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From: Conor Dooley <conor@kernel.org>
To: Jonathan Cameron <jic23@kernel.org>
Cc: Alisa-Dariana Roman <alisadariana@gmail.com>,
	michael.hennerich@analog.com, linux-iio@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	alexandru.tachici@analog.com, lars@metafoo.de, robh@kernel.org,
	krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
	lgirdwood@gmail.com, broonie@kernel.org, andy@kernel.org,
	nuno.sa@analog.com, marcelo.schmitt@analog.com,
	bigunclemax@gmail.com, dlechner@baylibre.com,
	okan.sahin@analog.com, fr0st61te@gmail.com,
	alisa.roman@analog.com, marcus.folkesson@gmail.com,
	schnelle@linux.ibm.com, liambeguin@gmail.com
Subject: Re: [PATCH v7 5/6] dt-bindings: iio: adc: ad7192: Add AD7194 support
Date: Mon, 6 May 2024 16:54:17 +0100	[thread overview]
Message-ID: <20240506-evaluate-darkroom-b0f8a7bf4598@spud> (raw)
In-Reply-To: <20240505204602.5d4cbfa0@jic23-huawei>

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On Sun, May 05, 2024 at 08:46:02PM +0100, Jonathan Cameron wrote:
> On Tue, 30 Apr 2024 18:21:01 +0100
> Conor Dooley <conor@kernel.org> wrote:
> 
> > On Tue, Apr 30, 2024 at 07:29:45PM +0300, Alisa-Dariana Roman wrote:
> > > +      diff-channels:
> > > +        description:
> > > +          Both inputs can be connected to pins AIN1 to AIN16 by choosing the
> > > +          appropriate value from 1 to 16.
> > > +        items:
> > > +          minimum: 1
> > > +          maximum: 16
> > > +
> > > +      single-channel:
> > > +        description:
> > > +          Positive input can be connected to pins AIN1 to AIN16 by choosing the
> > > +          appropriate value from 1 to 16. Negative input is connected to AINCOM.
> > > +        items:
> > > +          minimum: 1
> > > +          maximum: 16  
> > 
> > Up to 16 differential channels and 16 single-ended channels, but only 16
> > pins? Would the number of differential channels not max out at 8?
> 
> May not really be limited to 16 differential. Many chips use general purpose
> muxes on both sides so you can do all combinations. In practice that's normally
> pointless.
> 
> A more useful case is to do all but one channel as positive inputs and the remaining
> channel as the negative for those 15 differential channels.

Yah, 15 is what I had in my head as the highest reasonable number given
the information given about the AIN# pins.

> This is effectively the same as doing pseudo differential channels, but
> on more flexible hardware.  This is in contrast to a device that only supports
> pseudo differential where there is a special pin for the negative
> (this device has that as well as full muxes on the other 16 lines).
> 
> Having said all that.  The ad7194 datasheet says 8 differential channels..
> I have no idea why though... Maybe something to do with the mux switching?
> Or maybe assumption is that if you want to do pseudo differential you'll use
> the pseudo differential mode rather than wasting hardware?

I didn't look at the datasheet tbf, I was just asking given the
description didn't make sense to me and looking for an explanation from
the author.

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  reply	other threads:[~2024-05-06 15:54 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-30 16:29 [PATCH v7 0/6] iio: adc: ad7192: Add AD7194 support Alisa-Dariana Roman
2024-04-30 16:29 ` [PATCH v7 1/6] iio: adc: ad7192: Use standard attribute Alisa-Dariana Roman
2024-04-30 16:29 ` [PATCH v7 2/6] dt-bindings: iio: adc: ad7192: Add aincom supply Alisa-Dariana Roman
2024-04-30 16:29 ` [PATCH v7 3/6] " Alisa-Dariana Roman
2024-04-30 20:28   ` Andy Shevchenko
2024-05-01 16:54   ` David Lechner
2024-04-30 16:29 ` [PATCH v7 4/6] dt-bindings: iio: adc: Add single-channel property Alisa-Dariana Roman
2024-04-30 17:15   ` Conor Dooley
2024-04-30 16:29 ` [PATCH v7 5/6] dt-bindings: iio: adc: ad7192: Add AD7194 support Alisa-Dariana Roman
2024-04-30 17:21   ` Conor Dooley
2024-05-05 19:46     ` Jonathan Cameron
2024-05-06 15:54       ` Conor Dooley [this message]
2024-05-10 10:05     ` Alisa-Dariana Roman
2024-05-10 14:21       ` David Lechner
2024-05-10 21:26         ` Conor Dooley
2024-05-11 11:29           ` Jonathan Cameron
2024-04-30 17:26   ` Conor Dooley
2024-04-30 16:29 ` [PATCH v7 6/6] " Alisa-Dariana Roman
2024-04-30 20:33   ` Andy Shevchenko
2024-05-01 17:54   ` David Lechner
2024-05-06 13:39   ` Jonathan Cameron
2024-04-30 17:19 ` [PATCH v7 0/6] " Conor Dooley

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