Configuring Metrics

By default, Swift SDK 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 .pulseRate before calling start():

import SmartSpectra

let sdk = SmartSpectraSDK.shared
sdk.config.requestedMetrics = SmartSpectraConfig.breathingMetrics + [.pulseRate]

Read Metrics

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

private let sdk = SmartSpectraSDK.shared

if let metrics = sdk.metrics {
    let breathingRate = metrics.breathing.rate.last?.value
    let chestTrace = metrics.breathing.upperTrace.last?.value
    let abdomenTrace = metrics.breathing.lowerTrace.last?.value
    let pulseRate = metrics.cardio.pulseRate.last?.value
}

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

Metric Update Patterns

SmartSpectraSDK.metrics exposes 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.

For example, sdk.metrics?.cardio.pulseRate.last?.value and sdk.metrics?.breathing.rate.last?.value may temporarily evaluate to nil 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 sdk.metrics?.face.expression.last 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 array 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 nil 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.

private var lastPulseRate: Double?

func pulseRateText(from metrics: Metrics?) -> String {
    if let pulse = metrics?.cardio.pulseRate.last(where: { $0.timestamp > 0 })?.value {
        lastPulseRate = pulse
        return "\(Int(pulse.rounded())) bpm"
    }

    guard let lastPulseRate else { return "-- bpm" }
    return "\(Int(lastPulseRate.rounded())) bpm"
}

Advanced

Request additional metrics only when your app needs them:

sdk.config.requestedMetrics = SmartSpectraConfig.breathingMetrics + [
    .pulseRate,
    .arterialPressureTrace,
    .hrv,
    .edaTrace,
    .faceLandmarks,
    .blinking,
    .talking,
    .expressions,
]

Read the advanced fields from the same metrics object:

if let metrics = sdk.metrics {
    let pressureTrace = metrics.cardio.arterialPressureTrace.last?.value
    let hrvRmssd = metrics.cardio.hrv.last?.rmssd

    let edaTrace = metrics.eda.trace.last?.value

    let faceLandmarks = metrics.face.landmarks.last?.value
    let blinking = metrics.face.blinking.last?.detected
    let talking = metrics.face.talking.last?.detected
    let expression = metrics.face.expression.last
}

Advanced Payload Types

The Swift SDK uses the generated Swift protobuf types. Requested advanced metrics populate these fields:

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

Cardio {
    pulseRate: [MeasurementWithConfidence]
    arterialPressureTrace: [MeasurementWithConfidence]
    hrv: [Hrv]
}

Hrv {
    rmssd: Double
    meanNn: Double
    sdnn: Double
    baevsky: Double
    timestamp: Int64
    confidence: Float
}

Eda {
    trace: [Measurement]
}

Face {
    landmarks: [Landmarks]
    blinking: [DetectionStatus]
    talking: [DetectionStatus]
    expression: [Expression]
}

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