[Cryptech Tech] never do in software what can be done in hardware

Benedikt Stockebrand bs at stepladder-it.com
Wed Oct 1 06:09:52 UTC 2014

Hi Fredrik and list,

Fredrik Thulin <fredrik at thulin.net> writes:

>> I have a somewhat similar idea over here: Use a GPIO pin on a Raspberry
>> Pi or BeagleBone Black or such.  It'll be ugly because it'll likely
>> involve writing a kernel driver to get the timing right, but well...
> I have the feeling that any OS will get in the way of the proper timing 
> measurements that seem required, but I've never tried to do something like 
> that in the kernel so maybe I'm just wrong on that.

that's what I expect; but maybe if I disable interrupts from one edge to
another that interval is short enough not to interfere with overall

So it may be possible to do, but what really worries me is how do I
ensure that nothing else there interferes with it?  With the MCUs the
only outside influence is when the host can't handle the output of the
device as fast as it is generated, and with the buffering going on
within the assorted interface chips that simply shouldn't be an issue.
Once we do real-time stuff on a not-that-realtime operating system,
things do get much uglier.

So I really just want to know how far we can push the throughput as a
baseline for further work on the analog side of the generator.



Benedikt Stockebrand,                   Stepladder IT Training+Consulting
Dipl.-Inform.                           http://www.stepladder-it.com/

          Business Grade IPv6 --- Consulting, Training, Projects

BIVBlog---Benedikt's IT Video Blog: http://www.stepladder-it.com/bivblog/

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