linux-kernel - Re: [PATCH v2] lis3lv02d: Add STMicroelectronics lis331dlh digital accelerometer

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Message-ID: <CAK-9PRBDpxtrxZWL_x9Uz--GMWDN5anyB_fuKtLrvZcLoRR+FQ@mail.gmail.com>
Date:	Wed, 22 Aug 2012 16:09:22 +0530
From:	Chinmay V S <cvs268@...il.com>
To:	"AnilKumar, Chimata" <anilkumar@...com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"eric.piel@...mplin-utc.net" <eric.piel@...mplin-utc.net>,
	"jic23@....ac.uk" <jic23@....ac.uk>,
	"greg@...ah.com" <greg@...ah.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] lis3lv02d: Add STMicroelectronics lis331dlh digital accelerometer

Hmmm. Interesting. As i understand LIS331DLH provides 16bit data
irrespective of the full-scale/sensitivity configuration. Hence we
could effectively map +/-2G to +/-32768(signed 16bit 2's complement).
According to the current-patch right-shifting the register values by
4(i.e. reducing 16bit --> 12bit) will mean that we lose accuracy by
~1mG.

Clearly this will NOT affect use-case like display-orientation in
smart-phones, but surely medical and industrial applications WILL
benefit from the additional accuracy by utilising the entire 16-bit
resolution provided by LIS331DLH hardware.

I went through the LIS331DLH datasheet/application-note from
http://www.st.com/internet/analog/product/218132.jsp and i'm a bit
confused from your statement about +/-2G being 12bit data. Nowhere is
it mentioned that LIS331DLH provides +/-2G|+/-4G|+/-8G as 12|13|14 bit
data respectively. Then again i might be wrong...

-- 
regards
ChinmayVS
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