View Full Version : LCD Trouble [solved]

01-11-2006, 12:18 PM
Hello. I am sorry to bring a previous post back up from the archives, but I am having the exact same problem and there was no reply to the post posted on 6/3/2003 at 6:17 AM. Or at least the replies are not in the archive. Here is what the post contained:
Archiver said...
Hello, I was wondering if anyone could help?

I have just got my hands on the blue and white LCD 20 X 4 from
Parallax. It is the LK204-25-WB.

I hooked it up to my serial port and modified a power connector to
the correct pin out and with 5V. I connected the ground of the power
supply to the ground of the serial cable. The screen turns on and I
get the flashing cursor in the top left of the screen. Perfect.
Looks really good by the way!

The problem comes when I try to send data to it. I tried the Matrix
Orbital Tester Online software that came with it.

When I write the word "test" and send it to the module the result on
the screen is "QSt||"

I have tried it on the Com 1 and Com 2 port and tried 2 different
straight through cables. The port setting for both is 19200 baud rate
and no flow control. I have tried it with software flow control as
well, with the same result. If I try hardware flow control
everything slows down on my PC.

I have checked the jumper settings on the board and have also tried
everything at 9600 baud with exactly the same result.

I then tried to just type in the box at the top of the Matrix Orbital
Tester Online which I assume gives a real time display on the LCD of
whatever you type. The results were as follows:

Typed: Output:

Q w
7 d
Z )
1 g
G •

I have also found that the following commands have the following

8 Clear Screen
x Backspace
X Line Feed.

One more thing is that when typing data to the LCD it displays it
first on line 1 then line 3 then 2 and then 4.

Is this correct?

The backspace and line feed work as expected (Lines 1,2,3 then 4) but
every other key will follow the 1,3,2,4 sequence.

It looks to me that the data is being corrupted or mis-interpreted in
some way.

I have also tried the a reset procedure but this has made no

I have also tried to control it via Hyper term but every time I tried
to connect, Hyper term just crashed as though there was a COMMS
error. I tried to connect another serial device to the serial port
and that worked fine.

I have got a sneaky feeling that I have overlooked something silly
but at 3:30 this morning the coffee and curry powered brain finally
gave up!

Can anyone help? Is it something I am doing wrong or could it be
that there is a fault with the LCD?



Thank you very much,

The link btw is http://forums.parallax.com/showthread.php?p=502208


Post Edited (Mag748) : 1/12/2006 4:30:48 PM GMT

Chris Savage
01-11-2006, 12:21 PM
You have given no information on how you are connecting this display?∑ Are you connected to a BASIC Stamp or a PC?∑ The member you refer to connected the LCD to his PC.∑ If it came from us you cannot do that directly.∑ The units we carry are for TTL Serial Only.∑ So that was his/her problem.∑ It is always wise to provide details when requesting help to minimize the numbers of questions we have to ask to help you.

Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

01-11-2006, 12:31 PM
Ohh. Im sorry about that. I know it doesnt work when connected to the badic stamp, but I will provide details about how I connected it, and the program I used later today. Thanks alot.

I am an idiot.



01-12-2006, 05:48 AM
OK. Hello again. Let me try again.
I have hooked up my LK204-25-WB-C74 just like it said in the 30058Errata.pdf and connected the Rx pin to pin1 on my Basic Stamp II. When I turn the BOE on and the display comes on, it just displays a full screen of the custom characters that used to make up the little M\O icon thing that it would display on start up. It used to display "Matrix Orbital / LK20425-WB-C74" Now its just gibberish. Anyway, so then I tried running the 'SERIN-OUT_SENDER.bs2' program that is in the BS2 folder of sample programs since that seemed like it was the closest thing to send stuff to LCDs. The program was simply this

SEROUT∑ 1,∑ 16468,∑ ["HELLO!"]∑∑∑∑∑ ' Send the greeting
PAUSE∑∑∑ 2500

That used to just create many instances of one character. That character was again one of the custom characters stored on the LCD display.

Then I changed the baud to 19200 since the jumpers one the back of the LCD were set the that (out in in out)

That didn’t change anything.

Now I can’t get the display to work at all. When I run the same program, the characters do not change. The screen just remains all jumbled up. And when I turn off and then turn the display back on, it is still jumbled (doesn't display version number anymore.)

I hope this is enough information to help you help me.
Thank you very much.


PJ Allen
01-12-2006, 10:10 AM
What voltage were/are you running the LCD on/with?

Like this ? --


Post Edited (PJ Allen) : 1/12/2006 3:20:56 AM GMT

01-12-2006, 10:52 AM
Yes, thats exactly how it is set up. The +5v pin is connected to Vdd and the GND pin to Vss. And the jumpers are the same as well.


Chris Savage
01-12-2006, 12:27 PM
Which Stamp Module are you using?∑ What baud rate parameter did you use for 19200?

Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

01-12-2006, 10:21 PM
A Basic Stamp II. I used 19200. Which, ah, thats wrong. I need to do some conversion first. Would the correct Baudmode number be 16416 ?
That would be
∑∑∑∑32∑∑∑'INT(1,000,000 / 19200) – 20
+16384∑∑ 'Inverted

Ok, I tried that and it made some progress. Noe when the BS2 sends ["HELLO!"] the LCD displays "]∑ Xo" thats 'right bracket, space, space, capital X, lowercase O'

Ohh, it works perfectly now, I∑just used∑32. And sent TRUE(noninverted) polarity.
Thats amazing.



PJ Allen
01-13-2006, 12:36 AM
I was going to ask you that when I posted the picture, your programming showed 19200, but your mentioned changing to 9600...

You know, the numbers for baud, &c. are there in SERIN/SEROUT in the HELP

Tom-Matrix Orbital
01-14-2006, 05:12 AM
Now that you got your Basic Stamp working with the Matrix Orbital display, you can also checkout some application notes at www.matrixorbital.ca/appnotes/basic_stamp/ (http://www.matrixorbital.ca/appnotes/basic_stamp/)