USB-C WiFi BLE Sensor Design
Worked for 3 mins 22 sec
I started the USB-C Wi‑Fi/BLE temperature/humidity sensor node design and completed the early schematic setup work before execution stopped.
Completed:
- Renamed the project to USB-C WiFi BLE Environmental Sensor and updated the description.
- Created initial project files:
- Selected and added the main schematic parts:
- U1: ESP32-C3-MINI-1-N4 Wi‑Fi 802.11 b/g/n + BLE 5 module
- U2: SHT40-AD1F-R2 digital temperature/humidity sensor
- U3: TPS259474LRPWR eFuse for OVP/UVLO/OCP/reverse-current protection
- U4: AP63203WU-7 3.3 V / 2 A buck regulator
- J1: USB-C receptacle
- D1: TPD2EUSB30A USB D+/D− ESD protection
- Consulted datasheets for the ESP32-C3 module, SHT40 sensor, TPS25947 eFuse, AP63203 buck regulator, and USB ESD protector.
Key design decisions already grounded in datasheets:
- ESP32-C3 requires 3.0–3.6 V, with a supply sized for at least 0.5 A.
- ESP32-C3 USB native pins are IO18 = USB_D− and IO19 = USB_D+.
- ESP32-C3 EN must not float; datasheet recommends an RC delay, typically 10 kΩ + 1 µF.
- SHT40 runs from 1.08–3.6 V, uses I2C address 0x44, and needs 100 nF decoupling.
- AP63203 fixed 3.3 V buck recommended external parts:
- 10 µF input capacitor
- 3.9 µH inductor
- 2 × 22 µF output capacitors
- 100 nF bootstrap capacitor
- TPS259474 eFuse:
- IN range 2.7–23 V
- Adjustable UVLO/OVLO
- ILM resistor required; do not leave ILM floating
- ITIMER may be left open for fastest overcurrent response or populated with a capacitor for blanking
- PG is open-drain and needs pull-up if used
Remaining work:
- Add all support passives: USB-C CC pull-downs, buck inductor/caps, eFuse threshold/current-limit parts, ESP32 EN/reset/boot parts, I2C pull-ups, decoupling, LED, and test points.
- Wire the full schematic.
- Run ERC/review and fix all violations.
- Create firmware starter and board bring-up plan files.
- After schematic is clean, ask for approval before moving to PCB layout.
Finish schematic
Size eFuse resistors
Complete USB-C
Run ERC/DRC
Document decisions
Refine this doc
Ask about this doc
Project Specification
Project Overview
Status: Draft. USB-C powered consumer environmental sensor node with Wi-Fi + Bluetooth connectivity and a digital temperature/relative-humidity sensor.
Intended Use
Indoor consumer/prototype environmental monitoring powered from a USB-C 5 V source such as a wall adapter, hub, or computer port.
What the Device Should Do
- Measure ambient temperature and relative humidity digitally.
- Communicate over 2.4 GHz Wi-Fi 802.11 b/g/n and BLE 5.x.
- Power from USB-C 5 V default sink mode.
- Tolerate USB-C sources advertising approximately 0.5 A to 3 A, without drawing more than the design requires.
- Include input protection for reverse/over-voltage/under-voltage/over-current events.
Main Features
- ESP32-class ultra-low-power Wi-Fi/BLE MCU module with integrated antenna.
- Digital I2C T/RH sensor.
- USB-C receptacle for 5 V input and USB programming/debug.
- Protected 5 V power path, high-efficiency 3.3 V rail, boot/reset controls, status LED, and test points.
System Architecture
USB-C 5 V input -> CC sink configuration -> eFuse/protection -> 3.3 V regulator -> ESP32 Wi-Fi/BLE MCU + I2C T/RH sensor. USB D+/D- route to the MCU native USB interface through ESD protection.
Hardware Subsystems
- Power input/protection: USB-C receptacle, CC pull-downs, ESD, eFuse with OVP/UVLO/OCP/reverse-current protection.
- Regulation: 5 V to 3.3 V high-efficiency regulator sized for radio current peaks.
- Compute/radio: ESP32-C3/S3 class module with integrated 2.4 GHz antenna.
- Sensing: I2C digital temperature/humidity sensor with local decoupling.
- User/debug: boot and reset buttons, status LED, USB serial/JTAG programming.
Interfaces and Connections
- USB-C VBUS/GND/CC1/CC2 and USB 2.0 D+/D-.
- I2C SDA/SCL between MCU and T/RH sensor with one pull-up pair.
- GPIO for status LED and boot/reset controls.
Power and Runtime Expectations
USB-powered only in this revision. Low-power firmware should use radio sleep modes between readings, but USB supply means runtime is source-limited rather than battery-limited.
Power Tree and Power Budget
Preliminary sizing target: 3.3 V rail supports ESP32 radio peaks plus sensor and LED. Protection and regulator are selected after summing downstream load and checking thermal/current margins.
Manufacturing and Assembly Expectations
Consumer-use prototype with SMD assembly, integrated RF module to avoid custom RF matching, antenna at board edge with keepout during layout.
Firmware-Relevant Hardware Requirements
Native USB programming/debug, boot button, reset/enable circuit, I2C sensor initialization, Wi-Fi/BLE connectivity, low-power sleep policy, status LED.
Physical Design Expectations
Compact 2-layer or 4-layer PCB. ESP32 module antenna at board edge with no copper/components in antenna keepout. USB-C connector on board edge.
Important Design Decisions
- Use an RF-certified ESP32 module rather than bare RF silicon.
- Use a high-efficiency 3.3 V regulator instead of a small LDO because ESP32 Wi-Fi peaks make LDO thermal dissipation high from 5 V.
- Use independent USB-C CC pull-downs for sink-only 5 V operation.
Assumptions
- SMD assembly is acceptable.
- No battery is required in this revision.
- USB Power Delivery negotiation is not required; device is a default 5 V sink.
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.