IBM HDAPS, I need a tip.

IBM HDAPS, I need a tip.

[Alejandro Bonilla Beeche]

Hi Guys,

I hope you all aren't sick about the topic. I have a quick question...

Thanks to development of the driver from some nice guys, we are able to
get data from the accelerometer. There is one problem. How do we
calibrate the values that are outputed from the userspace? All PC's get
a different value, and we can't really find the best solution. What is
the scientific and smartest way to do this?

i.e. of the driver output from the userspace.
abonilla@debian:~/hdaps/hdaps-dave-0.02
$ ./ibm_hdaps_userspace /dev/ibm_hdaps 
x_accel: 409
y_accel: 528
   temp: 47
  temp2: 47
unknown: 7

If I move the PC 45 deg right.(Looking from front the left side is
higher)

km_activity (keybd) = 0
km_activity (mouse) = 0
x_accel: 396
y_accel: 579
   temp: 47
  temp2: 47
unknown: 7


The thing is, people have different values, and I think they are also
different depending on where they are.

Another question for this kernel inclusion (heh) Should we use Sysfs or
should we use the userspace that outputs this data, else what is
recomended?

Thanks in advance,

.Alejandro

Re: IBM HDAPS, I need a tip.

[Alejandro Bonilla Beeche]

Second Try... ;-)

Anyone? 

.Alejandro


On Sun, 2005-07-31 at 19:53 -0600, Alejandro Bonilla Beeche wrote:
> Hi Guys,
> 
> I hope you all aren't sick about the topic. I have a quick question...
> 
> Thanks to development of the driver from some nice guys, we are able to
> get data from the accelerometer. There is one problem. How do we
> calibrate the values that are outputed from the userspace? All PC's get
> a different value, and we can't really find the best solution. What is
> the scientific and smartest way to do this?
> 
> i.e. of the driver output from the userspace.
> abonilla@debian:~/hdaps/hdaps-dave-0.02
> $ ./ibm_hdaps_userspace /dev/ibm_hdaps 
> x_accel: 409
> y_accel: 528
>    temp: 47
>   temp2: 47
> unknown: 7
> 
> If I move the PC 45 deg right.(Looking from front the left side is
> higher)
> 
> km_activity (keybd) = 0
> km_activity (mouse) = 0
> x_accel: 396
> y_accel: 579
>    temp: 47
>   temp2: 47
> unknown: 7
> 
> 
> The thing is, people have different values, and I think they are also
> different depending on where they are.
> 
> Another question for this kernel inclusion (heh) Should we use Sysfs or
> should we use the userspace that outputs this data, else what is
> recomended?
> 
> Thanks in advance,
> 
> .Alejandro

Re: IBM HDAPS, I need a tip.

[Lee Revell]

On Sun, 2005-07-31 at 22:56 -0600, Alejandro Bonilla Beeche wrote:
> Second Try... ;-)
> 
> Anyone? 

You're obviously getting different values because "moving the laptop
left to right" will produce a different acceleration every time.

So in order to calibrate it you need a readily available source of
constant acceleration, preferably with a known value.

Hint: -9.8 m/sec^2.

Lee

Re: IBM HDAPS, I need a tip.

[Jan Engelhardt]

>So in order to calibrate it you need a readily available source of
>constant acceleration, preferably with a known value.
>
>Hint: -9.8 m/sec^2.

Drop it out of the window? :)



Jan Engelhardt
-- 

Re: IBM HDAPS, I need a tip.

[Yani Ioannou]

Well don't forget there is a bios 'calibration' routine that you will
see on start up (especially if you are on a moving vehicle/train).
What is this calibration used for, and does it provide calibration
information to the windows driver? Could we use it somehow to help
solve this problem?

Yani

On 8/1/05, Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
> 
> >So in order to calibrate it you need a readily available source of
> >constant acceleration, preferably with a known value.
> >
> >Hint: -9.8 m/sec^2.
> 
> Drop it out of the window? :)
> 
> 
> 
> Jan Engelhardt
> --
>

Re: IBM HDAPS, I need a tip.

