Is HomeKit Temperature Sensor Resolution ±0.5 °C ?

Question

Created Feb ’21

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Hi,
I am using Homebridge on Raspberry Pi platform to get temperature from my sensors. I successfully update temperature data from Raspberry Pi to HomeKit application on my iPhone. The problem is, even I update temperature value using 0.1 °C resolution (like 23.3, 23.4, 23.5, 23.6) HomeKit just shows this values 0.5 °C resolution (like 23.0, 23.0, 23.5, 23.5 respectively). Is there any way to decrease rosolution to 0.1 °C ?

Many thank for help.
Regards,

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Answer 1

AncientCoder OP

Feb ’21

The HomeKit Accessory Protocol (HAP) specifies a step value of 0.1 Celsius for Current Temperature (with the actual value as a float), so the HomeKit app should be displaying your value correctly. It's strange that you're getting 0.5 intervals: maybe there's some Step interval being applied elsewhere (Homebridge?) or a numeric type conversion issue?

Interestingly, HAP specifies a minimum value for Current Temperature as 0 degrees Celsius - which may have caused a few issues in Texas recently.

Regards,

Michaela

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Answer 2

maverickws OP

Sep ’22

I’m sorry but got to confirm this behavior, iOS 15.6.1, temperature sensor is throwing 25.74ºC, Home.app displays 25.5ºC, temperature rises above 25.75º and Home.app jumps to 26ºC. There is no such thing as 0.1 increments, and definitely it’s not because of the integration, the temperatures are being sent correctly and the Home.app behaves as expected for an app that only permits 0.5 variations. Can only say this is a very disappointing level of precision. Not using Homebridge.

edit: searching about it, it’s a known behavior (or should I say, known problem, known issue, known bug?) https://www.reddit.com/r/HomeKit/comments/uatay4/is_there_a_way_to_disable_the_rounded_to_05_values/

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