Subject:
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Re: NRLink reading RCX response w/ RobotC
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Newsgroups:
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lugnet.robotics.nxt
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Date:
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Fri, 3 Aug 2007 01:02:09 GMT
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Viewed:
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20471 times
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> The best way to understand the format of RCX IR messages is to
> download the RCX SDK from the LEGO web site and read the documentation
> in it. Here's a few pointers on the basics.
>
> Every message is prefixed by optional header bytes which begin with
> 00, FF, or 55. There can be an unlimited number of header bytes.
> Normally there are 3 and they are 55, FF, 00 but if a byte is dropped,
> etc you can get a different quantity. Or you can customize the RCX
> firmware -- it's a simple byte-value parameter -- to set the number of
> prefix bytes.
I downloaded the SDK from http://mindstorms.lego.com/sdk2point5/ but can't find
any reference to the message format. Perhaps this is the wrong SDK? I've
looked in all the doc .pdf files and skimmed everything else. I sure am having
a hard time locating things.
> Every message is prefixed by optional header bytes which begin with
> 00, FF, or 55. There can be an unlimited number of header bytes.
> Normally there are 3 and they are 55, FF, 00 but if a byte is dropped,
> etc you can get a different quantity. Or you can customize the RCX
> firmware -- it's a simple byte-value parameter -- to set the number of
> prefix bytes.
>
> So message should begin with the first non-zero prefix byte.
So what happens if the message actually begins with a header byte or a zero, say
FF or 00? It seems to be very difficult to determine exactly where the prefix
header ends.
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Message has 1 Reply:
 | | RE: NRLink reading RCX response w/ RobotC
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| (...) Look at the file "RCX2 LASM Byte Codes" for a description of each of the available opcodes. Read (URL) coupled with the contents of my previous email. (...) No valid message starts with with 'opcode' byte of '00' or 'FF'. [Check out the above (...) (17 years ago, 3-Aug-07, to lugnet.robotics.nxt)
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Message is in Reply To:
| | RE: NRLink reading RCX response w/ RobotC
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| (...) I couldn't find it either, but its out there somewhere. (...) Agreed. It started as a internal debugging tool and was left visible for the small handful of power users who write their own I2C device drivers. (...) Agreed. I went back and (...) (17 years ago, 2-Aug-07, to lugnet.robotics.nxt)
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