Newsgroups: comp.robotics
Path: brunix!sgiblab!sgigate.sgi.com!olivea!news.bu.edu!att!cbnews!gwk
From: gwk@cbnews.cb.att.com (george.w.kinder)
Subject: Re: 6.270 board LCD problem
Organization: AT&T
Date: Mon, 13 Dec 1993 17:47:25 GMT
Message-ID: <CHzIr7.BMx@cbnews.cb.att.com>
References: <2eddk7$s5o@mojo.eng.umd.edu>
Lines: 31

From article <2eddk7$s5o@mojo.eng.umd.edu>, by farris@eng.umd.edu (Timoth F Kadom):
> I am relatively clueless about LCD modules, and probably have made an
> error in purchasing mine.  I have an Optrex 16x2 LCD, which can be driven
> by 5V.  I thought this would be enough, since I am building two boards
> I bought two of these.  My friend already has his 6.270 board assembled and
> working (though he uses a different make LCD).  When I plug my LCD into his
> board I can not see any text, though it seems that the board is still
> working properly underneath (ie programs still run, I just don't see
> any output).  Can someone tell me what the problem might be, if there is
> a fix, or if I need to get new LCD modules?  The chips used by the LCD's
> are identical, but the layouts are slightly different.  my LCD was much
> cheaper, but seems to include all the "normal" features...
> 
> 			-confused,
> 				Tim
Tim,
I also had trouble getting a 16x2 LCD working where a 16x1 had been before.
(not on 6.27 board...but maybe the same problem)
There is an LCD bias pin that is normally connected to a pot between
gnd and +5. 
My 16x2 required a bias outside that range. I can't recall off-hand 
whether it was above +5 or below ground, but the LCD was not usable 
until I used another supply for that bias. 
Check the data sheet carefully for the specified range.
YMMV
gwk
-- 
*  I don't speak for AT&T.       *    George Kinder   gwk@cblpe.ATT.COM  *
*  AT&T doesn't speak for me.    *    AT&T Bell Laboratories (I think)   *
*  We both like it this way.     *    Columbus, Ohio       614-860-2238  *

