BMA46M422A is a module designed by Best Modules for both the micro:bit and Arduino (BMduino) ecosystems. Depending on your development platform and main controller, you can pair it with the micro:bit IoT Expansion Board BMB81TM01A or the BMduino IoT Expansion Board BMB81TB01A to make sensor/module wiring more intuitive and integration significantly faster, greatly improving development efficiency.

The module integrates Best Modules’ digital PIR sensing device BM22S4221-1, combining optics, the PIR sensor, and signal-processing circuits into a single compact module. Since factory calibration is already performed, developers can skip complicated analog tuning and focus directly on system logic and application design.

Through the BMCOM interface and UART communication (default baud rate: 9600bps), users can read detection status, adjust sensitivity, configure trigger duration, alarm output time, and even output polarity. An official Arduino Library is also available, making it easy to incorporate motion-detection features into Arduino or BMduino projects.

Designed for low-power applications, BMA46M422A typically operates under 1.2mA @ 3V and consumes less than 10μA in standby. With a built-in temperature sensor and compensation algorithm, the module maintains stable performance under various environmental temperature changes.

The warm-up time is approximately 30 seconds. During this period, the module performs internal calibration before entering normal detection mode. Once ready, it can be used in applications such as garage lighting, corridor illumination, office energy-saving systems, and proximity-activated smart devices.

1. Operating voltage: 3.0V ~ 5.5V
2. Operating current: <1.2mA @ 3V (low-power mode)
3. Standby current: <10μA @ 3V
4. Integrated PIR sensing module: BM22S4221-1
   - Detection angle: 122° / 106° (H / V)
5. Adjustable sensing parameters
   - Configurable sensitivity
   - Adjustable detection duration
   - Adjustable output hold time
   - Selectable alarm output polarity (High / Low)
6. Built-in temperature sensor with automatic temperature-compensation algorithm
7. Warm-up time: approx. 30 seconds (VDD = 3.3V)
8. Communication interface
   - BMCOM (STA, RX, TX, VDD, GND)
   - Communication protocol: UART
   - Baud rate: 9600bps
   - Logic level reference: 3.0V ~ 5.5V
9. Arduino Library support for rapid development
10. Module size: 48mm × 24mm × 26.2mm

BMA46M422A communicates with the main controller via the BMCOM interface. It can be connected to an Arduino UNO or Best Modules’ BMduino UNO through simple wiring. Once the BMCOM connector is linked to power, ground, UART pins, and the status output pin, the module can operate without any additional circuitry.

Q1: Why doesn’t the module respond immediately after powering on?

A: The module requires about 30 seconds of warm-up time. During this period, internal calibration is performed. Avoid sending commands during warm-up to prevent incorrect behavior. Once warm-up is complete, normal detection begins.

Q2: How can I tell if motion is currently detected?

A: You may check (1) the Alarm LED—lit when motion is detected (if output polarity is set to High), or (2) the STA output pin—Low when idle and High when motion is detected. You may also read detection results via UART.

Q3: Can the sensing distance or sensitivity be adjusted?

A: Yes. Through UART commands, you can adjust sensitivity, detection duration, output time, and more. Refer to the protocol document and sample code for configuration guidance.

Q4: Can this module be installed outdoors or in high-temperature environments?

A: The built-in temperature sensor and compensation algorithm help maintain stability, but outdoor exposure to direct sunlight, heat, or harsh weather is not recommended without proper protective enclosure. Avoid pointing the lens directly at strong light sources.

1. PIR sensing module BM22S4221-1 — includes protocol specifications and technical details available from Best Modules.
2. Official Arduino Library and example code for implementing motion detection, sensitivity adjustment, and alarm configuration.