From: "Paweł Jarosz" <paweljarosz3691@gmail.com>
To: Laxman Dewangan <ldewangan@nvidia.com>
Cc: linux-iio@vger.kernel.org, rui.zhang@intel.com, edubezval@gmail.com
Subject: Re: [PATCH] thermal: generic-adc: Fix linear temperature approximation
Date: Thu, 20 Oct 2016 19:26:03 +0200 [thread overview]
Message-ID: <bd01678c-5cf4-e50c-2dff-5aea04040e29@gmail.com> (raw)
In-Reply-To: <5808F86A.4080800@nvidia.com>
> It is Negative Coefficient Thermistor (NCT) and so adc reads are
> different.
> Lower temp gives higher value.
>
> So table should be
>
> <7000 10
> 9000 8>;
>
> temp1 = gti->lookup_table[2 * i];
> temp2 = gti->lookup_table[2 * i - 2];
>
> and then use in following equation.
>
>>
>> adc_hi = gti->lookup_table[2 * i - 1];
>> adc_lo = gti->lookup_table[2 * i + 1];
>> temp = gti->lookup_table[2 * i];
>> temp -= (val - adc_lo) * (temp1 - temp2) / (adc_hi - adc_lo);
val = 9
adc_hi = 10
adc_lo = 8
temp = 9000 - (9 - 8)*(7000 - 9000)/(10 - 8)
temp = 9000 - (1)*(-2000)/(2)
temp = 9000 - (-1000) = 10000
still wrong ... temp for val = 9 should be 8000
Maybe we could leave this patch as it is?
Paweł
next prev parent reply other threads:[~2016-10-20 17:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-18 19:31 [PATCH] thermal: generic-adc: Fix linear temperature approximation Paweł Jarosz
2016-10-20 12:40 ` Laxman Dewangan
2016-10-20 14:56 ` Paweł Jarosz
2016-10-20 15:49 ` Laxman Dewangan
2016-10-20 16:14 ` Paweł Jarosz
2016-10-20 16:01 ` Laxman Dewangan
2016-10-20 17:10 ` Paweł Jarosz
2016-10-20 17:01 ` Laxman Dewangan
2016-10-20 17:26 ` Paweł Jarosz [this message]
2016-10-21 6:18 ` Laxman Dewangan
2016-10-21 7:00 ` Paweł Jarosz
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