Subject:
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decoding a message sent by an RCX
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Fri, 3 Sep 1999 15:42:20 GMT
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Viewed:
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1948 times
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hiya,
I have been working on an idea to extend the number and type of devices that
the RCX can control. I started with the idea of encoding serial data on one of
the motor lines and decoding that in a PIC to do <stuff>. However, because
working at the bit level in NQC is not possible it would mean that every
message would have to be built at compile time, ick. Therefore, I have decided
that receiving a message over the IR from the RCX would be far more practical
from the RCX's point of view. However I have a couple of questions for those
that know:
1. The crynwr page states that the serial format is :
NRZ, 1 start, 8 data, odd parity, 1 stop bit
I'm not used to seeing 8 bits with a parity bit, as a sanity check does this
mean that each byte is 11 bits (1 start, 8 data, 1 parity, 1 stop) - OR am I
misunderstanding this somehow. Since the RCX can send 0-255 as messages, I
THINK that I'm correct. Can someone set me straight on this?
So, which would it be? It is convenient that its using '0'= modulation and
'1'= modulation because in that way the usual IR detector module will give
"non-inverted" data straight off.
Once I successfully get the communication working, I will then need to decide
what to _do_ with the information. Run servos, run DC motors, read sensors,
whatever. Since the PIC will talk back to the RCX via the same mechanism,
anything will be possible. This may be a way to give the RCX a compass reading
ability finally!
Any other suggestions?
DLC
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Message has 3 Replies:
 | | Re: decoding a message sent by an RCX
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| (...) Yes, you are correct - 11 bits total per byte. And yes, this is very non-standard. I believe the signal is inverted - meaning that IR light is present for "0" bits, and no light for "1" bits. But I'm going from memory here and haven't looked (...) (25 years ago, 4-Sep-99, to lugnet.robotics.rcx.nqc)
| | | Re: decoding a message sent by an RCX
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| Woaw ! This could be great to have a full featured rcx expansion board... It should however be not too expensive, and in my opinion very basic to allow anything to be made. A "simple" (hehe :-) 8 bit Input / Output expander would be very, very nice. (...) (25 years ago, 4-Sep-99, to lugnet.robotics.rcx.nqc)
| | | Re: decoding a message sent by an RCX
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| (...) [...] I think something like this was already made by LEGO itself in the lab while creating the RCX/CyberMaster software. I say this because they seem to have forgot to remove the CABLE mode of transmission from the Spirit.ocx when deploying (...) (25 years ago, 4-Sep-99, to lugnet.robotics.rcx.nqc)
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