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Subject: 
Re: controlling RCX from PC?!
Newsgroups: 
lugnet.robotics
Date: 
Wed, 27 Oct 1999 19:31:01 GMT
Original-From: 
nik heger <nik@+StopSpam+stagecast.com>
Viewed: 
735 times
  

Remember the NASA Pathfinder? Signal round-trip was about 30 minutes! Still,
they did some interesting research. Try to put more decision-making
capabilities in the RCX itself and let the PC handle its behaviour on a more
global level.
What I'm trying to say is: Let the RCX do the driving and the PC do the
navigating. The 'driver' can decide when to stop for an obstacle. It can
also ask the navigator which way to go at an intersection. This way there
will be a lot less messaging going on, you can speed up your robot and still
avoid accidents. You will probably have to redesign your software to achieve
this.

thanks matthew and arjen!

that's exactly what i am going to do.

what i did not realize at first is that 2400 baud actually *is* way
too slow, as 2400 bits/s is only 240 bytes per second. a message has
a length of around 10 bytes (depending on the op code) and the
response is at least 5 bytes greater than that, so it takes about 25
bytes to send a command and receive a response. that is about 9
communications attempts per second in the best case (no lost packets,
no switch time for send/receive). 3 of these is requesting the status
of the sensors. too slow for real time control (at least the type i
am doing).

thanks again for your help.

nik

ps: NASA probably had more resources than i do. while i don't know
their numbers, i am sure it was more than one person and more than 2
days :-)
______________________________________________________________________
nikolaus heger
nik@stagecast.com PGP fingerprint:
650.354.0735     970A 0D39 41BD A660 AACB  674B 747A
79C0 55B8 8F9D
______________________________________________________________________



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