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RE: Peculiar Register Write problem



> > at the source for cf_init() and see what registers it
> > initializes. Cut and
> > paste into your code until the registers become properly writable.
>
>I already did that, cf_init () does nothing but call cf_hwr_init ()
>which is my driver initialization function.

[...]


> > Cirrus's other EDBs use GPIO pins to drive chip select
> > signals on various
> > hardware. Check in particular that you're setting up the data
> > direction
> > register for the GPIO pins correctly, I think this is a
>What does this have to do with it not working?  My code is the same
>whether it's in or out of the driver.  And as far as I can tell, nothing
>occurs from the time I call cf_init () until it returns.

If you literally mean that:

X()
cf_init()

fails, where

cf_init()
X()

works properly, then there is really no other possibility than that 
something is happening in cf_init().

The reason I think GPIO direction is a likely culprit is that if you've got 
a chip select on a pin that's configured as input, you can write to the 
driver latch for that GPIO reg without any problem, but the actual pin will 
be floating, and probably brought high by a pullup in the device it's 
supposed to be driving.

Do a debug print of the data direction registers (PxDDR) and data registers 
(PxDR) before and after cf_init and see if there is anything different.


-- Lewin A.R.W. Edwards
Embedded Engineer, Digi-Frame Inc.
Work: http://www.digi-frame.com/
Tel (914) 937-4090 9am-6:30pm M-F ET
Personal: http://www.larwe.com/ http://www.zws.com/

"Far better it is to dare mighty things, to win glorious triumphs, even 
though checkered by failure, than to rank with those poor spirits who 
neither enjoy much nor suffer much, because they live in the gray twilight 
that knows not victory nor defeat."
(Theodore Roosevelt)


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