Re: [PATCH 0/2] iio: ti_am335x_adc: Add optional DT properties for tscadc
From: Vignesh R
Date: Tue Apr 14 2015 - 08:03:30 EST
On Tuesday 14 April 2015 04:46 PM, Hannes Petermaier wrote:
> Hi Vignesh,
> did you recognize my last email ? whats your opinion around that =
> best regards,
> ----- Forwarded by Hannes Petermaier/Eggelsberg/AT/B&R on 14.04.2015 13:14
> Hannes Petermaier/Eggelsberg/AT/B&R schrieb am 07.04.2015 14:30:19:
>> From: Hannes Petermaier/Eggelsberg/AT/B&R
>> To: vigneshr@xxxxxx
>> Cc: linux-iio@xxxxxxxxxxxxxxx
>> Date: 07.04.2015 14:30
>> Subject: WG: Fwd: [PATCH 0/2] iio: ti_am335x_adc: Add optional DT
> properties for tscadc
>> Hi Vignesh,
>> would it be possible to add some more channel-specific settings ?
>> It would be nice to have allmost full control to the STEPCONFIGx
>> At least we need to write the bits
>> In the current mainline version only (SEL_INP_SWC_3_0) is written.
>> So for the other bits "0" is value is used, for my point of view this is
> not correct.
>> For example if we want to read a value from AIN5 the negative pin from
> adc is
>> muxed allways to AIN0.
Sorry... I didn't understand what you meant by"AIN5 is muxed always with
>> In fact i can readout heavy jitter even if AIN5 is connected to ground -
>> setting up negative adc pin within code (to use REFN) the readout value
> is 0
>> as expected without nameable jitter.
>> If i short AIN0 also to ground, jitter is also eliminated.
Hmmm... nobody has reported such behavior before. ADC support for
am335x-evm/beaglebone has been there for quite long time, but nobody
reported any jitter on AIN5 line. I think this may be specific to
your setup. Can you provide more info with regard to your setup?
Which kernel? Is it am335x-evm or beaglebone or a custom board?
>> Maybe this is also some fault of TI SoC ... in normal case somebody
>> expect, that negative adc pin is equal even the Diff_CNTRL bit isn't set
> - but
>> in practice it isn't.
>> Also actually it isn't possible to make some accurate measurement due to
>> fact that allways VDDA_ADC is used as positive reference.
>> So it would be nice to have control around this bits.
>> Whats your opinion around that?
Sorry, I am not yet clear on your bug/use-case.
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