DPRG mailing list archives: [DPRG] Processing unit for mobile robot

Wed Apr 23 22:54:50 CDT 2008

ed at okerson.com said: Wednesday, April 23, 2008 5:06 PM
> http://rt.wiki.kernel.org/index.php/Main_Page

Thanks for the link, I did some reading/scanning. It is
difficult to get far thought. I don't know if you can appreciate
it or not, but to an outsider, you can't read a single page
without running into a dozen acronyms or terse references that
can't be understood. 

> 10-30us scheduler and interrupt latencies; 

So my interpretation is that a PC is just now approaching
latencies of a 2MHz 68HC11, which had a longest latency of a
divide instruction of 41 cycles or 21uS plus a call time of
something like... Was it 11 cycles? 

Or am I not understanding what this means on a PC? Now
admittedly, the HC11 couldn't do as much once it got to a
routine. 1000x Clearly. But I'm thinking this is a measure of
how long a response to a real time request runs?

> After all, humans are inherently non-realtime, but we do 
> much more than just move around.

I don't know if I agree. Humans have latencies in sub-second
range, and we largely consider that normal response times. We
consider quadraplegics, unable to feed themselves or move more
than their eyes as severly disabled. While everyone is amazed at
Stephen Hawkings mind, his situation is not to be envied. So I
think what we do is still motion related.

Also if you listen to our language, and examine how we put
things, I'd say our very consciousness is based on motion.
Example phrases: "Run that by me." "Hold that thought." "I'm
trying to grasp the concept." "You've moved me." "I'm not
following you." "Please explain your thought path." "How did you
arrive there?" Nothing moves in the brain, but all these phrases
are motion based descriptions of mental internals.

> What I see as so desireable is to not have to create 
> everything from scratch myself.  By using an Operating 
> System, many people can work to the same API and build parts 
> of the system.  But by using an open source operating system, 
> you still get all the source code so you can tweak it if you 
> so desire.

Okay, I hear that you want to make use of others code. I know
there are some vision programs. I know you can make use of
network codes. Believe me I'm not trying to be facetious, but,
does useful code for robots exist? Is there OpenPID? OpenNav
OpenSteering?

Maybe there are. I tried Open GPS and got several hits. Not so
sure the others worked. .PID and .NAV are apparently file names,
and there are lots of articles on how to "open" those files.

Maybe I should look at LEAF some more. I have largely rejected
the Open software movement for reasons I won't dive into right
here.

> I choose Linux because of consistency.  I can use the same 
> tools regardless of what platform I am developing for, and my 
> code compiles and runs on several platforms with consistent 
> interfaces and API's.  And this is all possible without 
> spending large sums on development tools.

Okay.

The same is true for me and Forth, except I can work on even
smaller platforms. So I can see that side of the argument.

> Choice of Operating Systems, be it Linux, Windows, Mac, etc, 
> or none at all, is a personal choice, and discussions about 
> it tend to degrade into flame wars, so let's keep this one
calm.

Oh, I agree, completely. The subject to me of interest is: OS -
why? And not OS - which one?

Randy