From: Ned Forrester <nforrester-/d+BM93fTQY@public.gmane.org>
To: Cliff Brake <cliff.brake-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: PXA270 SPI + SD card
Date: Wed, 04 Nov 2009 18:27:14 -0500 [thread overview]
Message-ID: <4AF20DD2.2050101@whoi.edu> (raw)
In-Reply-To: <f96d234e0911041354p1f11e415g427ec9b74ff4d25b-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On 11/04/2009 04:54 PM, Cliff Brake wrote:
> On Wed, Nov 4, 2009 at 4:53 PM, Cliff Brake <cliff.brake-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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 (http://elm-chan.org/docs/spi_e.html).
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-/d+BM93fTQY@public.gmane.org
Oceanographic Systems Lab 508-289-2226
Applied Ocean Physics and Engineering Dept.
Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA
http://www.whoi.edu/
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next prev 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] ` <f96d234e0911041353o25aeee4aqbb482f162aaeac5f-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2009-11-04 21:54 ` Cliff Brake
[not found] ` <f96d234e0911041354p1f11e415g427ec9b74ff4d25b-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2009-11-04 23:27 ` Ned Forrester [this message]
2009-11-05 6:17 ` Baruch Siach
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