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I am currently working on building an app that sends measurements from apple watch series 2 (watchOS 3), using coremotion and 50Hz frequency.

Currently, the data is sent using WatchConnectivity-messages to the iPhone. Each message equals a single measurement. When measuring is done, a csv file is created and emailed using the iPhone.

My main concern: What frequency of messages can WatchConnectivity handle? Should i create batch message (array of strings to con-cat several measurements), or can i keep sending 1 message per measurement (~3000 messages per minute).

Currently i am only taking 1 attribute from devicemotion, later on i will be using several, which means multiply the ~3000 measurements a minute by the number of attributes.

Any thoughts?

Thanks Ariel

Ariel Nitzan
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2 Answers2

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After some experiments, i found that using batch is much preferable. Regarding exact frequency of transmission - unknown. Enjoy

Ariel Nitzan
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Through some experimentation I've found that WatchConnectivity lets you have 10 messages in flight at any points in time, so batching will definitely be necessary.

Unless you need the data to show "live" in the UI on the phone I'd suggest batching and writing the data to files on the watch and using the transferFile API to send the items.

ccjensen
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  • for the type of data i transfer i can live with a [[Double]] 2d array, nothing fancy. Thanks for checking the limit! had no idea it's 10. – Ariel Nitzan Mar 20 '17 at 18:32