Bosch BME280 & ams OSRAM TSL25911FN
BLE Ambient Sensor Node
Overview
An indoor BLE sensor node powered via USB-C featuring temperature, humidity, and light sensors along with an OLED status display.
KIM
System architecture
POWER
MODULE
SENSOR
DISPLAY
MISC
- USB_INTERFACE → POWER_USB_LDOPowerUnregulated 5V VBUS power feed and USB D+/D- data lines
- POWER_USB_LDO → BLE_SOC_MODULEPowerRegulated 3.3V system power rail for MCU
- POWER_USB_LDO → SENSORS_ENV_LIGHTPowerRegulated 3.3V system power rail for sensors
- POWER_USB_LDO → DISPLAY_OLED_I2CPowerRegulated 3.3V system power rail for OLED display
- BLE_SOC_MODULE → SENSORS_ENV_LIGHTI2CShared I2C bus for environmental and light sensors
- BLE_SOC_MODULE → DISPLAY_OLED_I2CI2CShared I2C bus for OLED status display
- USB_INTERFACE → BLE_SOC_MODULEUSBUSB D+/D- data connection for native USB programming and logging
Bill of materials
| Part number | Type | Component | Manufacturer | Package | Qty | Datasheet | Match |
|---|---|---|---|---|---|---|---|
| MCP1700 | POWER | GCT USB4215-03-A + TI TPS25940L + Microchip MCP1700-3302 Provides regulated 3.3V system power from USB-C 5V VBUS with over-voltage and reverse-current protection. | Microchip | — | 1 | Matched | |
| ESP32-C3-MINI-1-N4 | MODULE | Espressif ESP32-C3-MINI-1-N4 Main application processor and Bluetooth 5 LE radio for bi-directional data streaming and peripheral control. | Espressif Systems | 53-SMD Module | 1 | Matched | |
| TSL25911FN | SENSOR | Bosch BME280 & ams OSRAM TSL25911FN Monitors indoor temperature, relative humidity, barometric pressure, and ambient light level. | ams OSRAM | 6-WFDFN | 1 | Matched | |
| SSD1306-330MT | DISPLAY | 0.96-inch OLED Module (SSD1306 driver) Displays real-time sensor measurements and BLE connection status. | LanTu Micro(蓝图微电) | SMD,18.54x15.24mm | 1 | Matched | |
4 alternatives consideredAI verified | |||||||
| RC0603FR-075K1L | MISC | USB-C Port with CC Resistors Provides physical USB connection for power input, firmware flashing, and serial debugging. | Yageo | 0603 (1608 Metric) | 1 | Matched | |
1 alternatives consideredAI verified | |||||||
Build guide
3-5 hoursIntermediate
1
Procurement & Preparation
- Source and verify all required components including GCT USB4215-03-A USB-C connector, TI TPS25940L eFuse, Microchip MCP1700-3302 LDO, Espressif ESP32-C3-MINI-1-N4 module, Bosch BME280 sensor, ams OSRAM TSL25911FN light sensor, and SSD1306 0.96-inch OLED display.
- Prepare the PCB stencil, lead-free SMT solder paste (SAC305), and organize the workbench with a temperature-controlled hot air rework station and soldering iron.
2
Hardware Assembly & Wiring
- Apply solder paste to the PCB pads using the stencil, then place the GCT USB4215-03-A USB-C connector, TI TPS25940L protection IC, and Microchip MCP1700 LDO onto the power management section.
- Place the Espressif ESP32-C3-MINI-1-N4 module, Bosch BME280 sensor, and ams OSRAM TSL25911FN light sensor onto their respective SMT pads on the main board.
- Run the PCB through the reflow oven following the SAC305 temperature profile. Inspect all joints for bridging or cold solder connections under magnification.
- Manually solder the 0.96-inch OLED module (SSD1306 driver) to the designated I2C expansion header pins (3V3, GND, SDA, SCL) on the assembled PCB.
3
Firmware Setup
- Connect the BLE Sensor Node to a development PC via a USB-C cable. Access the native USB pins (D+, D-) routed to the ESP32-C3-MINI-1-N4 for programming and serial monitoring.
- Compile and flash the firmware using ESP-IDF or Arduino IDE, integrating the BME280 I2C driver, TSL2591 light sensor library, SSD1306 OLED display routines, and the ESP32-C3 BLE stack.
4
Testing & Calibration
- Perform a power-on self-test (POST) by connecting the USB-C power source. Measure the 3.3V power rail output from the MCP1700 LDO using a digital multimeter to ensure clean power delivery.
