[ECOS] Peculiar Register Write problem

[Trenton D. Adams]

The only PxDDR register I'm using (PEDDR) is already taken care of at
the beginning of my code.

> -----Original Message-----
> From: Lewin A.R.W. Edwards [ mailto:larwe@larwe.com ] 
> Sent: Wednesday, June 27, 2001 9:41 AM
> To: Trenton D. Adams; 'eCos discussion'
> Subject: RE: [ECOS] 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)
> 
>