[MinnowBoard] GPIO – blocked GPIO request

[Abdelghani Ouchabane]

On 13/05/16 19:42, John Hawley wrote:
> Only way I can think of to do would be from inside the kernel directly,
> as I don't think the registers for the GPIOs are exposed up through user
> space.  Worst case you can just go and read/write to the memory
> directly, but that always comes with the associated risks.
>
> You'll also note that there are 3 GPIO controllers on the MinnowBoard
> MAX / Turbot, encompassing 255 potential GPIOs.  The pins were mainly
> picked for their native (non-gpio) functionality, and as a result may
> not be anywhere near each other from a register perspective.
>
> For example pins 21,23,25 are on a different controller than the rest of
> the pins in the LSE.
>
> 	LSE Pins 21,23,25 are on
> 		GPIOs 82-125, platform/INT33FC:02, INT33FC:02:
>
> 	Rest of the LSE Pins are on
> 		GPIOs 154-255, platform/INT33FC:00, INT33FC:00:
>
> (noting the Linux GPIO numbering above is coming from a Linux 3.14
> kernel, add 256 to those numbers if you are on anything 3.18 or newer)
>
> If you aren't going through trying to toggle the lines simultaneously
> like you are suggesting by reading / writing the registers directly,
> it's going to come down to how quickly you need to toggle the lines for
> the protocol you are working on, as there's usually a (small) window
> where you can toggle things and have the hardware recognize it as being
> within the window for being right.
>
> - John
>
> On 05/12/2016 07:26 AM, Abdelghani Ouchabane wrote:
>> Hello,
>>    is it possible to toggle values of several GPIO lines at the same
>> time, such as a data and clock line.
>>
>> "Since several GPIO lines are often handily placed in the same register,
>> it is often actually possible to read or write 8, 16 or 32 GPIO lines at
>> the same time. By attaching hardware to lines in the same register."
>>
>> Thanks
>> Ghani
>>
>> This email has been scanned by Barracuda Networks.
>> _______________________________________________
>> elinux-MinnowBoard mailing list
>> elinux-MinnowBoard at lists.elinux.org
>> http://lists.elinux.org/mailman/listinfo/elinux-minnowboard
> _______________________________________________
> elinux-MinnowBoard mailing list
> elinux-MinnowBoard at lists.elinux.org
> http://lists.elinux.org/mailman/listinfo/elinux-minnowboard
Thanks a lot John