TDK Advanced Pedometer and Event Detection (APEX)

Overview

This sample application shows how to use the APEX (Advanced Pedometer and Event Detection) features of TDK Invensense sensors. It consists of: ** Pedometer: Tracks step count, and provide details such as the cadence and the estimated activity type (Walk, Run, Unknown). ** Tilt Detection: Detects the Tilt when tilting the board with an angle of 30 degrees or more. The tilt event is generated when the position is held for 4 seconds. ** Wake on Motion (WoM): Detects motion per axis exceeding 195 mg threshold. ** Significant Motion Detector (SMD): Detects when the user has moved significantly. APEX features support are configured through devicetree.

References

https://invensense.tdk.com/download-pdf/an-000271-icm-42607x-and-icm-42670x-apex-motion-functions-description-and-usage/

Driver configuration

The APEX is based on accelerometer data only. The TDK Sensor driver configures accelerometer low power mode and the APEX operating frequency (25Hz or 50Hz).

Wiring

This sample uses an external breakout for the sensor. A devicetree overlay must be provided to identify the TDK sensor, the SPI or I2C bus interface and the interrupt sensor GPIO.

Building and Running

This sample supports TDK IMU devices. Each device needs to be aliased as tdk-apex-sensorN where N goes from 0 to 9. For example:

/ {
       aliases {
                       tdk-apex-sensor0 = &icm42670p;
               };
       };

This sample supports APEX feature of TDK device. It needs to be specified as bellow:

icm42670p: icm42670p@0 {
        apex = "pedometer";
}

Make sure the apex feature used is in devicetree, then build and run with:

# From the root of the zephyr repository
west build -b nrf52dk/nrf52832 samples/sensor/tdk_apex
west flash

Sample Output

icm42670p: icm42670p@0 {
        apex = "pedometer";
}

Found device "icm42670p@68", getting sensor data
[0:00:09.287]: STEP_DET     count: 6 steps  cadence: 2.0 steps/s  activity: Unknown
[0:00:09.689]: STEP_DET     count: 7 steps  cadence: 2.1 steps/s  activity: Walk
[0:00:10.051]: STEP_DET     count: 8 steps  cadence: 2.2 steps/s  activity: Walk
[0:00:10.433]: STEP_DET     count: 9 steps  cadence: 2.2 steps/s  activity: Walk
[0:00:10.835]: STEP_DET     count: 10 steps  cadence: 2.3 steps/s  activity: Walk

<repeats endlessly>

icm42670p: icm42670p@0 {
        apex = "tilt";
}

Found device "icm42670p@68", getting sensor data
[0:00:15.249]: TILT
[0:00:21.479]: TILT
[0:00:26.765]: TILT

<repeats endlessly>

icm42670p: icm42670p@0 {
        apex = "wom";
}

Found device "icm42670p@68", getting sensor data
[0:00:02.555]: WOM x=1 y=0 z=1
[0:00:02.636]: WOM x=0 y=0 z=1
[0:00:02.797]: WOM x=0 y=1 z=0
[0:00:02.877]: WOM x=0 y=0 z=1
[0:00:02.957]: WOM x=1 y=1 z=1

<repeats endlessly>

icm42670p: icm42670p@0 {
        apex = "smd";
}

Found device "icm42670@68", getting sensor data
[0:00:04.622]: SMD
[0:00:05.084]: SMD
[0:00:05.566]: SMD

<repeats endlessly>