Messages in this thread | | | Date | Wed, 11 Feb 2009 00:17:21 +0100 | From | Éric Piel <> | Subject | Re: [PATCH] lis3lv02d: add axes knowledge of HP Pavilion dv5 models |
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Giuseppe Bilotta schreef: > On Tue, Feb 10, 2009 at 10:39 PM, Giuseppe Bilotta > <giuseppe.bilotta@gmail.com> wrote: >> On Tue, Feb 10, 2009 at 11:10 AM, Pavel Machek <pavel@suse.cz> 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. Yeah, we accept also 3Bh for the who_am_i (see in hp_accel.c). The reporter who had a laptop with such chip never reported any problem and I didn't pay attention enough to notice those chips have only 8bits precision.
> 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 probably have a lis202dl (which has only two axes of 8bits each) or a LIS302DL (3 axes of 8 bits): http://www.st.com/stonline/products/literature/ds/13624/lis202dl.htm http://www.st.com/stonline/products/literature/ds/12726/lis302dl.htm
Unfortunately, the WHO_AM_I register returns 3Bh in both cases. I'd tend to imagine it's a three axes chip, but you can confirm that by just checking if Z has any meaningful value. You can then modify lis3lv02d_read_16() to only return the byte as low byte and the high byte as FFh if the high bit of the value is set (because I guess they are signed integers). You also have to change MDPS_MAX_VAL to 128, to get things completely right.
Once we have this sorted, we should add a flag to know if the current device is 8 bits or 12 bits, depending on the value of who_am_i. This would allow the driver to work fine with both type of chip.
Eric
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