Accelerometer Data

Charles-Henri Gros charles-henri.gros+openmoko at
Mon Mar 23 03:39:13 CET 2009

Iain B. Findleton wrote:
> I have been playing a bit with the accelerometers on the FR appear to
> observe the following:
>    1) The time stamp on events appears to be unreliable, in the sense
> that the time difference
>        between sequential events is frequently negative, and appears
> also to be have erratically
>        by jumping an order of magnitude or 2 between sequentially
> available events.
>    2) It also appears to be relatively common that a SYN arrives before
> all 3 axis values are available,
>        making it hard to figure out the meaning of the data

I've seen that too; it seems that '0' readings are discarded.

>    3) There is a significant difference between the readings of the 2
> accelerometers when the FR
>         is just sitting there on the desk doing nothing.

You're taking into account the fact that they're oriented differently right?

>     4) When you move the FR about, the rate of reports being available
> appears to become very erratic,
>          in the sense that there are relatively long periods between
> reports.

A known issue in 2008.12.

echo 10 > /sys/devices/platform/lis302dl.1/threshold

> My questions are:
>     1) Is this a common situation with the FR (OM2008.12)
>     2) Is the device driver just buggy?
> Of course, I realize that my own code might be just buggy, but these
> features of the accelerometers
> appear in both my C++ and TCL code, and in the example programs from the
> wiki references with
> print statements inserted.
> Tks for any advice.


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