Slightly off topic from original question, however I cannot help but asking 
this question;

"Can I pinmux in PRU?" The TRM says I have to be in privileged mode to write 
pinmux register. 

Sent from my iPad

> On Jul 2, 2014, at 1:33 AM, TJF <[email protected]> wrote:
> 
> Hi cowboy!
> 
> I confirm, GPIO high is 3.3V. Unconnected pins (input pins without resistor) 
> have about 0.8V.
> 
> Why don't you use the PWM devices for that task?
> 
> Anyway, P8_11 isn't connected to the PRUSS. This pin only works in GPIO mode 
> (mode 7) and I'm not sure if you can reach 50MHz that way.
> 
> The faster way is to use a PRU register pin and for that you have to choose 
> another pin (ie. P8_15 = GPIO-1/15 = PRU-0:r30.t15).
> 
> And why are you doing the pinmuxing by the device tree overlay? Instead do it 
> from your PRUSS code! Compile a minimal device tree overlay like
> 
> /*
> * pru dts file BB-BONE-PRU-00A0.dts
> */
> 
> /dts-v1/;
> /plugin/;
> / {
>   compatible = "ti,beaglebone", "ti,beaglebone-black";
> 
>   /* identification */
>   part-number = "BB-BONE-PRU";
>   version = "00A0";
>   exclusive-use =
>     "P8.15";
> 
>   fragment@0{
>     target = <&pruss>;
>     __overlay__ {
>       status = "okay";
>     };
>   };
> };
> 
> 
> 
> Then add to your PRUSS code (OCP master port must be enabled)
> 
>   MOV  r1, 0x44E10800  // CM pinmux address
>   LDI  r2, 0b1110      // mode 6, no resistor
>   SBBO r2, r1, 0x3C, 1 // set pinmuxing @ball 15 (= GPIO-1/15)
> 
> That's all. You'll have all your code in single source and you're much faster 
> in doing any testing.
> 
> Good luck!
> -- 
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