USB-C WiFi BLE Sensor Design
Worked for 12 mins 8 sec
I started the USB-C WiFi/BLE temperature-humidity sensor node and made concrete project progress before tool execution stopped.
Completed:
- Renamed the project to USB-C WiFi BLE T-RH Sensor Node and updated the description.
- Created a project specification file capturing the architecture, assumptions, USB-C 5 V input, WiFi/BLE, digital T/RH sensing, protection, and layout expectations.
- Created a power-budget file. The design is sized around a ~560 mA 3.3 V peak load, so I selected a buck-regulator direction instead of a thermally marginal small LDO.
- Selected and added main schematic parts:
- ESP32-S3-WROOM-1 WiFi/BLE module
- SHT40-AD1B-R2 I2C temperature/humidity sensor
- USB-C receptacle
- TPS25210L eFuse/protection IC
- MP28301 3.3 V buck regulator
- USBLC6-2SC6 USB data ESD protection
- Boot/reset switches, status LED, inductor, and required passives
- Consulted datasheets for the ESP32-S3 module, SHT40 sensor, TPS25210 protection IC, USBLC6 ESD array, and USB-C connector.
Remaining work:
- Finish datasheet extraction for the MP28301 buck regulator.
- Wire the schematic: USB-C CC/VBUS/data, eFuse protection, 3.3 V buck, ESP32 USB/I2C/boot/reset, SHT40, LED, and all decoupling.
- Add or adjust any buck feedback/support parts required by the MP28301 datasheet.
- Run schematic review/ERC and fix all violations.
- Create firmware starter and board bring-up project files.
- Only after the schematic is clean, move to layout with user confirmation.
Finish buck design
Wire full schematic
Run ERC check
Add bring-up notes
Optimize module choice
Refine this doc
Ask about this doc
Project Specification — USB-C WiFi BLE T-RH Sensor Node
Project Overview
- Status: Draft schematic in progress
- Device: Consumer environmental sensor node measuring temperature and relative humidity.
- Connectivity: 2.4 GHz WiFi 802.11 b/g/n plus Bluetooth LE 5.x.
- Power: USB-C 5 V sink input with protected power path and 3.3 V system rail.
Intended Use
- Indoor consumer environmental monitoring node powered from a USB-C wall adapter, hub, or host port.
- Prototype-to-production intent using SMD components and module-based RF to reduce RF design risk.
What the Device Should Do
- Accept default USB-C 5 V input.
- Protect downstream electronics from reverse current, over-voltage, under-voltage, and over-current events.
- Power a low-power WiFi/BLE MCU and digital T/RH sensor from a regulated 3.3 V rail.
- Provide USB data/programming path where supported by the MCU module.
- Measure and report temperature/humidity over WiFi and BLE.
Main Features
- USB-C receptacle configured as sink with independent CC pull-downs.
- 5 V input protection for ESD/surge, OVP/UVLO/OCP, and reverse blocking.
- 3.3 V regulator sized for WiFi transmit peaks.
- ESP32-class low-power WiFi/BLE module with integrated antenna.
- Digital I2C temperature/humidity sensor.
- Boot/reset buttons and status LED.
System Architecture
Diagram
Hardware Subsystems
- Power input: USB-C sink, 5 V default, planned for 0.5 A to 3 A sources without USB-PD negotiation.
- Protection: Dedicated protected load-switch/eFuse style input path plus TVS protection.
- Regulation: 5 V to 3.3 V regulator sized for WiFi/BLE peak current.
- Compute/radio: ESP32-S3/C3 class module to avoid custom RF matching and simplify certification path.
- Sensing: Digital I2C temperature/humidity sensor with local decoupling and shared bus pull-ups.
- User/debug: USB programming, boot/reset controls, status LED.
Interfaces and Connections
- USB-C VBUS, GND, CC1, CC2, D+, D-.
- 3.3 V power rail to MCU and sensor.
- I2C SDA/SCL between MCU and sensor.
- GPIO for status LED, BOOT, RESET/EN.
Power and Runtime Expectations
- USB powered only; no battery runtime target.
- Low-power firmware should use modem sleep/light sleep between measurements when possible.
- Hardware supports WiFi peak current; actual power depends primarily on radio duty cycle.
Power Tree and Power Budget
- To be maintained in
power-budgetproject file. - Preliminary sizing target: support ESP32 WiFi current peaks plus sensor and LED loads with margin.
Manufacturing and Assembly Expectations
- Consumer-use, SMD production-intent design.
- Use module-based RF and keep antenna at board edge during layout.
- Include test points for VBUS, protected 5 V, 3V3, GND, I2C, EN, BOOT.
Firmware-Relevant Hardware Requirements
- Firmware should initialize USB serial/debug, WiFi station mode, BLE advertising/service, I2C sensor polling, and status LED.
- Bootloader access via BOOT and RESET/EN controls.
Physical Design Expectations
- ESP32 module antenna must face outward at board edge with copper/component keepout per module datasheet.
- USB-C connector should be placed on board edge.
- T/RH sensor should be away from regulator heat, MCU heat, and copper heat-spreading areas.
Important Design Decisions
- Use an ESP32 module rather than bare RF IC for lower RF risk.
- Use USB-C default-current sink behavior, not USB-PD, unless requirements later demand >5 V or negotiated power.
- Use I2C digital T/RH sensor for low power and simple firmware.
Assumptions
- SMD assembly is acceptable for consumer-use production intent.
- USB-C input remains 5 V only; no USB Power Delivery negotiation required.
- Sensor is intended for indoor ambient air, not sealed or condensing environments.
Change Notes
- Initial requirements captured from user request.
Welcome 👋
Flux helps you build PCBs faster with an AI teammate!
Create your account to collaborate, stay updated, fork your own version, and get instant answers from our AI agent.