, wire the USB-C protection/regulator/ESP32/SHT40/support passives, create firmware notes, run schematic review, and fix any violations.
Add core parts
Find eFuse
USB-C input schematic
Run ERC
Document assumptions
Refine this doc
Ask about this doc
Project Specification
Project Overview
Status: Draft.
USB-C powered consumer environmental sensor node measuring temperature and relative humidity, with 2.4 GHz Wi-Fi 802.11 b/g/n and BLE 5.x connectivity.
Intended Use
Indoor consumer/IoT environmental monitoring node powered from USB-C 5 V adapters, hubs, or ports. Intended as a compact prototype/production-intent reference design.
What the Device Should Do
- Accept 5 V from USB-C in default sink mode.
- Measure temperature and relative humidity using a digital sensor.
- Communicate over Wi-Fi and Bluetooth Low Energy.
- Support low-power firmware modes when not actively transmitting.
- Survive common USB input faults using reverse/OVP/UVLO/OCP protection.
Main Features
- USB-C receptacle, 5 V default sink, planned for 0.5–3 A advertised sources.
- Protected 5 V input path.
- 3.3 V rail for MCU and sensor.
- Wi-Fi + BLE MCU module.
- I2C temperature/RH sensor.
- Boot/reset controls and programming/debug access through native USB where supported.
System Architecture
Diagram
Hardware Subsystems
- Power input: USB-C sink with CC pull-downs.
- Protection: current limiting/fuse, surge/ESD protection, reverse-current blocking, OVP/UVLO load-switch/eFuse behavior.
- Regulation: 5 V to 3.3 V rail sized for Wi-Fi transmit peaks.
- Compute/radio: integrated MCU module with Wi-Fi 802.11 b/g/n and BLE 5.x.
- Sensing: digital I2C temperature/humidity sensor.
- User/debug: boot/reset buttons, USB programming, status LED.
Interfaces and Connections
- USB-C VBUS/GND/CC1/CC2/D+/D-.
- 3.3 V rail.
- I2C SDA/SCL between MCU and sensor.
- EN/reset and boot straps.
Power and Runtime Expectations
USB powered only. Firmware should use modem sleep/light sleep between measurements where practical. No battery runtime target in this revision.
Power Tree and Power Budget
Initial estimate:
- ESP32-class Wi-Fi/BLE module: about 240 mA active Wi-Fi typical, design for 500 mA short peaks.
- Digital T/RH sensor: <1 mA active, microamp sleep.
- Status LED/debug overhead: up to 5 mA.
- 3.3 V rail design target: 510 mA peak minimum; select regulator/protection with margin.
- USB-C input path should tolerate 0.5–3 A source capability, but firmware/hardware should not assume 3 A without Type-C current detection or fixed product limits.
Manufacturing and Assembly Expectations
Consumer-use prototype with SMD components. Use module-based RF design to avoid custom RF matching and certification complexity.
Firmware-Relevant Hardware Requirements
- I2C sensor polling.
- Wi-Fi + BLE stack support.
- USB serial/programming if using native USB MCU/module.
- Boot and reset controls.
- Low-power sleep strategy.
Physical Design Expectations
Place radio module antenna at board edge with antenna keepout. Keep input protection near USB-C. Place decoupling capacitors close to IC power pins.
Important Design Decisions
- Use an ESP32-C6/S3-class module rather than bare chip for integrated certified RF path.
- Use a high-efficiency 3.3 V regulator or thermally adequate LDO after checking current/thermal budget.
- Use an I2C digital humidity/temperature sensor such as SHT4x-class for low-power consumer sensing.
Assumptions
- USB-C Power Delivery negotiation is not required; device operates from 5 V only.
- Consumer indoor temperature range unless later specified.
- No battery charging in this revision.
Change Notes
- Initial specification created from user requirements.
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