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 Robotics / RCX / NQC / 1139
1138  |  1140
Subject: 
Re: NQC vs Spirit communication speed
Newsgroups: 
lugnet.robotics.rcx.nqc
Date: 
Fri, 11 May 2001 17:51:40 GMT
Viewed: 
2173 times
  
In article <dbaum-295BE9.11412611052001@lugnet.com>, Dave Baum
<dbaum@spambgoneenteract.com> wrote:


* Enabling predictive replies (set fPredictive field true) can help a
lot since in many cases the link is able to tell when a complete reply
is received without waiting for the full timeout.  Actually, one of my
gripes with the RCX packet format is that you can't always tell the
length of a packet without also interpreting the contents of the packet.
This makes it difficult to partition the delivery of packets from the
use of packets.  So not all of the packet times will take advantage of
predictive replies.  I think I included data for the ones NQC commonly
uses, but probably not for the stuff you are doing.  Look at the
PredictReplyLength() method - it needs to return the expected number of
bytes for a given bytecode.  The default is 1000, which really just
means keep reading until the timeout.


I looked into this a bit more and the poll bytecode (0x12) didn't have a
case in the PredictReplyLength() switch.  If you add...


      case 0x12:  // poll
         return 2;

then poll will be a lot faster.  If you run into other bytecodes that
you use a lot, adding them into the switch statement will help.  At some
point I'll go through and put them all in (or code them as a table
instead of a switch).

Dave Baum

--
reply to: dbaum at enteract dot com



Message is in Reply To:
  Re: NQC vs Spirit communication speed
 
The retry timing for RCX_Link uses a dynamic backoff, which is a good general purpose solution if you're going to be sending lots of packets (like a typical NQC download) and the latency through the serial driver is unknown and/or unpredictable (...) (24 years ago, 11-May-01, to lugnet.robotics.rcx.nqc)

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