From: "AnilKumar, Chimata" <anilkumar@ti.com>
To: Chinmay V S <cvs268@gmail.com>,
"carmine.iascone@st.com" <carmine.iascone@st.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"eric.piel@tremplin-utc.net" <eric.piel@tremplin-utc.net>,
"jic23@cam.ac.uk" <jic23@cam.ac.uk>,
"greg@kroah.com" <greg@kroah.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"broonie@opensource.wolfsonmicro.com"
<broonie@opensource.wolfsonmicro.com>,
"dmitry.torokhov@gmail.com" <dmitry.torokhov@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2] lis3lv02d: Add STMicroelectronics lis331dlh digital accelerometer
Date: Thu, 23 Aug 2012 10:00:54 +0000 [thread overview]
Message-ID: <331ABD5ECB02734CA317220B2BBEABC13EA1EA53@DBDE01.ent.ti.com> (raw)
In-Reply-To: <CAK-9PRD6FH=5g0SrVcw+81Witpo8zRfvnsmGaePaA4swjHWkSw@mail.gmail.com>
On Wed, Aug 22, 2012 at 22:24:10, Chinmay V S wrote:
> > Look at this application note which talks about the outdata values
> > for 2G range (page 12/31) http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/APPLICATION_NOTE/CD00215823.pdf
>
> Had been through the application note earlier. The table5 (on page 12)
> that you refer to, does NOT contradict either 12/16bit, as in all the
> examples the lower 4 bits are zero. So i don't see how one can assume
> from these examples that for +/-2G they one should consider 12/16bits.
> A nice side-effect of using 12|13|14bits for +/-2|4|8G is that the
> values returned by the driver are in mG in all the 3 modes.
>
> > Corresponding to the 4G and 8G I got the details form older
> > patches (SHIFT_ADJ_4G and SHIFT_ADJ_8G).
> > http://driverdev.linuxdriverproject.org/pipermail/devel/2010-November/009685.html
> >
> > We can easily interpret number of bits for 4G and 8G from 2G
> > information.
>
> Going through the code of this driver i can see what you are talking
> about. Depending on the full-scale-range the device is being
> configured for, the number of bits used to represent acceleration in
> the driver is changed.
>
> Again judging from the code, the driver is always returning
> acceleration at a constant accuracy i.e. 1mG in all the 3 modes
> (+/-2|4|8G)i.e.
> +/-2G is mode means value can be anywhere from +/-2048mG,
> (requiring 12bits.)
> +/-4G in the range of +/-4096mG, requiring 13bits.
> +/-8G i.e. +/-8192mG, requiring 14bits.
>
> Was this done...
>
> a. ...because LIS331DLH's theoretical MAX accuracy is ~1mG
> If yes, then using 12bits is fine.
>
Note from datasheet, "1LSb=4g/4096 at 12bit representation,
±2g Full-scale"
>From this I understood that ±2G full scale value is 12 bits.
That is one more reason to take 12bit value.
Regards
AnilKumar
next prev parent reply other threads:[~2012-08-23 10:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-22 6:30 [PATCH v2] lis3lv02d: Add STMicroelectronics lis331dlh digital accelerometer AnilKumar Ch
2012-08-22 7:48 ` Arnd Bergmann
2012-08-22 8:44 ` Chinmay V S
2012-08-22 9:00 ` AnilKumar, Chimata
2012-08-22 10:39 ` Chinmay V S
2012-08-22 15:40 ` AnilKumar, Chimata
2012-08-22 16:54 ` Chinmay V S
2012-08-23 10:00 ` AnilKumar, Chimata [this message]
2012-08-23 10:23 ` Chinmay V S
2012-08-23 11:15 ` AnilKumar, Chimata
2012-08-23 11:33 ` Chinmay V S
2012-08-28 5:45 ` AnilKumar, Chimata
2012-09-23 21:38 ` Éric Piel
2012-09-24 5:46 ` AnilKumar, Chimata
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