12-03-2003, 08:35 AM
Has anyone here done anything as far as writing a QBasic program that can communicate with/program the RCX? I'm trying to learn how to do stuff like that, and it would be nice to have somewhere to start....
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12-03-2003, 08:35 AM
12-03-2003, 08:48 AM
RCX?
12-03-2003, 09:00 AM
12-03-2003, 09:07 AM
qbasic to rcx? the closest ive heard of is 'not quite c' (NQC), do a google
12-03-2003, 09:18 PM
I know it's been done before... this book had an appendix, and a QBasic -> RCX program was mentioned, but the URL was 404.
I'll try googling it....
I'll try googling it....
12-04-2003, 04:09 AM
depends on how its hooked up. If it hooks up to the parallel port, qb can do that easily. USB ->, well, different story.
12-04-2003, 05:04 AM
Serial port, and there's a little more to it than that.
12-04-2003, 07:31 AM
Code:
#!/usr/bin/perl -w
#
# $Id: talkrcx.txt,v 1.3 1998/10/08 03:44:26 paulh Exp $
#
# Talk to your RCX, in hex.
# Written by Paul Haas, http://hamjudo.com.
# Most of what I know about the RCX communication protocol came from
# came from reading Kekoa Proudfoot's webpage,
# http://graphics.stanford.edu/~kekoa/rcx/index.html
#
# Most of what the rest of what I know about the RCX came from the
# Lego Robotics web page http://www.crynwr.com/lego-robotics
# maintained by Russell Nelson.
#
# You must read those pages to understand this program.
#
# This is almost the very first release, 0.2. It's got a bunch of limitations.
# It is not tolerant of communication errors.
#
# Set the serial port to match where you plugged in your IR tower.
# (This should be a command line parameter or something.)
$port = "/dev/cua1";
open("portfh","+<$port") || die "opening $port for input: $!";
#
# http://www.crynwr.com/lego-robotics says:
# The IR protocol associated with sending a "message" to the RCX is
# pretty simple. Bit encoding is 2400 baud, NRZ, 1 start, 8 data, odd
# parity, 1 stop bit.
# Make it so.
system("stty 2400 -echo parodd parenb cs8 -cstopb raw < $port");
# All messages start the same way.
$messageHeader = hex2str("55 ff 00");
#
# Every other message has the sequence number bit set.
# This program makes the sequence bit the inverse of the bit
# from the previous message. The "1234" is just an arbitrary
# previous message.
$message = "1234";
print "talkrcx Version 0.2, using $port for the serial port.\n";
print "Type> ";
while(<>) {
$y = hex2str($_);
$message = toMsg($y,$message);
$response = str2hex (getMsg("portfh",$message));
print "In: $response\n";
print "Type> ";
}
close("portfh");
#
# If we don't like the string we get back from the RCX,
# complain about it. This could use work...
sub msgError {
local($errorstr,$message,$response) = @_;
$ostr = str2hex($message);
$istr = str2hex($response);
print STDERR "$errorstr: sent $ostr\n got $istr\n";
return '';
}
sub getMsg {
local($portfh, $outmsg) = @_;
local($inmsg,$inbuff,$rin) = ('','','');
local($sum,$sumGood) = (0,0);
#
# Send the message to the RCX.
sendMsg($portfh,$outmsg);
#
# Read it back. This reads stuff until there is no character
# for 0.3 seconds in a row. If this knew the reply length,
# it could do something smarter. As it is, sometime .3 seconds
# isn't long enough.
vec($rin,fileno("portfh"),1) = 1;
while ( select($rout=$rin, undef, undef, 0.3) ) {
$char = '';
sysread ("portfh",$char,1);
$inbuff .= $char;
}
#
# Make sure that the reply includes an accurate echo of our
# request.
if ( 0 != index($inbuff,$outmsg)){
return msgError("No echo",$outmsg,$inbuff);
}
#
# Then it should have the standard message header.
$inbuff = substr($inbuff,length($outmsg));
if ( $inbuff !~ s/^$messageHeader//s ){
return msgError("No response header",$outmsg,$inbuff);
}
#
# Now make sure each character is followed by its complement.
# Also keep track of the checksum.
while( $inbuff =~ s/^(..)//s ) {
$cpair = $1;
$oc = ord($cpair);
if ( compBad ($cpair) ) {
return msgError(sprintf("bad complement %02x",$oc),$outmsg,$inbuff);
}
$inmsg .= chr($oc);
$sumGood = $sum == $oc;
$sum = 0xff & ( $sum + $oc);
}
if ( ! $sumGood ) {
return msgError("Bad checksum",$outmsg,$inbuff);
}
$inmsg =~ s/.$//s; # Remove checksum from response
substr($inmsg,0,1) = chr(ord($inmsg) & 0xf7); # remove sequence #
return $inmsg;
}
#
# Given a pair of characters, return true if they are not a complements.
sub compBad {
local($pair) = @_;
local ($c1,$c2) = split(//,$pair);
return (ord($c1) != (0xff ^ ord($c2)) );
}
#
# send some characters.
sub sendMsg {
local($portfh, $msg) = @_;
syswrite $portfh, $msg, length($msg);
}
#
# Convert a string into hex for easier viewing by people.
sub str2hex {
local ($line) = @_;
$line =~ s/(.)/sprintf("%02x ",ord($1))/eg;
return $line;
}
#
# $string = hex2str ( $hexstring );
# Where string is of the form "xx xx xx xx" where x is 0-9a-f
# hex numbers are limited to 8 bits.
sub hex2str {
local ($l) = @_;
$l =~ s/([0-9a-f]{1,2})\s*/sprintf("%c",hex($1))/egi;
return $l;
}
#
# Take a request and make it into a happy packet.
# Note that the sequence number bit should be the opposite
# of the last packet. We use the last packet for that
# information.
# Packets start with a standard 3 byte header, the data
# and then end with a checksum. Every byte is followed
# by its complement.
sub toMsg {
local ($str,$lastMsg) = @_;
local ($msg) = "";
local ($sum, $c, $invC,$seqno);
$sum = 0; # Checksum;
$msg = $messageHeader;
$seqno = 0x08 != (0x08 & ord(substr($lastMsg,3,1)));
if ( $seqno ) {
substr($str,0,1) = chr(ord($str) | 0x08);
} else {
substr($str,0,1) = chr(ord($str) & 0xf7);
}
foreach $c ( split(//,$str) ) {
$invC = chr(0xff ^ ord($c));
$msg .= $c . $invC;
$sum += ord($c);
}
$sum &= 0xff;
$msg .= chr($sum) . chr(0xff ^ $sum);
return $msg
}Toonski might be able to help you about that code. And don't forget to follow the link Plasma gave you.
12-04-2003, 08:11 AM
SHARP-BANG! perl!!!!
12-04-2003, 08:19 AM
Not a big deal, and Toonski's known as a proficient Perl coder. (Or was that a joke? I don't remember it. 
)
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