[PATCH/RFC] Change accelerometers to use ABS events rather than REL events.

Andy Green andy at openmoko.com
Wed Mar 11 08:20:07 CET 2009

Hash: SHA1

Somebody in the thread at some point said:

|> Either disabling one interrupt or having them both issue the same is a
|> valid solution to A5 situation.  On A6, we removed the pullup and have
|> the one interrupt drive push-pull.
| It's not clear to me that 'disabling' is an option.
| The closest seems to be a setting called "GND" which presumably ties
| the line to Ground.  Seeing the interrupt is active-low, that would be
| permanently asserted?

You can select it to drive a source that is disabled from ever
happening, obviously it's simpler to just get them to drive the same
source in lockstep.

| For wake-from-suspend we cannot do any tricks with polling.  We have
| to choose between wake-on-WUP_FF, or wake-on-CLICK.
| Fortunately there are two accelerometers so we can get all the
| functionality we are likely to want:

Well, there is one more version-and-cpu-related quirk.

On GTA02 A5, the INT1+INT2 net for the second accelerometer ends up on
EINT16 / GPG8.  Unfortunately on S3C2442, only EINT0-15 are usable as
wake sources.

On GTA02 A6+, we tried to fix this by bringing a copy of this interrupt
signal to EINT8 / GPG0 which is a wake source.  But, we stuck R1547 in
the way which is marked as NC on the schematic version I am looking at.
~ Presumably it really isn't fitted breaking this fix.

So only one accelerometer works for wake.

| When the CPU is running we could take the same approach.  Or we could
| conceivably program WUP_FF_2 to have the same threshold as the first
| click threshold.  Then when it fires, set a timer for an appropriate
| duration and poll the 'click' status after that duration.
| It might not be worth the effort though.

Not sure if or how the highpass filter can fit in there to allow
threshold to wake on tap or shake.

- -Andy
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