linux-kernel - Re: ncpXXxh103 compensation values?

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Message-ID: <20160330205958.GA21993@roeck-us.net>
Date:	Wed, 30 Mar 2016 13:59:58 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Maxime Jayat <jayatmaxime@...il.com>
Cc:	Joseph McNally <jmcna06@...il.com>,
	Jean Delvare <jdelvare@...e.de>, lm-sensors@...sensors.org,
	linux-kernel@...r.kernel.org
Subject: Re: ncpXXxh103 compensation values?

Hi Maxime,

On Wed, Mar 30, 2016 at 05:58:41PM +0200, Maxime Jayat wrote:
> I don't think it is wrong to use ncpXXxh103 instead of ncp15xh103,
> because the first number refers to the physical size of the thermistor
> and should not change its behavior. In fact the datasheet does the same
> kind of grouping.
> 
> I was just wondering what was the reason for the discrepancy between the
> datasheet and your values.
> Indeed the datasheet I linked earlier, at page 15, gives you verbatim
> the content of this array and the result of your calculation does not
> match it.
> It is not _absurdly_ wrong but, at first sight, it seems like there is a
> 10 degrees difference at the extremes (but 10 kOhm at 25 C is correct).
> 

Can the two of you sort this out and send me a fixup patch if necessary ?

Thanks,
Guenter

p.s.: Please don't top-post.

> Le 30/03/2016 17:09, Joseph McNally a écrit :
> > Hello Maxime,
> > 
> > This data was calculated for a Murata NCP15XH103XXXXX.
> > 
> > You have illustrated something to me with your question though. When I
> > uploaded this patch, I was following the format of the compensation
> > tables that are already present in the file. So i used "ncpXXxh103"
> > instead of "ncp15xh103". Also, it was my first patch submitted to the
> > Linux kernel. So I may have been over thinking some things! With some
> > hindsight, I see that the name is misleading. I'm going to have to
> > revisit this patch to make it more 'generic' for other thermistors, or
> > make it more specific for this particular thermistor.
> > 
> > I hope that answers your questions. Thanks for pointing this out to me.
> > 
> > Regards,
> > Joseph
> > 
> > On Wed, Mar 30, 2016 at 3:03 PM, Maxime Jayat <jayatmaxime@...il.com
> > <mailto:jayatmaxime@...il.com>> wrote:
> > 
> >     Hello Joseph,
> > 
> >     You recently added support for the ncpXXxh103 in
> >     drivers/hwmon/ntc_thermistor.c with the following array of values:
> > 
> >     +static const struct ntc_compensation ncpXXxh103[] = {
> >     +       { .temp_c       = -40, .ohm     = 247565 },
> >     +       { .temp_c       = -35, .ohm     = 181742 },
> >     +       { .temp_c       = -30, .ohm     = 135128 },
> >     +       { .temp_c       = -25, .ohm     = 101678 },
> >     +       { .temp_c       = -20, .ohm     = 77373 },
> >     +       { .temp_c       = -15, .ohm     = 59504 },
> >     +       { .temp_c       = -10, .ohm     = 46222 },
> >     +       { .temp_c       = -5, .ohm      = 36244 },
> >     +       { .temp_c       = 0, .ohm       = 28674 },
> >     +       { .temp_c       = 5, .ohm       = 22878 },
> >     +       { .temp_c       = 10, .ohm      = 18399 },
> >     +       { .temp_c       = 15, .ohm      = 14910 },
> >     +       { .temp_c       = 20, .ohm      = 12169 },
> >     +       { .temp_c       = 25, .ohm      = 10000 },
> >     +       { .temp_c       = 30, .ohm      = 8271 },
> >     +       { .temp_c       = 35, .ohm      = 6883 },
> >     +       { .temp_c       = 40, .ohm      = 5762 },
> >     +       { .temp_c       = 45, .ohm      = 4851 },
> >     +       { .temp_c       = 50, .ohm      = 4105 },
> >     +       { .temp_c       = 55, .ohm      = 3492 },
> >     +       { .temp_c       = 60, .ohm      = 2985 },
> >     +       { .temp_c       = 65, .ohm      = 2563 },
> >     +       { .temp_c       = 70, .ohm      = 2211 },
> >     +       { .temp_c       = 75, .ohm      = 1915 },
> >     +       { .temp_c       = 80, .ohm      = 1666 },
> >     +       { .temp_c       = 85, .ohm      = 1454 },
> >     +       { .temp_c       = 90, .ohm      = 1275 },
> >     +       { .temp_c       = 95, .ohm      = 1121 },
> >     +       { .temp_c       = 100, .ohm     = 990 },
> >     +       { .temp_c       = 105, .ohm     = 876 },
> >     +       { .temp_c       = 110, .ohm     = 779 },
> >     +       { .temp_c       = 115, .ohm     = 694 },
> >     +       { .temp_c       = 120, .ohm     = 620 },
> >     +       { .temp_c       = 125, .ohm     = 556 },
> >     +};
> >     +
> > 
> >     Where are these taken from?
> >     Unlike the other thermistors in the file, these values don't seem to
> >     match anything in the Murata NTC Thermistor Datasheet.
> >     See:
> >     http://www.murata.com/~/media/webrenewal/support/library/catalog/products/thermistor/ntc/r44e.ashx
> > 
> >     --
> >     Maxime Jayat
> > 
> > 
> -- 
> Maxime Jayat