BHI385 Smart IMU - Step Counter and Multi-Tap Detection

This page covers the BHI385's activity recognition sensors: the cumulative step counter and the multi-tap gesture detector.

Step counter

The step counter virtual sensor uses an adaptive pedometer algorithm in the firmware to count footsteps cumulatively. The count increments automatically as the sensor detects walking or running patterns; it resets to zero on power-off.

void setup()
{
    // ... begin() and loadFirmware() as above ...

    imu.enableStepCounter(100.0f);
}

void loop()
{
    if (imu.update())
    {
        if (imu.stepUpdated())
        {
            Serial.print("Steps: ");
            Serial.println(imu.getStepCount());
        }
        imu.clearUpdatedFlags();
    }
    delay(100);
}

Serial monitor Step Counter output

imu.enableStepCounter()

Enables the low-power step counter virtual sensor. The firmware increments the cumulative step count each time a footstep-like acceleration signature is detected. The count persists across enable/disable cycles but resets on power-off.

Returns value: true if the sensor was configured successfully

Function parameters:

Type	Name	Description
`float`	`rateHz`	Sensor update rate in Hz. Default: 100.0f

imu.getStepCount()

Returns the current cumulative step count as reported by the firmware step counter. Valid after update() returns with stepUpdated() true.

Returns value: Cumulative step count as uint32_t

Multi-tap detection

The multi-tap sensor detects sharp, brief acceleration impulses and classifies them as single, double, or triple taps. You configure which tap types to detect via a bitmask before enabling the sensor.

void setup()
{
    // ... begin() and loadFirmware() as above ...

    // Detect double taps only
    imu.enableMultiTapDetect(BHI385_TAP_DOUBLE, 100.0f);
}

void loop()
{
    if (imu.update())
    {
        if (imu.tapUpdated())
        {
            if (imu.getTapType() == BHI385_TAP_SINGLE)  Serial.println("Single tap!");
            if (imu.getTapType() == BHI385_TAP_DOUBLE)  Serial.println("Double tap!");
            if (imu.getTapType() == BHI385_TAP_TRIPLE)  Serial.println("Triple tap!");
        }
        imu.clearUpdatedFlags();
    }
}

imu.enableMultiTapDetect()

Enables the multi-tap detection virtual sensor. Writes the tap-type bitmask to the firmware parameter page before activating the sensor, so only the requested tap types generate events. Use BHI385_TAP_ALL to detect single, double, and triple taps simultaneously.

Returns value: true if the parameter write and sensor configuration both succeeded

Function parameters:

Type	Name	Description
`uint8_t`	`tapMask`	OR-combined bitmask of tap types to detect: BHI385_TAP_SINGLE (1), BHI385_TAP_DOUBLE (2), BHI385_TAP_TRIPLE (4), or BHI385_TAP_ALL (7). Default: BHI385_TAP_ALL
`float`	`rateHz`	Sensor update rate in Hz. Default: 100.0f

imu.getTapType()

Returns the tap type reported in the most recent multi-tap event. Matches one of the bhi385TapType enum values: BHI385_TAP_SINGLE, BHI385_TAP_DOUBLE, or BHI385_TAP_TRIPLE. Valid after update() returns with tapUpdated() true.

Returns value: Tap type as uint8_t (bhi385TapType enum value)

Step counter​