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.
Project Overview
Intended Use
What the Device Should Do
Main Features
System Architecture
Hardware Subsystems
Interfaces and Connections
Power and Runtime Expectations
Power Tree and Power Budget
Manufacturing and Assembly Expectations
Firmware-Relevant Hardware Requirements
Physical Design Expectations
Important Design Decisions
Assumptions
Change Notes
