BLE Ambient Sensor Node

An indoor BLE sensor node powered via USB-C featuring temperature, humidity, and light sensors along with an OLED status display.

Executive Summary

This reference design defines the system architecture, critical component candidates, risk register, and validation path for BLE Sensor Node. It is a system-level design deliverable; verify critical claims with manufacturer evidence and prototype testing before production release.

Design Overview

Requirements Coverage

System Architecture

Power Topology: USB-C 5V VBUS -> Protection eFuse (TPS25940L) -> LDO Step-Down (MCP1700-3302) -> 3.3V System Rail powering BLE SoC, I2C Sensors, and OLED Display.

Module List

Power Tree and Signal Interfaces

Design Schemes

Off-the-Shelf BLE Module with I2C Peripherals ★

Utilizes a pre-certified BLE SoC stamp module mounted on a carrier baseboard, paired with standard I2C environmental sensors and an I2C OLED display, powered via a simple USB-C to 3.3V LDO regulator.

Trade-offs: Lowest prototyping risk and minimum layout complexity using shared I2C bus, optimized for rapid indoor node development.

Key IC selection

Main application processor and BLE radio

• Need: Execute sensor polling, OLED graphics rendering, and maintain stable BLE 5 LE connections with low idle power consumption.
• Class: RISC-V 32-bit single-core SoC with integrated 2.4GHz Wi-Fi and Bluetooth 5 LE in a certified module form factor.
• Shortlist: Espressif ESP32-C3 series, Nordic nRF52840 series
• Pick: Select fully integrated module variant (ESP32-C3-MINI-1-N4) with built-in PCB antenna and flash to eliminate RF matching overhead and pass modular certification easily.

Power path protection and 3.3V regulation

• Need: Safely accept 5V USB-C power, protect downstream electronics from over-voltage or transients, and step down to a clean 3.3V rail.
• Class: Active eFuse / Load Switch paired with a low-dropout (LDO) voltage regulator.
• Shortlist: TI TPS25940L + Microchip MCP1700, Analog Devices LTC4365 + TPS7A20
• Pick: Choose automotive/industrial-grade eFuse with adjustable overvoltage cutoff combined with an ultra-low quiescent current CMOS LDO to maximize efficiency at light loads.

Environmental and ambient light front-end

• Need: Accurately capture temperature, humidity, barometric pressure, and wide-dynamic-range ambient lux levels over a shared digital bus.
• Class: Integrated digital environmental sensor combo (Temp/Hum/Pressure) plus high-sensitivity digital ambient light sensor (ALS).
• Shortlist: Bosch BME280 + ams TSL25911FN, Sensirion SHT4x + Vishay VEML7700
• Pick: Select industry-standard I2C sensors with proven driver ecosystems and small footprint LGA/FN packages suitable for air-vented enclosure designs.

Risk register

Bring-up and Validation Plan

1. Power-off inspection and rail resistance checks
2. Current-limited first power-up; verify every rail before enabling loads
3. Validate interfaces and timing one subsystem at a time
4. Run thermal, fault-injection, EMC pre-scan, and endurance tests for the target environment

Key Components

5/5 modules matched to real parts. See the BOM tab for the full component table.

GCT USB4215-03-A + TI TPS25940L + Microchip MCP1700-3302 (MCP1700)

The candidate MPN 'MCP1700' matches the primary MPN prefix for MCP1700-3302 and is produced by Microchip.

Build Summary

• Difficulty: Intermediate
• Estimated time: 3-5 hours
• Tools required: Antistatic mat and wrist strap, Stereo microscope, Hot air rework station, Temperature-controlled soldering iron, Digital multimeter, PC with ESP-IDF environment

See the Build tab for the full step-by-step assembly guide.

Evidence and Limitations

• Confirm part parameters, certifications, and compatibility against current manufacturer documents.
• Treat industry compliance without test or certificate evidence as a compliance gap, not an approval.
• See Reference Images for visual artifacts and Build Guide for detailed assembly and bring-up steps.