linux-kernel - Re: [PATCH 5/5] iio: adc: ad7606: add gain calibration support

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Message-ID: <okavvmsyg6jpdleye5e5oxg2cwwgkr42f6wlq2dlsswrzxkpnq@66apz7uva5eg>
Date: Thu, 1 May 2025 15:49:44 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	David Lechner <dlechner@...libre.com>, Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 5/5] iio: adc: ad7606: add gain calibration support

On 30.04.2025 01:34, Andy Shevchenko wrote:
> On Tue, Apr 29, 2025 at 4:08 PM Angelo Dureghello
> <adureghello@...libre.com> wrote:
> >
> > From: Angelo Dureghello <adureghello@...libre.com>
> >
> > Add gain calibration support, using resistor values set on devicetree,
> > values to be set accordingly with ADC external RFilter, as explained in
> > the ad7606c-16 datasheet, rev0, page 37.
> >
> > Usage example in the fdt yaml documentation.
> 
> ...
> 
> > +#define AD7606_CALIB_GAIN_MIN  0
> > +#define AD7606_CALIB_GAIN_STEP 1024
> > +#define AD7606_CALIB_GAIN_MAX  65536
>
Hi Andy,
 
> Are those values in decimal in the datasheet?
> It looks to me something like
> 
> _MAX = (64 * _STEP)
> 
> but is it for real? Usually values are limited by the amount of bits
> in the HW, here it spans over 65 steps, i.e. 7 bits would be needed...
> Confusing.
>

true, thanks,
there must be a typo in the datasheet that says 0 to 65536 with a
step of 1024 with 6 bits. Only 0 to 63 are possbile here.

step 0 = 0
step 63 = 64512
 
Will fix that.

Regards,
angelo

> -- 
> With Best Regards,
> Andy Shevchenko