Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!isi.edu!schur
From: schur@isi.edu (Sean Schur)
Newsgroups: comp.sys.amiga.programmer
Subject: AREXX Question: Reading ser: port
Message-ID: <17683@venera.isi.edu>
Date: 23 Apr 91 09:13:41 GMT
Reply-To: schur@venera.isi.edu (Sean Schur)
Organization: USC-Information Sciences Institute
Lines: 62

I am trying to use AREXX to control a Lyon-Lamb Minivas. This is a single
frame recorder controller for single framing images to videotape. The
MiniVas has a standard RS232 port. It accepts standard ASCII characters
for control. I have had complete success in using AREXX to control the
MiniVas. I have an AREXX script that will display a series of images
one by one on the Video Toaster and tell the MiniVas to grab the frame
once it is displayed. No problem.

Now I want to turn things around. Supposedly the MiniVas also sends
out standard ASCII characters reporting on it's current state. What I
want to be able to do is to have the MiniVas tell the AREXX script when 
it gets to a particular frame, then activate the Toaster at that point
to do a framegrab. The reason I want to do this is to be able to grab
a series of images to do animated image maps for Lightwave. So, for example
I could grab a series of 60 frames of a movie, then have those frames
play on the screen in an animation in Lightwave.

The problem I am having is how to run tests to figure out what ASCII 
characters are being sent by the MiniVas at exactly what point. For my
earlier script (to send characters TO the MiniVas) I could set up a 
simple script that would open the SER: port as a logical file, then
pull a character from the keyboard and do a "writech" to send the
character to the SER: port. Easy enough to do a loop so I could type a
"+" and it would start to play, and a "<" and it would rewind. I had
direct control over the MiniVas from the keyboard. 

I want to be able to do the same thing now, to send characters to the 
MiniVas, but I also want to be able to find out what the MiniVas is 
sending back. Optimally I would like some process watching the SER: port 
for any incoming characters while I send out characters as well. I can't 
run two separate AREXX scripts. If I have one running that has the SER:
port open and I run a second, the second one fails when it tries to
access the port.

The other option is to run one script in a loop. Allow me to send
a character to the MiniVas then look for a response, if there is none
let me send another character, etc. The problem I am having with this
(and it is probably AREXX ignorance) is that after sending a character
with "writech" I am using "readch,1" to look for a single character.
The program isn't receiving one and the script completely freezes, I can't
get out of it at all without rebooting. I am pretty sure that I need to
send a particular character first to tell the MiniVas that I want it
to start sending it's status. The documentation for the MiniVas is
pretty bad and I need to be able to try several different things before
I figure it out.

So, how do I tell AREXX to TRY to read a character, if it doesn't get
one within a specified length of time, to return control of the program
to me so I can type another character. It would also be desirable to
have the script echo the character to me immediately as opposed to 
writing it into a file to look at later.

Any suggestions and help would be appreciated.

Thanks.

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Sean Schur		    			USENET: schur@isi.edu	
Assistant Director Amiga/Media Lab		Compuserve: 70731,1102	
Character Animation Department			Plink: OSS259	
California Institute of the Arts
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