Hello Bill!

I'm dealing with PRU stuff since month, creating the libpruio 
<http://beagleboard.org/project/libpruio/> library.

Am Freitag, 31. Oktober 2014 18:00:03 UTC+1 schrieb Bill Gray:
>
> I'm wondering if there is some special way that one needs to access them 
> in order to get this low latency, or if they should be accessed through the 
> same registers as "normal" gpio pins?  By the normal registers I mean...
>
> GPIO_DATAIN
> GPIO_DATAOUT
> GPIO_CLEARDATAOUT
> GPIO_SETDATAOUT
>

For low latency GPIOs you need not access the GPIO subsystems over the OCP 
master port. Instead, write output to dedicated bits in register r30 and 
receive input in register r31 (after setting the pin mode accordingly). 
Find the related header pins by searching for pr1_pru0* and pr1_pru1*. Some 
of them are reserved for EMC2 and HDMI on the BBB. If your 12 pins are 
mixed (inputs and outputs), you should have a good chance to find free 
header pins for either of the PRUSS. 

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