ST launches industry's first sensor with built-in pedometer function

With the gradual improvement of digital life, smart wearable devices have been favored by many manufacturers. The upstream and downstream of the industry chain continue to promote the upgrading of the industry in their own ways. First, Baidu launched an open source bracelet, and then Tencent launched " WeChat Sports " . Many manufacturers continue to improve the product experience of smart wearable devices. STMicroelectronics, as a leading manufacturer of motion sensors, has also launched its own killer products, including the LIS2DS12TR (independent accelerometer) and LSM6DS3/33TR (accelerometer and gyroscope integrated inertial module unit) motion sensors with built-in pedometer function.

Research reports show that the global sales of wearable devices reached 24 million units in 2014 , and are expected to reach nearly $ 27 billion by 2020. Many giant companies and emerging startups are scrambling to seize the high ground of wearable devices. STMicroelectronics' motion sensors will help customers accelerate product development cycles, solve the basic functional requirements of wearable devices from the perspective of sensor hardware, and save customers more time for product innovation.

Motion sensor pedometer principle

The figure above shows the raw data waveform collected by the motion sensor. The horizontal axis is the time value and the vertical axis is the intensity value .

The first shorter waveform is produced when walking, and its characteristics are low cadence and low intensity. The following waveform is produced when running, and its cadence is faster than walking, and its intensity is correspondingly increased. Each peak represents a step.

Data features:

Running cadence > walking cadence

Running intensity > walking intensity

The intensity detected by frequency and acceleration can easily distinguish between running and walking .

From the above, we can know that the key elements of designing a pedometer are: acceleration threshold, frequency (interval time), and starting step count (to avoid misjudgment). LIS2DS12TR and LSM6DS3TR provide full open design in these key elements.

The following figure shows the basic principle of the motion sensor's step counting. The blue line represents the actual vibration intensity, the green line represents the minimum threshold value, and the vibration exceeding the threshold value is judged as running. The red dot represents the detected running action.

Knowing the above, how does the ST sensor department help customers save money on pedometer algorithms? We designed the pedometer sensor based on the following two points

1. Based on many years of experience in step counting development, a set of default parameters with an accuracy of up to 95% is provided

2. Customers can further optimize the above parameters according to the actual product, which can be achieved by simply changing the register

Sharing of some test data

Compared with existing sensors with built-in MCU and pedometer function, LIS2DS12TR uses ASIC to implement pedometer, which is more power-saving than embedding MCU and provides a smaller product package (2mmx2mm).

Advantages of STMicroelectronics' motion sensor with built-in pedometer function

• Direct output of pedometer steps

• The pedometer can accumulate more than 60,000 steps per day

• Can work 24 hours a day without application processor

• 10uA ultra low current

• The algorithm can be adjusted through registers

• No need to take up more PCB space

• No significant cost increase for new features

• Interrupts and timestamps

Free samples of LIS2DS12TR and LSM6DS3TR are currently available from multiple channels.

1. STMicroelectronics Authorized Distributor

2. Online QQ group application: 415506792

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