CARP Documentation

AppleWatchDevice is a device configuration in the study protocol, and its settings are handed to the watch app over WatchConnectivity.

final watch = AppleWatchDevice(
  motionSamplingRate: 10,
  heartRateEnabled: true,
  locationEnabled: false,
  fileTransferInterval: const Duration(minutes: 15),
);

protocol.addConnectedDevice(watch, phone);

Sensors

Property	Default	What it collects
`motionEnabled`	`true`	Switch for the motion sensor
`accelerometerEnabled`	`true`	Raw acceleration, including gravity
`deviceMotionEnabled`	`true`	Attitude, gravity, rotation rate, user acceleration
`heartRateEnabled`	`true`	Heart rate via HealthKit
`batteryEnabled`	`true`	Battery level and charging state of the watch
`deviceInfoEnabled`	`true`	Watch model, watchOS version, paired phone
`locationEnabled`	`false`	Location, altitude, speed, course
`headingEnabled`	`false`	Compass heading and geomagnetic field
`bluetoothEnabled`	`false`	Nearby Bluetooth devices
`audioEnabled`	`false`	Switch for the microphone

Motion

AppleWatchDevice(
  motionEnabled: true,
  motionSamplingRate: 10,       // Hz
  accelerometerEnabled: true,
  deviceMotionEnabled: true,
)

Property	Default	Notes
`motionSamplingRate`	`10`	Sampling rate in Hz

motionSamplingRate is the setting with the largest effect on both battery life and data volume, and the two scale together:

Sound

Sound sensing is off by default and needs two switches: the microphone itself, and what to do with it.

AppleWatchDevice(
  audioEnabled: true,                 // switch
  ambientNoiseEnabled: true,          // decibel level
  audioClassificationEnabled: true,   // sound labels
  audioDutyCycleEnabled: true,
  audioActiveDuration: const Duration(minutes: 1),
  audioRestDuration: const Duration(minutes: 3),
)

Property	Default	Notes
`audioEnabled`	`false`	Switch — the two below do nothing without it
`ambientNoiseEnabled`	`true`	Sound pressure level in decibel
`audioClassificationEnabled`	`true`	Sound labels via Apple’s SoundAnalysis
`audioDutyCycleEnabled`	`true`	Alternate between analysing and resting
`audioActiveDuration`	1 minute	Length of the active phase
`audioRestDuration`	3 minutes	Length of the resting phase

Background runtime

AppleWatchDevice(
  backgroundSessionType: WatchBackgroundSessionType.microphone,
)

This setting allows the app to continue running in the background when the wrist is lowered.

Value	Background runtime	Trade-off
`microphone` (default)	Good	A silent capture session. Needs microphone permission and the `audio` background mode. No audio is stored.
`workout`	Best	An `HKWorkoutSession`. The longest and most reliable runtime, but it appears as a workout in the participant’s fitness apps and affects their activity rings.
`none`	None	Collects only in the foreground. For short, supervised sessions.

Transferring data to the phone

AppleWatchDevice(
  fileTransferInterval: const Duration(minutes: 15),
  transferMode: WatchTransferMode.incremental,
  deleteAfterTransfer: true,
)

Property	Default	Notes
`fileTransferInterval`	15 minutes	How often the watch hands data over
`transferMode`	`incremental`	Which records are included
`deleteAfterTransfer`	`true`	Delete transferred records from the watch

fileTransferInterval sets how fresh the data is. A shorter interval means less delay but more radio wake-ups on both devices. transferMode:

Value	Behaviour	When to use it
`incremental` (default)	Only records collected since the last successful transfer	Long-running studies. Bounded radio time and storage.
`all`	Every record in the database, every time	Recovery and debugging. Safe (duplicates are discarded by record id) but grows more expensive as the database grows.

deleteAfterTransfer keeps storage on the watch bounded. Setting it to false keeps a local backup on the watch, at the cost of ever-growing disk use — combined with transferMode: all, transfer cost grows without limit.

Phone-side and advanced settings

Property	Default	Notes
`saveToLocalAwareDatabase`	`false`	Also write received records to the AWARE database on the phone
`enableNativeLogging`	`false`	Verbose logging from the native AWARE framework
`awareServerUrl`	`null`	Let the watch upload directly to an AWARE server

saveToLocalAwareDatabase is a phone-side setting and is not forwarded to the watch. awareServerUrl points the watch at an AWARE server of your own, bypassing the phone and CARP entirely. Leave it null in a normal CARP study. enableNativeLogging is useful while bringing a study up: it makes the native AWARE framework print what it is doing to the Xcode console.

All properties

Property	Default
`label`	`null`
`awareServerUrl`	`null`
`motionSamplingRate`	`10`
`accelerometerEnabled`	`true`
`deviceMotionEnabled`	`true`
`motionEnabled`	`true`
`batteryEnabled`	`true`
`deviceInfoEnabled`	`true`
`heartRateEnabled`	`true`
`locationEnabled`	`false`
`headingEnabled`	`false`
`bluetoothEnabled`	`false`
`audioEnabled`	`false`
`ambientNoiseEnabled`	`true`
`audioClassificationEnabled`	`true`
`audioDutyCycleEnabled`	`true`
`audioActiveDuration`	`Duration(minutes: 1)`
`audioRestDuration`	`Duration(minutes: 3)`
`fileTransferInterval`	`Duration(minutes: 15)`
`transferMode`	`WatchTransferMode.incremental`
`deleteAfterTransfer`	`true`
`backgroundSessionType`	`WatchBackgroundSessionType.microphone`
`saveToLocalAwareDatabase`	`false`
`enableNativeLogging`	`false`

Getting Started

The Watch App

Core Concepts

Reference

Configuring the Watch

Sensors

Motion

Sound

Background runtime

Transferring data to the phone

Phone-side and advanced settings

All properties

​Sensors

​Motion

​Sound

​Background runtime

​Transferring data to the phone

​Phone-side and advanced settings

​All properties

Sensors

Motion

Sound

Background runtime

Transferring data to the phone

Phone-side and advanced settings

All properties