Subject:
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Interactive communication with the RCX
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Wed, 24 Apr 2002 07:19:33 GMT
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Viewed:
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2977 times
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I have recently discussed with Kekoa an interesting issue that apparently
received scarce attention in the past.
I'm trying to have interactive communication between the
computer and the RCX through IR connected to an USB port:
sendind commands from the computer to the RCX,
while waiting for asynchronous event messages sent back from the RCX.
I'm using the LEGO firmware with the LASM assembly, but the problem
appears with any other substitute.
Each one of the two functions separate operates properly: I can reach a rate of
1/50ms for messages from the RCX and 1/100ms for commands from the computer
(send and receive the answer), however, when the two operations are
intermixed sometime the messages are corrupted.
Kekoa points out that the problem doesn't depend on the software but it is
intrinsic with the IR communication media that in practice isn't full duplex.
What is needed is to implement a kind of collision detection protocol
if one want to use an asynchronous communication mode, or polling event from
the computer (very bad solution), or continuous synchonization messages sent
from te computer to marshall the communication.
Someone can give me a suggestion? And particularly help me in implementing
a kind of protocol at the very button level of the brick?
Giuseppe Menga
menga@polito.it
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Message has 1 Reply:
 | | Re: Interactive communication with the RCX
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| I don't think collision detection will be possible since the hardware/firmware does a checksum (at least in lego firmware), and no message is provided to the VM software (LASM), this prevents ACK/NAK protocols working. The Message() function does (...) (23 years ago, 24-Apr-02, to lugnet.robotics.rcx)
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