From: Christian Eggers <ceggers@arri.de>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
Hartmut Knaack <knaack.h@gmx.de>,
Lars-Peter Clausen <lars@metafoo.de>,
Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
linux-iio <linux-iio@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iio: light: as73211: Increase measurement timeout
Date: Wed, 9 Sep 2020 20:04:24 +0200 [thread overview]
Message-ID: <6187855.5mNlXCv1x4@n95hx1g2> (raw)
In-Reply-To: <CAHp75VeAoDaBtaSb0Qeb=kHPg6kGvx71_iL2snC5iHh4cKPhRA@mail.gmail.com>
On Wednesday, 9 September 2020, 18:58:39 CEST, Andy Shevchenko wrote:
> On Wed, Sep 9, 2020 at 6:45 PM Christian Eggers <ceggers@arri.de> wrote:
> > We found some sensors which are much slower (20% at room temperature)
> > than nominal. According to the data sheet, up to 27% is possible. Now I
> > add 33% to the nominal time out, hopefully this is enough.
>
> I'm wondering if this is a function of temperature.
> And if that has an actual thermistor inside...
I haven't designed the hardware, but I guess that clock generation is done
using an RC oscillator which depends on temperature. Temperature measurement
is possible, but I think the recommended way is to externally control the
integration time using the SYN pin and to get the actual number of RC cycles
from a register. But generating the required waveform for the SYN pin using a
uC general purpose timer seems challenging.
I wouldn't be surprised if the measurement results also depend on the exact
value of the supply voltage.
next prev parent reply other threads:[~2020-09-09 18:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-09 15:44 [PATCH] iio: light: as73211: Increase measurement timeout Christian Eggers
2020-09-09 16:58 ` Andy Shevchenko
2020-09-09 18:04 ` Christian Eggers [this message]
2020-09-13 9:39 ` Jonathan Cameron
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