Thanks, William. Questions below

> On Oct 26, 2015, at 15:56 , William Hermans <yyrk...@gmail.com> wrote:
> 
> Yes.
> 
> cat /sys/bus/iio/devices/iio\:device0/in_voltageX_raw is single shot mode. If 
> you're running in continuous mode you need to read from /dev/iio:device. So 
> you get this "error" when attempting to use single shot channel files, when 
> the ADC is operating in continuous mode. 

I'm using it the same way I always have. On my other BBB running a 
3.8.13-bone68 kernel and an older Debian, I'm able to read it just fine with 
the BB-ADC dtbo loaded. As far as I know, I've never set anything to be 
continuous (or one-shot, for that matter).

How do I tell what mode it's in, and how do I change it?

> If I were you, I'd just use single shot mode, as ADC reads through iio is dog 
> slow. single-shot is around 5x or maybe slightly more - faster. iio *could* 
> be faster if you could figure out how the buffer is structured, and make it 
> very large( to cut down on system interrupts ). But if you need "fast" ADC, 
> you'd be better off using either mmap on the ADC registers directly, or use 
> the PRU's.

I don't need ADC faster than 100 Hz (on each of up to three channels). I'd love 
to move it to the PRU, but right now I'm using a library that downloads 
firmware to both PRU cores to bitbang LED control. I'll have to modify that to 
add my own ADC needs, and I'm not ready to do that right now.

I can consider using mmap; is there an example of this?

Thanks!

> 
> On Mon, Oct 26, 2015 at 3:18 PM, Rick Mann <rm...@latencyzero.com> wrote:
> Anyone have any advice on why I can't seem to read the ADC? Thanks!
> 
> --------------
> 
> What am I missing here?
> 
> # uname -r
> 3.8.13-bone72
> 
> # pwd
> /sys/bus/iio/devices/iio:device0
> 
> # ls
> dev  in_voltage0_raw  in_voltage1_raw  in_voltage2_raw  name  power/  
> subsystem@  uevent
> 
> # cat in_voltage0_raw
> cat: in_voltage0_raw: Device or resource busy
> 
> The fragment from my DTBO:
> 
>         fragment@6 {
>                 target = <&tscadc>;
>                 __overlay__ {
> 
>                         status = "okay";
>                         adc {
>                                 ti,adc-channels = <0 1 2>;
>                         };
>                 };
>         };
> 
> Thanks,
> 
> --
> Rick Mann
> rm...@latencyzero.com
> 
> 
> --
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-- 
Rick Mann
rm...@latencyzero.com


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