[Paulo Marques]

Jan Engelhardt wrote:
>>So in order to calibrate it you need a readily available source of
>>constant acceleration, preferably with a known value.
>>
>>Hint: -9.8 m/sec^2.
> 
> Drop it out of the window? :)

No, no. Constant gravity (like having the laptop sitting on the desk) 
"feels like" constant acceleration.

Dropping it out of the window should measure 0 m/sec^2, because the 
accelerometer is not working on an inertial referential (I hope this is 
the correct term in english...). For the accelerometer, this is just 
like the feeling of free falling inside an elevator: no gravity :)

-- 
Paulo Marques - www.grupopie.com

It is a mistake to think you can solve any major problems
just with potatoes.
Douglas Adams

Re: IBM HDAPS, I need a tip.

[linux-os (Dick Johnson)]

On Mon, 1 Aug 2005, Paulo Marques wrote:

> Jan Engelhardt wrote:
>>> So in order to calibrate it you need a readily available source of
>>> constant acceleration, preferably with a known value.
>>>
>>> Hint: -9.8 m/sec^2.
>>
>> Drop it out of the window? :)
>
> No, no. Constant gravity (like having the laptop sitting on the desk)
> "feels like" constant acceleration.
>
> Dropping it out of the window should measure 0 m/sec^2, because the
> accelerometer is not working on an inertial referential (I hope this is
> the correct term in english...). For the accelerometer, this is just
> like the feeling of free falling inside an elevator: no gravity :)
>
> --
> Paulo Marques - www.grupopie.com

You need a centrifuge or something that works like one. You can
make one and you can calibrate it using simple techniques. For
instance, you can swing the mass (laptop) over your head, round
and round with your arm. If the rate is such that the mass "just"
falls over the top, the 'G's at that point are zero. At the
bottom of the swing, the 'G's will be maximum. If you used a
fish-scale (spring-scale) to swing the whole thing, you could
measure its static weight, then observe the apparent weight
everywhere along the swing arc. If you don't have to go through
0 Gs, you can just swing the whole thing around horizontally
and observe the fish-scale. The 'G' load is exactly the indicated
weight / static weight.

As a relative measure, a 5.5 lb weight, swung through a 5ft
diameter, (2.5 ft radius) arc at such a speed that it "just"
falls through the top, exerts about 4 Gs (22 lb) at the bottom.
Don't accidentally hit something. Impact Gs may make your
experiment expensive.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
Warning : 98.36% of all statistics are fiction.
.
I apologize for the following. I tried to kill it with the above dot :

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Thank you.

Re: IBM HDAPS, I need a tip.

[Vojtech Pavlik]

On Mon, Aug 01, 2005 at 08:55:53AM -0400, linux-os (Dick Johnson) wrote:

> > Jan Engelhardt wrote:
> >>> So in order to calibrate it you need a readily available source of
> >>> constant acceleration, preferably with a known value.
> >>>
> >>> Hint: -9.8 m/sec^2.
> >>
> >> Drop it out of the window? :)
> >
> > No, no. Constant gravity (like having the laptop sitting on the desk)
> > "feels like" constant acceleration.
> >
> > Dropping it out of the window should measure 0 m/sec^2, because the
> > accelerometer is not working on an inertial referential (I hope this is
> > the correct term in english...). For the accelerometer, this is just
> > like the feeling of free falling inside an elevator: no gravity :)
> >
> > --
> > Paulo Marques - www.grupopie.com
> 
> You need a centrifuge or something that works like one. You can
> make one and you can calibrate it using simple techniques.

Not at all. It's enough to let the laptop lie on the table for [0,0]G
calibration, then put sequentially it on all the four sides for [-1,0]G,
[1,0]G, [0,1]G, [0,-1]G calibration.

>From these five measurements you have both the zero point and the
slopes, including a good error estimate.

I've done that before when toying with IMUs.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR

Re: IBM HDAPS, I need a tip.

