• 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.

• 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.

• 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.

• 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.

Diagram

• 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.

• 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.

• 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.

• To be maintained in power-budget project file.
• Preliminary sizing target: support ESP32 WiFi current peaks plus sensor and LED loads with margin.

• 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 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.

• 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.

• 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.

• 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.

• Initial requirements captured from user request.