Best way to sync a WiFi station time to IOS time over WiFi?

Question

tlaritz OP

Created Apr ’22

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I've searched the web on this topic and can't find good info.

I have a device (an ESP32 Programmable System on a Chip) and I'd like to sync its clock to that of the iPhone. (I want to sync the clocks so that I correctly fuse/align data collected by the ESP32 with GPS location data from the iPhone GPS receiver.) My current approach is to use NTP to sync the ESP32's clock to "network time" (available from time.apple.com) just like (I believe) the iPhone is doing. But, I would have to test the accuracy of this method as I'd __like to __ achieve an accuracy on the order of 0.01 seconds. (FYI: the ESP32 ecosystem provides NTP functionality.)

I've considered syncing the ESP32 clock to GPS time (via an external GPS receiver) but I am told that GPS time is not available on IOS. Thus, I cannot use GPS time to correctly align/fuse measurement from the ESP32 with the iPhone.

Thanks.

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Answer 1

DTS Engineer OP

Apple

Apr ’22

I am told that GPS time is not available on iOS.

That is correct.

Keep in mind that the time values you get from standard iOS APIs, like gettimeofday, are under the control of the user. They can disable the Set Automatically option in Settings and then set the time to whatever they want. And that time is the time you get back from Core Location. So, if you want your iOS code and your accessory to agree about time, you’ll need to set that up yourself.

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