Problems Reading Accelerometer Device

Andy Green andy at openmoko.com
Wed Nov 26 11:43:45 CET 2008


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Somebody in the thread at some point said:
| Hi,
|
| I want to read out the Acc device and for me it is important to get
| really every measurement.
|
| I read the wiki and the gestures source code but it didnt't help.
|
| I set the samplerate to 400 Hz and though I think the time between two
| (x y z separator) measurements should be ca 2,5 ms, but in my logfile
| you can see that there are sometimes 30 ms. So I think I loose some
values.
|
| Any idea what I'm doing wrong?

Probably nothing, some other driver with higher interrupt priority can
be blocking service for 30ms enforcing latency... not sure what to
recommend about identifying which one unfortunately.

There's an extremely ugly trick possible to use FIQ to force-service
- -or-see-not-ready both accels at say 2ms period that will guarantee full
coverage but it's pretty bad.

- -Andy
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