- Verify sensor data acquisition and OLED functionality. Confirm that temperature, humidity, pressure, and ambient light readings update dynamically on the 0.96-inch OLED display.
- Test bi-directional BLE 5 LE connectivity using a smartphone utility or central scanner app to verify data streaming, advertising packets, and remote sensor polling.
Document
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
| Requirement | Architecture coverage | Status |
|---|---|---|
| Indoor environmental monitoring (temperature, humidity, light) | Pending validation | Needs verification |
| Bi-directional BLE data streaming with mobile apps and gateways | Pending validation | Needs verification |
| OLED status display for real-time sensor data and connection status | Pending validation | Needs verification |
| USB-C powered operation | Pending validation | Needs verification |
| Item | Details |
|---|---|
| Product Type | BLE Sensor Node |
| Key Functions | Indoor environmental monitoring (temperature, humidity, light), Bi-directional BLE data streaming with mobile apps and gateways, OLED status display for real-time sensor data and connection status, USB-C powered operation |
| Power Source | USB-C 5V |
| Connectivity | Bluetooth |
| Size | approx. 80mm x 50mm |
| Environment | indoor |
| Difficulty | Intermediate |
| Est. Time | 3-5 hours |
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
| Module ID | Type | Name | Function | Voltage |
|---|---|---|---|---|
| POWER_USB_LDO | POWER | GCT USB4215-03-A + TI TPS25940L + Microchip MCP1700-3302 | Provides regulated 3.3V system power from USB-C 5V VBUS with over-voltage and reverse-current protection. | 5V to 3.3V |
| BLE_SOC_MODULE | MODULE | Espressif ESP32-C3-MINI-1-N4 | Main application processor and Bluetooth 5 LE radio for bi-directional data streaming and peripheral control. | 3.3V |
| SENSORS_ENV_LIGHT | SENSOR | Bosch BME280 & ams OSRAM TSL25911FN | Monitors indoor temperature, relative humidity, barometric pressure, and ambient light level. | 3.3V |
| DISPLAY_OLED_I2C | DISPLAY | 0.96-inch OLED Module (SSD1306 driver) | Displays real-time sensor measurements and BLE connection status. | 3.3V |
| USB_INTERFACE | MISC | USB-C Port with CC Resistors | Provides physical USB connection for power input, firmware flashing, and serial debugging. | 5V |
Power Tree and Signal Interfaces
| From | To | Type | Interface / rail | Voltage |
|---|---|---|---|---|
| USB_INTERFACE | POWER_USB_LDO | power | Power | 5V |
| POWER_USB_LDO | BLE_SOC_MODULE | power | Power | 3.3V |
| POWER_USB_LDO | SENSORS_ENV_LIGHT | power | Power | 3.3V |
| POWER_USB_LDO | DISPLAY_OLED_I2C | power | Power | 3.3V |
| BLE_SOC_MODULE | SENSORS_ENV_LIGHT | data | I2C | 3.3V |
| BLE_SOC_MODULE | DISPLAY_OLED_I2C | data | I2C | 3.3V |
| USB_INTERFACE | BLE_SOC_MODULE | data | USB | 3.3V |
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
| ID | Area | Severity | Detail | Mitigation |
|---|---|---|---|---|
| r1 | thermal | med | Self-heating from the ESP32-C3 module and local LDO inside a compact, enclosed indoor sensor node can bias the BME280 temperature and relative humidity readings upward. | Place the BME280 as far as thermally practical from the power management IC and SoC, utilize thermal reliefs on copper planes, and apply a firmware temperature compensation offset based on power state. |
| r2 | emi | med | High-frequency I2C clock and data toggling for refreshing the SSD1306 OLED display can couple noise into the adjacent BME280 and TSL2591 lines or desense the ESP32-C3 2.4GHz antenna. | Route I2C traces away from the module's PCB antenna clearance zone, add series damping resistors (22-33 ohms) on the I2C lines if trace lengths are long, and ensure solid ground plane continuity underneath. |
| r3 | supply | high | Global semiconductor shortages frequently impact specific environmental sensor variants like the Bosch BME280 and ams TSL25911FN, risking line stoppage. | Design fallback land patterns or software abstraction layers to support alternate pin-compatible or drop-in pin-out equivalent sensors (e.g., Sensirion or Lite-On alternatives) during layout. |
Bring-up and Validation Plan
- Power-off inspection and rail resistance checks
- Current-limited first power-up; verify every rail before enabling loads
- Validate interfaces and timing one subsystem at a time
- 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.