Re: [Gumstix-users] Simple SPI C code - part2?

[Adam A K. <kumpf@MIT.EDU>]

Hi Tim,

Thanks for the link.  That seems to be in the right directions, although, t=
he
driver is specific to a parallel port implementation. (it shifts bits in an=
d
out of two pins on the parallel port).  The pxa2xx used with the GumStix ha=
s
some built-in functionality for SPI that should allow an entire byte to be
placed in memory somewhere and then it will be pushed out, with on-chip
dedicated hardware, to the SPI bus in a serial manner. (not a bit-shifting =
for
loop)

as a side note, when I "cat /proc/iomem" I get this:
04000300-040fffff : smc91x-regs
04000300-0400030f : smc91x
40301680-403016a3 : pxa2xx-i2c.0
40400000-40400083 : pxa2xx-i2s
40600000-4060ffff : pxa2xx-udc
41100000-41100fff : pxa2xx-mci
41100000-41100fff : pxa2xx-mci
41400000-4140002c : pxa2xx-spi.2   <------ good?
44000000-4400ffff : pxa2xx-fb
a0000000-a3ffffff : System RAM
a0017000-a01580b3 : Kernel text
a015a000-a0198867 : Kernel data

If I knew exactly what to put in the pxa2xx-spi.2 memory locations, I may b=
e
getting close to an idea...  This all feels like such a hack though, and no=
t a
well supported solution.

Has _ANYONE_ gotten SPI up and running yet?  All I've been able to find via
forums/wiki/google/etc. are people trying SPI on the pxa2xx/GumStix without
success.

- Adam Kumpf
ku...@mi...






Quoting Tim Newsom <ce...@ya...>:

>
>
> Adam A Kumpf <kumpf@MIT.EDU> wrote: I'm working on a multi-gumstix 
> robotics project and getting the SPI
> port working
> is a very important part so that the gumstixs can talk to daughter-board
> dsps/PICs/other specialized hardware.
>
> I've been trying to figure out the NSSP SPI driver setup for quite a
> while now,
> but I keep getting stuck.  If someone who knows the inner-workings of
> the linux
> kernel/drivers I would really appreciate some help.
>
> Here is what I "think" I know so far about the SPI setup...
> - 2.6.17gum has the foundation for SPI support
> - pxa2xx-spi doesn't come loaded in the kernel, but it can be easily buil=
t-in
> with menuconfig in the 2.6.17gum directory.
> - 2.6.17gum/arch/mach-pxa/gumstix.c can modified to setup the NSSP 
> SPI port on
> startup, along with a listing of slave devices. (maybe more can be done
> here?!?)
> - now the bindings for pxa2xx-SPI are in place, but the hardware cannot
> be used
> without a driver.
> - A "characer device" driver should fill the gap by allowing a 
> "/dev/spi" node
> for the SPI device.  This allows the user to interact with the calls now
> embedded in the kernel.
> - programs should now be able to read/write/setup(via ioctl) the SPI port=
 via
> its device node.
>
> I am stuck on how to go about making the character device driver.  In
> particular, I do not know how to make the driver link to the SPI port.  I=
've
> looked through some simple character drivers that write kernel messages a=
nd
> create device nodes and all is well.. but how do I modify that to actuall=
y
> interact with the NSSP SPI hardware port?
>
> Ideally, a "/dev/spi" device would be created with default parameters 
> when the
> gumstix boots and then programs could simply read/write to the device.
>
> I appreciate all of your feedback to help get SPI actually up and running=
! :)
>
> - Adam Kumpf
> ku...@mi...
>
>
> ok, So I was just looking into this and I found a few places which 
> have examples and might help but I con only find one of them for some 
> reason.
>
> This is an SPI driver by someone which at this point may already be 
> part of the kernel (I have not looked and I think code already exists 
> there) but the important thing is the code showing how to interface 
> user land code with the SPI module.
>
> http://www.paul.de/downloadables/  Look at SPI-DRIVER and if you get 
> version 2.0 it might work.  I have not tested any of this, just been 
> doing research.
>
> Its a very simple example so if it works, great.
>
> --Tim.
>
>
> ---------------------------------
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