* Re: hdc100x driver backport
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@ 2017-03-20 19:23 ` Alison Schofield
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From: Alison Schofield @ 2017-03-20 19:23 UTC (permalink / raw)
To: De Vos, Bart (EXT - BE/Antwerp); +Cc: matt.ranostay, linux-iio
On Mon, Mar 20, 2017 at 04:54:07PM +0000, De Vos, Bart (EXT - BE/Antwerp) wrote:
> Hi,
>
> I'm trying to backport the hdc100x driver to v3.10.
>
> Can you elaborate on the temperature offset, especially here:
> http://lxr.linux.no/linux+v4.10/drivers/iio/humidity/hdc100x.c#L239
>
> I see the goal is to have millidegrees, and as such I would expect an offset of -40000. I don't understand the numbers used here and the relationship between the two.
> If I read out the offset in runtime I got the value specified to 'val' on line 240.
>
> Thanks for your feedback.
>
> Kr,
> Bart.
Hi Bart,
Copying Matt Ranostay as he is the author/expert on this driver.
hdc100x temperature is calculated as:
(raw + offset) * scale / 1000
Here's a sample reading:
raw: 25443 scale: 2.517700195 offset: -15887.515151 resolution: 0.006350
Temperature 24057.846068
Hope that helps,
alisons
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