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From: Ned Forrester <nforrester-/>
To: Cliff Brake <>
Subject: Re: PXA270 SPI + SD card
Date: Wed, 04 Nov 2009 18:27:14 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 11/04/2009 04:54 PM, Cliff Brake wrote:
> On Wed, Nov 4, 2009 at 4:53 PM, Cliff Brake <> wrote:
>> Hello,
>> I'm trying to get a PXA270 to talk to a SD card via SPI.  Has anyone
>> else done this?

I haven't used an SD card, but...

>> One of the requirements is the CS stay low for the entire transaction.
>>  Can this be done with the PXA270 controlling the frame (CS) signal,
>> or is GPIO control typically required?

A GPIO is typically used.  The PXA2xx processors lack a
multi-chip-select function for SPI devices, so one has to use a GPIO if
more than one device is on the bus.  Back in 2.6.20, there was a
cs_control() call back to allow the pxa2xx_spi.c driver to control a
separately allocated GPIO line.  I think there is now a more generalized
procedure in the kernel to specify the GPIO that is to be used for each
device on the bus.

> Also, what SPI mode is typically used for SD?  Looks like 0 and 3 are
> the closest (

Not sure on that one.  I think there was a lot of discussion about that
a couple of years ago when someone was getting SD cards to work.  You
might want to search the archives if no one answers you directly.

Ned Forrester                                       nforrester-/
Oceanographic Systems Lab                                  508-289-2226
Applied Ocean Physics and Engineering Dept.
Woods Hole Oceanographic Institution          Woods Hole, MA 02543, USA

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  parent reply	other threads:[~2009-11-04 23:27 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-11-04 21:53 PXA270 SPI + SD card Cliff Brake
     [not found] ` <>
2009-11-04 21:54   ` Cliff Brake
     [not found]     ` <>
2009-11-04 23:27       ` Ned Forrester [this message]
2009-11-05  6:17       ` Baruch Siach

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