[Dave Hansen]

On Mon, 2005-08-01 at 04:07 -0400, Yani Ioannou wrote:
> Well don't forget there is a bios 'calibration' routine that you will
> see on start up (especially if you are on a moving vehicle/train).

I've never seen that.  Could you please elaborate on what you see, and
when?

-- Dave

Re: IBM HDAPS, I need a tip.

[linux-os (Dick Johnson)]

On Mon, 1 Aug 2005, Vojtech Pavlik wrote:

> On Mon, Aug 01, 2005 at 08:55:53AM -0400, linux-os (Dick Johnson) wrote:
>
>>> Jan Engelhardt wrote:
>>>>> So in order to calibrate it you need a readily available source of
>>>>> constant acceleration, preferably with a known value.
>>>>>
>>>>> Hint: -9.8 m/sec^2.
>>>>
>>>> Drop it out of the window? :)
>>>
>>> No, no. Constant gravity (like having the laptop sitting on the desk)
>>> "feels like" constant acceleration.
>>>
>>> Dropping it out of the window should measure 0 m/sec^2, because the
>>> accelerometer is not working on an inertial referential (I hope this is
>>> the correct term in english...). For the accelerometer, this is just
>>> like the feeling of free falling inside an elevator: no gravity :)
>>>
>>> --
>>> Paulo Marques - www.grupopie.com
>>
>> You need a centrifuge or something that works like one. You can
>> make one and you can calibrate it using simple techniques.
>
> Not at all. It's enough to let the laptop lie on the table for [0,0]G
> calibration, then put sequentially it on all the four sides for [-1,0]G,
> [1,0]G, [0,1]G, [0,-1]G calibration.
>

Huh?  A laptop on the table is subjected to 1G on earth. If turned over,
is still subjected to 1G, although the sensor may show -1G. Unless
the correct k (calibration factor) is known, for each load direction,
it cannot be derived from +/- 1, the only readings you have, because
of the 1G bias of the load-cell itself.
A pair of load-cells mounted orthagonally, will show the accelleration
in 4 axis. However, you can't assume that if you held the mass at
a 45 degree angle, for instance, that both sensors would read
0.707 (cos 45) or that if at 90, one pair would read 0.0

You need to calibrate using real values. With a sping-scale, and
some room to swing the device, you can readily obtain some accurate
load values.

>> From these five measurements you have both the zero point and the
> slopes, including a good error estimate.
>
> I've done that before when toying with IMUs.
>
> --
> Vojtech Pavlik
> SuSE Labs, SuSE CR
>

Cheers,
Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
Warning : 98.36% of all statistics are fiction.
.
I apologize for the following. I tried to kill it with the above dot :

****************************************************************
The information transmitted in this message is confidential and may be privileged.  Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited.  If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to DeliveryErrors@analogic.com - and destroy all copies of this information, including any attachments, without reading or disclosing them.

Thank you.

Re: IBM HDAPS, I need a tip.

[Vojtech Pavlik]

On Mon, Aug 01, 2005 at 10:22:57AM -0400, linux-os (Dick Johnson) wrote:

> Huh?  A laptop on the table is subjected to 1G on earth. If turned over,
> is still subjected to 1G, although the sensor may show -1G. Unless
> the correct k (calibration factor) is known, for each load direction,
> it cannot be derived from +/- 1, the only readings you have, because
> of the 1G bias of the load-cell itself.

The MEMS accelerometer measures the projection of the
acceleration/gravity vector in two orthogonal directions.

If you place the notebook on a horizontal table, the projection of
gravity to both the directions measured will be zero, because the
gravity vector is orthogonal to both of the directions.

Thus for each direction you get the value at -1, 0, and +1 G, and that's
perfectly enough to get a calibration, as long as the accelerometer is
linear, which MEMSes to a reasonable degree are.

> A pair of load-cells mounted orthagonally, will show the accelleration
> in 4 axis. However, you can't assume that if you held the mass at
> a 45 degree angle, for instance, that both sensors would read
> 0.707 (cos 45) or that if at 90, one pair would read 0.0

Well, accelerometers are not load cells with a weight mounted to them,
that's the thing.

