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,
Have you try setting GPIO direction to out before writing to it??? give a shot. follow: http://sites.google.com/site/bifferboard/Home/gpio On Fri, Mar 11, 2011 at 4:04 PM, Alexandru Caramida < alexandruc1723@yahoo.com> wrote:
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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Please paste the full log of what you typed on the console and also paste output of: strace <your full command> On Fri, Mar 11, 2011 at 4:04 PM, Alexandru Caramida <alexandruc1723@yahoo.com> wrote:
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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Try setting 3 Pins as Out (Clk, CS, MOSI (MasterDataOUT)) and 1 as IN for MISO (MasterDataIn) On Fri, Mar 11, 2011 at 3:08 AM, Kaustubh Ashtekar <ksashtekar@gmail.com> wrote:
Please paste the full log of what you typed on the console and also paste output of:
strace <your full command>
On Fri, Mar 11, 2011 at 4:04 PM, Alexandru Caramida <alexandruc1723@yahoo.com> wrote:
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,
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Hi, I have been exploring lilo bootloader last days, and i have a question: There is piece of code in file bootsect.S like this: ; jmpi go,INITSEG ; this line is commented out push es push #go retf i wonder if are there any benefits of replacing line jmpi go,INITSEG ; which, i think is more readable by push es push #go retf besides to make people confused? -- regards Andrzej Kardas http://www.linux.mynotes.pl
Hi.... Not a pro asm coder, but here's what I think... On Sun, Mar 13, 2011 at 04:03, Andrzej Kardas <andrzej-kardas@o2.pl> wrote:
i wonder if are there any benefits of replacing line
jmpi go,INITSEG ; which, i think is more readable
by
push es push #go retf
besides to make people confused?
hm, I just read about retf here: http://stackoverflow.com/questions/1396909/ret-retn-retf-how-to-use-them and.... I think, personally, the push-push-retf is more readable. By pushing the values into the stack and do far return, it's easy to interpret that "we jump into return value which we should find in stack" The readability I point here is more like "do goto vs don't do goto". Although in assembly, we're not forced to do everything structurally, but it's better to avoid it. Let me guess, the context of the above "retf" is to exit from somekind of "function"? -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
participants (6)
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Alexandru Caramida -
Andrzej Kardas -
Kaustubh Ashtekar -
Mulyadi Santosa -
Tirtha Ghosh -
Vic