BME33M251A is designed for both the micro:bit and Arduino (BMduino) ecosystems. Depending on the development platform, users can pair it with the micro:bit IoT Expansion Board BMB81TM01A or the BMduino IoT Expansion Board BMB81TB01A to simplify wiring and speed up system integration, resulting in faster and more efficient development.

The BM25S2021-1 on board is a fully digital resistive humidity and temperature sensor that integrates temperature sensing, humidity sensing, an analog front-end, and an A/D converter. All modules are factory-calibrated, with calibration data stored internally. Users can directly obtain accurate temperature and humidity readings without additional software calibration.

The module communicates with the host MCU through the BMCOM interface and supports both I²C and One-wire modes. When the SCL/CS pin is connected to GND, the module enters One-wire mode; otherwise, it operates in I²C mode. The I²C address is fixed at 0x5C and supports bus speeds up to 400kHz, making it easy to integrate into various microcontroller platforms.

In real-world applications, BME33M251A can serve as the core sensor for environmental monitoring products—for example: smart fans that adjust airflow based on humidity, dehumidifiers that operate according to indoor humidity levels, air-conditioner energy-saving systems, or IoT nodes that monitor long-term environmental data via cloud platforms.

The module operates with a wide supply voltage range (2.7V–5.5V), making it compatible with both 3.3V and 5V systems. With the official Arduino Library and example code, developers can quickly retrieve, convert, and display temperature and humidity data, significantly shortening development time from prototype to final validation.

1. Operating voltage: 2.7V ~ 5.5V
2. Operating current: < 2.5mA @ 5V
3. Standby current: < 3μA @ 5V
4. Integrated digital temperature & humidity sensor: BM25S2021-1
5. Humidity specifications
   - Range: 10%RH ~ 95%RH
   - Resolution: 0.1%RH
   - Accuracy: ±3%RH (typ.)
6. Temperature specifications
   - Range: -40℃ ~ 80℃
   - Resolution: 0.1℃
   - Accuracy: ±0.5℃ (Ta = -40℃~60℃ typ.)
7. Factory-calibrated; calibration data stored internally—no user calibration required
8. Communication Interface
   - BMCOM × 1 (NC, SCL/CS, SDA, VDD, GND)
   - Supports I²C / One-wire
   - I²C address: 0x5C; bus speed ≤ 400kHz
   - Logic level reference: 2.7V ~ 5.5V
9. Supports MCU internal pull-ups for simplified circuit design
10. Arduino Library support with example code
11. Module size: 40mm × 24mm × 8mm

BME33M251A connects to the host controller through the BMCOM interface and can operate in either I²C or One-wire mode. Simply connect the power, ground, and data pins according to the pin definitions to Arduino UNO, BMduino UNO, or other compatible development boards—no additional circuit components required.

Q1: How do I switch between I²C and One-wire modes?

A: Connect the SCL/CS pin to GND to enable One-wire mode. Leave it unconnected for I²C mode.

Q2: How often can temperature and humidity data be read?

A: A minimum interval of 300ms is recommended between readings. For continuous sampling, a 2-second interval is advised for stable results.

Q3: Does the module require additional calibration?

A: No. The module is factory-calibrated and stores calibration data internally.

Q4: Do I need external pull-up resistors for the I²C bus?

A: Most development boards (e.g., Arduino, BMduino) already include pull-ups, so external resistors are typically unnecessary. For custom hardware, add pull-ups based on your bus characteristics.