> You need to calibrate using real values. With a sping-scale, and
> some room to swing the device, you can readily obtain some accurate
> load values.

The Earth's gravity is a very well known real value.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR

Re: [Hdaps-devel] Re: IBM HDAPS, I need a tip.

[Jon Escombe]

>>Thanks to development of the driver from some nice guys, we are able to
>>get data from the accelerometer. There is one problem. How do we
>>calibrate the values that are outputed from the userspace? All PC's get
>>a different value, and we can't really find the best solution. What is
>>the scientific and smartest way to do this?
>>    
>>

I'm not convinced we need to get so hung up on the calibration. Sure, 
each laptop has somewhat different resting values - but surely what 
we're looking for is any rate of change in either the X or Y values 
thats over a predefined 'safe' threshold? (I would imagine that we're 
only going to find that safe threshold from some imaginative testing 
once we've got the head parking sorted....)

Just my 2p worth,
Jon.


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RE: [Hdaps-devel] Re: IBM HDAPS, I need a tip.

[Alejandro Bonilla]

> >>Thanks to development of the driver from some nice guys, we
> are able to
> >>get data from the accelerometer. There is one problem. How do we
> >>calibrate the values that are outputed from the userspace?
> All PC's get
> >>a different value, and we can't really find the best
> solution. What is
> >>the scientific and smartest way to do this?
> >>
> >>
>
> I'm not convinced we need to get so hung up on the calibration. Sure,
> each laptop has somewhat different resting values - but surely what
> we're looking for is any rate of change in either the X or Y values
> thats over a predefined 'safe' threshold? (I would imagine that we're
> only going to find that safe threshold from some imaginative testing
> once we've got the head parking sorted....)
>
> Just my 2p worth,
> Jon.

hard drive parking was already sorted out. We have a script that does this
and works great parking the heads.

The problem here is that we have 10 different models.

One will have 20 as X and the others will have 500 as x. Some will increment
in 20 when you move them 45Deg, and some will increment 50.

How can you determine from an shake, to a fall?

.Alejandro

Re: IBM HDAPS, I need a tip.

[Yani Ioannou]

On 8/1/05, Dave Hansen <dave@sr71.net> wrote:
> On Mon, 2005-08-01 at 04:07 -0400, Yani Ioannou wrote:
> > Well don't forget there is a bios 'calibration' routine that you will
> > see on start up (especially if you are on a moving vehicle/train).
> 
> I've never seen that.  Could you please elaborate on what you see, and
> when?
> 

Sorry it says diagnostics, not calibration, but the way it behaves
leads me to believe its doing some sort of calibration. If you boot up
your thinkpad, get rid of your bios splash screen (esc), and tilt the
thinkpad back and forth you will see something about IBM Active
Protection diagnostics running and a spinner. If you keep tilting the
notebook back and forth you can actually prevent the machine from
booting because this will fail after a while. Normally you won't see
it, I mainly notice it while in a train or car.

Yani

Re: [Hdaps-devel] Re: IBM HDAPS, I need a tip.

[Jon Escombe]

> hard drive parking was already sorted out. We have a script that does this
> and works great parking the heads.

Would have to disagree with you here. Jens' ATA7 parking code is a great 
start but we still have a couple of issues to address before it's usable 
for this purpose. (1) it only works on a subset of the devices that the 
Windows driver works for, and (2) we need a way to freeze the device for 
a short period so that the next I/O request doesn't wake it up before it 
hits the floor...

> The problem here is that we have 10 different models.
> 
> One will have 20 as X and the others will have 500 as x. Some will increment
> in 20 when you move them 45Deg, and some will increment 50.
> 
> How can you determine from an shake, to a fall?

If there really are devices with resting values of 20 then I would agree 
we have a problem. I've tried on a few different Thinkpads and have 
always seen resting values of several hundreds. If this is true for all, 
I would like to think we could estimate a sensible value that works for 
everyone...

Regards,
Jon.

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