Measure types

carp_movesense_package has six measure types in the dk.cachet.carp.movesense namespace, which CARP Mobile Sensing (CAMS) collects from a Movesense sensor. Add each one to a protocol as Measure(type: MovesenseSamplingPackage.<constant>), in a task that runs on a MovesenseDevice:

The event-based measures stream while the sensor is connected, so start them with an ImmediateTrigger. The one-time measure collects once per run, so give it a trigger that repeats. See Event-based and one-time measures.

The data type of each measurement equals its measure type. For the measurement envelope around the data, see Measurements and data.

Sampling and timestamps

The measures have no sampling configuration. The package uses fixed rates of 125 Hz for ECG and 13 Hz for the inertial measurement unit (IMU). The sensor decides when it reports heart rate, taps and temperature.

Each event-based probe skips the first 10 notifications after it subscribes, to let the sensor stabilize. A task that starts again, for example from a trigger, skips them again.

sensorStartTime is the phone's time when the measurement was created, in microseconds since the epoch. The timestamp fields in the data hold the sensor's internal clock in milliseconds, which does not give the time of day. Use sensorStartTime to align Movesense data with other data.

Streaming heart rate, ECG and IMU data from one sensor at once may fail with status 408, because the sensor cannot keep up. Collect fewer streams at once, or record ECG in bursts, as in Taps.

Device information

DEVICE_INFO reads the sensor's /Info resource each time it runs, and collects nothing while the sensor is disconnected. To take a snapshot once a day, use a PeriodicTrigger:

protocol.addTaskControl(
  PeriodicTrigger(period: const Duration(days: 1)),
  BackgroundTask(
    measures: [Measure(type: MovesenseSamplingPackage.DEVICE_INFO)],
  ),
  movesense,
);

All fields of MovesenseDeviceInformation may be null, and the JSON leaves out the ones that are. The class has these fields:

{
  "__type": "dk.cachet.carp.movesense.deviceinformation",
  "manufacturerName": "Movesense Ltd",
  "productName": "Movesense",
  "variant": "Avocado",
  "design": "black",
  "hardwareCompatibilityId": "C",
  "serial": "233830000816",
  "pcbaSerial": "80413336500828200000100022666H4233",
  "softwareVersion": "2.1.5",
  "hardwareType": "H4",
  "apiLevel": "1",
  "address": "0C-8C-DC-1B-23-BF"
}

Taps

STATE reports single taps on the sensor. Movesense sensors deliver one kind of state change at a time, so the probe subscribes only to the tap state, System/States/4. The package authors tested this on the MD and HR2.

MovesenseStateChange has these fields:

MovesenseDeviceState also has the values moving, notMoving, connected, disconnected, doubleTap, acceleration and freeFall, which this measure does not produce. Because the probe skips the first 10 notifications, the first 10 taps after the measure starts are not recorded.

A SamplingEventTrigger can start another task on each tap. This protocol records 30 seconds of ECG every time the participant taps the sensor:

// Listen for taps while the sensor is connected
protocol.addTaskControl(
  ImmediateTrigger(),
  BackgroundTask(measures: [Measure(type: MovesenseSamplingPackage.STATE)]),
  movesense,
);

// Record 30 seconds of ECG after each tap
protocol.addTaskControl(
  SamplingEventTrigger(
    measureType: MovesenseSamplingPackage.STATE,
    triggerCondition: MovesenseStateChange(MovesenseDeviceState.tap),
  ),
  BackgroundTask(
    measures: [Measure(type: MovesenseSamplingPackage.ECG)],
    duration: const Duration(seconds: 30),
  ),
  movesense,
);

The trigger compares each STATE measurement with triggerCondition, and two state changes match when their state is the same.

{
  "__type": "dk.cachet.carp.movesense.state",
  "state": "tap",
  "timestamp": 1359384
}

Heart rate

HR streams the heart rate that the sensor computes from its ECG signal, from the Meas/HR resource.

MovesenseHR has these fields:

{
  "__type": "dk.cachet.carp.movesense.hr",
  "hr": 60.79999923706055,
  "rr": 976
}

ECG

ECG streams single-channel ECG at 125 Hz from the Meas/ECG/125 resource. Each measurement holds the batch of samples from one notification. The sensor supports other rates, but the package always uses 125 Hz.

MovesenseECG has these fields:

{
  "__type": "dk.cachet.carp.movesense.ecg",
  "timestamp": 40110192,
  "samples": [-240, -246, -241, -237, -232, -209, -179, -148, -129, -116, -98, -85, -80, -87, -87, -82]
}

Temperature

TEMPERATURE streams the temperature inside the sensor from the Meas/Temp resource, in kelvin. The package supports it on the Movesense MD only.

MovesenseTemperature has these fields:

{
  "__type": "dk.cachet.carp.movesense.temperature",
  "timestamp": 40112000,
  "measurement": 305
}

Motion

IMU streams the combined accelerometer, gyroscope and magnetometer resource Meas/IMU9/13 at 13 Hz, the lowest rate the sensor offers. Each measurement holds the samples from one notification.

MovesenseIMU has these fields:

Each sample has the fields x, y and z, of type num.

{
  "__type": "dk.cachet.carp.movesense.imu",
  "timestamp": 40110362,
  "accelerometer": [
    { "x": -0.0023929080925881863, "y": 9.150480270385742, "z": -3.2064969539642334 }
  ],
  "gyroscope": [
    { "x": -0.0023929080925881863, "y": 9.150480270385742, "z": -3.2064969539642334 }
  ],
  "magnetometer": [
    { "x": -0.0023929080925881863, "y": 9.150480270385742, "z": -3.2064969539642334 }
  ]
}