USB-C WiFi BLE Sensor Design

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Completed so far:
  • Renamed the project to USB-C WiFi BLE Sensor Node.
  • Updated the project description.
  • Created the initial Project Specification file.
  • Confirmed the schematic started empty.
  • Sourced and added the main components:
    • ESP32-S3-MINI-1-N8 Wi‑Fi/BLE module
    • SHT40 temperature/humidity sensor
    • USB-C receptacle
    • USB input protection/current-limit IC
    • USB-C port protection IC
    • 3.3 V buck regulator
    • USB D+/D− ESD protection
    • BOOT and RESET buttons
    • Status LED
    • 5 V, 3.3 V, and GND test points
Still remaining:
  • Add support passives: decoupling capacitors, I2C pull-ups, USB-C CC pull-downs, regulator feedback/boot/input/output components, LED resistor, boot/reset RC parts.
  • Query datasheets for every active IC before wiring.
  • Wire the USB-C input, protected 5 V path, 3.3 V regulator, ESP32, SHT40, USB data, buttons, LED, and test points.
  • Run schematic checks and fix ERC issues.
  • Create firmware, board bring-up, and regulatory documentation.
  • After schematic validation, ask for approval before moving to PCB layout.
Wire USB-C power
Check datasheets
Add support passives
Run ERC/DRC
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Files

Schematic

Layout

Preview

U2
D1
TP1
TP2
TP3
U4
SW1
SW2
LED1
U3
J1
U5
U1
Project Specification
Project Overview
Status: Draft. USB-C powered consumer temperature/humidity sensor node with Wi-Fi 2.4 GHz 802.11 b/g/n and BLE 5.x connectivity.
Intended Use
Indoor consumer environmental monitoring node powered from USB-C 5 V adapters/ports. Intended for prototype-to-production schematic baseline.
What the Device Should Do
  • Measure ambient temperature and relative humidity using a digital sensor.
  • Connect over Wi-Fi and BLE for setup/telemetry.
  • Accept USB-C default 5 V input from sources advertising roughly 0.5 A to 3 A.
  • Protect downstream electronics from reverse current/backfeed, over-voltage, under-voltage, and over-current faults.
Main Features
  • ESP32-class ultra-low-power Wi-Fi/BLE module with integrated antenna.
  • I2C digital T/RH sensor.
  • USB-C sink-only 5 V input with CC pull-downs.
  • 3.3 V regulated rail.
  • Boot/reset controls, status LED, programming over native USB where supported.
System Architecture
Diagram



  
    
  
  
    
  
















USB-C node_5V Input
Input Protection OVP UVLO OCP Reverse Blocking
3.3V Regulator
Wi-Fi BLE MCU Module
Digital Temp RH Sensor
USB D Plus D Minus ESD
I2C Bus
Hardware Subsystems
  • Power: USB-C 5 V sink, protected 5 V rail, low-noise 3.3 V regulator sized for Wi-Fi peaks.
  • Compute/Radio: ESP32-family module for Wi-Fi b/g/n and BLE 5.x; module antenna requires PCB keepout.
  • Sensor: digital I2C temperature/relative humidity sensor.
  • Protection: VBUS ESD/surge, OVP/UVLO/OCP/reverse blocking power-path protection, USB data ESD.
  • Debug/UI: native USB programming, BOOT and RESET buttons, status LED, test points.
Interfaces and Connections
  • USB-C receptacle: VBUS, GND, CC1/CC2 Rd, D+/D-.
  • I2C: SDA/SCL with one pull-up pair to 3.3 V.
  • User controls: BOOT, RESET.
  • Test points: 5 V protected, 3.3 V, GND, I2C lines.
Power and Runtime Expectations
USB-C powered only; low-power firmware should use modem sleep/light sleep between measurements. No battery runtime target.
Power Tree and Power Budget
Preliminary worst-case sizing target: 3.3 V rail approximately 350 mA peak for Wi-Fi/BLE bursts plus sensor/LED margin. USB input protection and regulator should be rated above this with margin; USB-C source-current advertisement must be respected in firmware/hardware if loads are expanded beyond this node.
Manufacturing and Assembly Expectations
Consumer-use prototype with SMD assembly, 2-layer or 4-layer PCB acceptable. RF antenna keepout required.
Firmware-Relevant Hardware Requirements
  • Initialize I2C T/RH sensor.
  • Support Wi-Fi and BLE provisioning/telemetry.
  • Native USB serial/JTAG programming if ESP32-C3/S3-class module is selected.
  • Control status LED and handle boot/reset straps correctly.
Physical Design Expectations
Place MCU module at board edge with antenna facing outward and copper keepout under antenna. USB-C at board edge. Sensor exposed to ambient airflow and thermally isolated from regulator/MCU heat.
Important Design Decisions
  • Use an ESP32 module rather than bare RF chip to reduce RF risk.
  • Use I2C digital humidity/temperature sensor.
  • Use USB-C sink-only default 5 V input; no USB-PD negotiation planned.
Assumptions
  • Consumer indoor ambient sensor; not safety-critical or medical.
  • USB-C is power plus native USB programming/debug, not USB host.
  • No display, battery, or external sensor cable unless later requested.
Change Notes
  • Initial specification created 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