SPI over GPIO

[Alexandru Caramida]

Hello everyone,

I am trying to emulate an SPI interface using four GPIO pins. This is a desktop 
computer with linux 2.6.28 kernel.

The problem is I don't know if the pins are working. I read that if I have the 
sysfs support for the kernel (which I do :D) all I have to do
is enable the respectiv pin using 

echo N > /sys/class/gpio/export

And I would get a gpioN directory 

But I always get: "write error : invalid argument."

Is there some other option i need to enable first? The people I am working with 
assured me that these pins are not used by any other device and they haven't 
found anything to suggest that they were turned off manualy.

Please help,


      
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