Re: [PATCH] lis3lv02d: add axes knowledge of HP Pavilion dv5 models

[Éric Piel]

Giuseppe Bilotta schreef:
> On Tue, Feb 10, 2009 at 10:39 PM, Giuseppe Bilotta
> <giuseppe.bilotta@xxxxxxxxx> wrote:
> > On Tue, Feb 10, 2009 at 11:10 AM, Pavel Machek <pavel@xxxxxxx> wrote:
> > > Yeah, that patch. Not sure what to do next... you could grab lis3
> > > manual and see if you can setup chip by hand to get better results...
> > As Eric pointed out, it looks definitely like an endianness problem,
> > although there are a few strange things which are happening at the
> > same time. Is the lis3 manual available online somewhere, or can I
> > request it to the mfgr?
>
> 'k, found it on the STMicroelectronics website. Reading the doc about
> LIS3LV02DL I see that WHO_AM_I should return 3Ah, but my sensor
> returns 3Bh. I'll see if I find the correct datasheet for this one
> instead, it might have info about the differences.
Ah, yes, that would explain a lots of things! Your chip is 8bits! The 
original reporter had not reported anything and I didn't pay attention 
to this "little" detail when comparing the specs.


> One thing that I noticed is that (modulo axis inversion) I'm able to
> use the sensor correctly if I set the thing to only use the high byte,
> totally discarding the lower byte:
> 	return *((s8*)(&hi));
> Maybe this sensor needs a different setup to return 12 instead of 8
> bits of information.
So you either have the lis302dl or the lis202dl (2 axes only):
http://www.st.com/stonline/products/literature/ds/12726/lis302dl.htm
http://www.st.com/stonline/products/literature/ds/13624/lis202dl.htm

I'd guess you have the one with 3 axes as all the axes had changing 
values. More optimistically I'll imagine that no HP laptop has the 2D 
chip, which unfortunately share the same who_am_i value.

So to get it working you need to change the lis3lv02d_read_16() function 
to only read the low byte and put the high byte to FFh if the high bit 
(80h) is set (I guess it's a signed integer). Then for completeness you 
need to put MDPS_MAX_VAL to 128.

Does it work?

Once this is verified, you should add a flag in the driver for the 
device to know whether it's 8bits or 12bits. This would be set at 
initialization according to the who_am_i value.

Eric
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