Re: McSPI3 on the BeagleBoard

[Philip Balister <philip@balister.org>]

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David Brownell wrote:
> On Tuesday 17 February 2009, Philip Balister wrote:
>> A number of people have tried using the McSPI3 interface with the spidev 
>> driver. Running the spidev_test program shows data coming out of the 
>> interface, but when we connect the SIMO to SOMI pins, the spidev_test 
>> program shows only 0's. Someone tried wiring SOMI to +volts and still 
>> only saw 0 read.
> 
> I took a quick glance, and the pinmuxing looks sort of OK if
> you ignore the names ... use the right balls, not XXX:
> 
> +       AE2_3430_MCSPI3_CLK,
> +       AG5_3430_MCSPI3_SIMO,
> +       AH5_3430_MCSPI3_SOMI,
> +       AF4_3430_MCSPI3_CS0,
> +       AG4_3430_MCSPI3_CS1,
> 
> I suggest you start with a more focussed patch, only setting
> up McSPI3.  For one thing, the MMC2 pinmuxing will interfere
> with this set of MCSPI3 configurations.
> 
> Also, start with a less aggressive bit rate than 48 MHz; that
> may be OK on a well designed board, but breadboards tend to
> show flakiness at much over 10 MHz.

OK, more results:

1) I do not intend for this to go into the kernel, well unless there is 
an outcry from beagle users :)


Steve Sakoman suggested I do the pinmux setup in u-boot and furnished me 
with a small u-boot patch. Using this patch and removing the pinmux 
stuff from the kernel patch lead to working spidev_test.

The 48 MHz is the max rate, spidev_test defaults to 500 kHz. (but it 
appears to work at 48 MHz also.

Thanks for taking a look at this!

Philip

PS: I love photos: http://www.flickr.com/photos/32615155@N00/3291304854/

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