Configuring Metrics

By default, Android measurements request the breathing metric set. Add pulse rate when your app needs a basic cardio value.

Breathing and Pulse

Request Metrics

Request the default breathing metrics plus PULSE_RATE before calling start():

import com.presagetech.smartspectra.proto.MetricTypesProto.MetricType
import com.presagetech.smartspectra.SmartSpectraConfig
import com.presagetech.smartspectra.SmartSpectraSdk

val sdk = SmartSpectraSdk.shared
sdk.config.requestedMetrics =
    SmartSpectraConfig.breathingMetrics + listOf(MetricType.PULSE_RATE)

Read Metrics

Read the latest breathing and pulse samples from SmartSpectraSdk.metrics:

sdk.metrics.observe(viewLifecycleOwner) { metrics ->
    val breathingRate = metrics?.breathing?.rateList?.lastOrNull()?.value
    val chestTrace = metrics?.breathing?.upperTraceList?.lastOrNull()?.value
    val abdomenTrace = metrics?.breathing?.lowerTraceList?.lastOrNull()?.value
    val pulseRate = metrics?.cardio?.pulseRateList?.lastOrNull()?.value
}

Set requestedMetrics = null to return to the default breathing-only set. Cardio fields are empty unless you request a cardio metric such as PULSE_RATE.

SmartSpectraSdk.metrics publishes the latest SDK metrics payload. Each payload contains the samples that became available since the previous metrics update; it is not guaranteed to contain every requested field every time.

Metric category	Examples	Expected cadence	Empty/null behavior
Peak/event-driven rate metrics	`breathing.rateList`, `cardio.pulseRateList`, `cardio.hrvList`	Updated when a new physiological event, cycle, or analysis window produces a value	Lists may be empty between valid updates during active capture
Frame-driven metrics	`face.expressionList`, `face.landmarksList`, `face.blinkingList`, `face.talkingList`, breathing trace lists	Updated near device frame cadence, with SDK callbacks rate-limited to about 30 Hz	Usually present more continuously when the metric is enabled and the input signal is valid

For example, metrics?.cardio?.pulseRateList?.lastOrNull()?.value and metrics?.breathing?.rateList?.lastOrNull()?.value may temporarily evaluate to null between valid updates. This is expected and does not mean capture stopped or the metric was disabled. By contrast, face expression samples are frame-driven, so metrics?.face?.expressionList?.lastOrNull() can appear continuously while face metrics are enabled and the face signal is valid.

Recommended UI handling:

Keep the last valid rate sample in app state and update it only when the list contains a new sample.
Show an initial loading or placeholder state until the first valid sample arrives.
Do not overwrite a displayed pulse rate or breathing rate with null only because one metrics payload has no new sample.
Clear retained values when a capture session starts, stops, or when your app intentionally changes the requested metric set.
Prefer sample timestamps, and stable when present, to decide whether a retained value is fresh enough for your UI.

var lastPulseRate: Double? = null

sdk.metrics.observe(viewLifecycleOwner) { metrics ->
    val pulse = metrics
        ?.cardio
        ?.pulseRateList
        ?.lastOrNull { it.timestamp > 0 }
        ?.value

    if (pulse != null) {
        lastPulseRate = pulse
        pulseRateLabel.text = String.format(Locale.ROOT, "%.0f bpm", pulse)
    } else if (lastPulseRate == null) {
        pulseRateLabel.text = "-- bpm"
    }
}

Advanced

Request additional metrics only when your app needs them:

sdk.config.requestedMetrics =
    SmartSpectraConfig.breathingMetrics + listOf(
        MetricType.PULSE_RATE,
        MetricType.ARTERIAL_PRESSURE_TRACE,
        MetricType.HRV,
        MetricType.EDA_TRACE,
        MetricType.FACE_LANDMARKS,
        MetricType.BLINKING,
        MetricType.TALKING,
        MetricType.EXPRESSIONS,
    )

Read the advanced fields from the same metrics stream:

sdk.metrics.observe(viewLifecycleOwner) { metrics ->
    val pressureTrace = metrics?.cardio?.arterialPressureTraceList?.lastOrNull()?.value
    val hrvRmssd = metrics?.cardio?.hrvList?.lastOrNull()?.rmssd

    val edaTrace = metrics?.eda?.traceList?.lastOrNull()?.value

    val faceLandmarks = metrics?.face?.landmarksList?.lastOrNull()?.valueList
    val blinking = metrics?.face?.blinkingList?.lastOrNull()?.detected
    val talking = metrics?.face?.talkingList?.lastOrNull()?.detected
    val expression = metrics?.face?.expressionList?.lastOrNull()
}

Advanced Payload Classes

Android uses the generated protobuf classes. Requested advanced metrics populate these fields:

Metrics {
    breathing: Breathing
    eda: Eda
    face: Face
    cardio: Cardio
}

Cardio {
    pulseRateList: List<MeasurementWithConfidence>
    arterialPressureTraceList: List<MeasurementWithConfidence>
    hrvList: List<Hrv>
}

Hrv {
    rmssd: Double
    meanNn: Double
    sdnn: Double
    baevsky: Double
    timestamp: Long
    confidence: Float
}

Eda {
    traceList: List<Measurement>
}

Face {
    landmarksList: List<Landmarks>
    blinkingList: List<DetectionStatus>
    talkingList: List<DetectionStatus>
    expressionList: List<Expression>
}

EDA may take longer to produce its first sample than breathing or cardio outputs. See Data Types for the complete protobuf schema.

Breathing and Pulse

Request Metrics

Read Metrics

Metric Update Patterns

Advanced

Advanced Payload Classes

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