4x20 huge LCD problem

Scarecrow

hi guys,

i just bought a 4x20 lcd and i made it work but i get some very strange results and ive tried everything and i think im going to hang myself now...hehe BUT before i do i tought that maybe you guys had the same problem so maybe theres hope in my life so here it is:

ive programed the lcd to display a character and display in the debug terminal the adress where that character is

the problem comes when in the first line at the 13·position it has a duplicate in line 2 at the first position, and then when line 1 is finished that duplicate(which is now in pos 9·of line 2)continues to finish line 2

same for line 3 and 4

i dont know what could be the problem and i really would like to make this work, ive read other posts with the same problem but no solution, thanks in advance =P

Jon Williams

There are a lot of cheap displays out there that don't use "standard mapping" of display addresses (DDRAM). Before you hang yourself, write a simple program that slowly walks through the DDRAM addresses and prints a "*" or other character; use DEBUGIN to control the loop so that you can monitor the addresses. It will take a few minutes, but you may discover the logic of the display mapping.

One must assume you think that your code is at no fault here since you declined to post it....

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Jon Williams
Applications Engineer, Parallax

Yanroy

Without knowing what kind of LCD you have, I could be way off base with this suggestion, but it seems to me that you could be experiencing a problem related to initialization.· Parallel LCD's with the HD44780 (or equivalent) controller need to be initialized with their size.· If you set the size wrong (say, 2x12, if that's even a valid size), it might cause this weird ghosting/wrapping you're experiencing.· I got a problem where it wouldn't let me write to the end of a line on my LCD, which is sorta similar to your problem.· Just a guess...

Philip Gamblin

I just went through the headache your are experiencing. I ended up doing exactly what Jon has described and finally managed to get a functional but not perfect display. If you want to solve this problem quickly, Purchase a 2 X 20 SERIAL display from Parallax. Then you have a known hardware quantity( which is a good chunk of the problem you now have) , and plenty of ready written software. I had mine working about 20 min after getting it to the bench. Much better than the 6 or 8 hours of hardship and frustration trying to get my $4.95 " bargain " display to work. Just my humble opinion.

Chris Savage

Philip,

·· While I am inclined to agree with you for many reasons, there are those that will buy the bargain or surplus LCDs, and for those circumstances Jon has a good point.· Assuming the connections are the same as other LCDs (Most are) and at least a Hitachi-Comaptible controller, then you can at least map the display by slowly printing to all the addresses (Displaying the address in DEBUG) and determine mapping.· And of course, it always helps to obtain the datasheet for any LCD.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Scarecrow

well this is a blue backlit lcd with serial,4 and 8 bit interface posibilities from "electronic assembly" the controller is a KS0073 wich is 100% hitachi HD44780 compatible and it seems like a extremely nice product: its small, ready to mount over a circuit, good contrast......BUT as you see...theres a problem.....hehehehe i have already the adresses of the lines, i agree that this might be an initialization problem but i have absolutely no clue =S ill keep trying to find asolution but ill loose my sanity hehehe, also im sure its not a code error because even if i use it to write only the first line the problem appears, i have seen the same problem in other forums but no solution =(

Post Edited (Scarecrow) : 7/21/2005 3:40:29 PM GMT

Buck Rogers

Hello from Buck Rogers
Folks in my supply space are four LCD displays. One is a large format a 4x16 one from Optrex, the others are all 2x16 devices. One is a new one, the others are surplus.

The heck of it is that they are all using the Hitachi controller, and have the same pinouts. Also the same "instruction sequences". All are parallel controlled by the way.

So unless we see either the code, or screenshots of the device at work, we can't assume anything.

Personal for both Chris, and Jon, your both right.

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Buck Rogers

www.gregg.levine.name

GRC

Hi Scarecrow
From experience, usally the pinout connections cause the most trouble.
Find the data sheet and double check the connections, then check them
again.

Good Luck
Gordon

Scarecrow

ok, ill try to be as detailed as i can, i took some pictures of the lcd in action and i posted the bs2 code for the adress test and normal characters test(its john williams code, thanks for that :P), i hope it helps =S, the address when the characters clone for line 1 starts at address $8C maybe that helps........from the internet i got that line1 address was $00, line2 $14, line3 $40, and line4 $54......

Chris Savage

·· Just out of curiosity, when you manually set the address to a specific line as per Hitachi compatible displays, where does the character land?

addr = $80 + $00· (Line 1 position 0)
addr = $80 + $40· (Line 2 position 0)
addr = $80 + $20· (Line 3 position 0)
addr = $80 + $60· (Line 4 position 0)

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Scarecrow

if i do "01234567890123456789" to these addresses:
addr = $80 + $00 (Line 1 position 0)
addr = $80 + $40 (Line 2 position 0)
then you get the result you see in lcdtest.bmp

if i do the whole 4, the same problem in line 1 and line 3 copying to line 2 and 4 after character 13

Post Edited (Scarecrow) : 7/22/2005 3:11:16 PM GMT

Chris Savage

Wow,

·· That is weird.· I think I finally grasp what you're saying is happening.· After character 13 you're saying data prints to two locations at the same time?

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Chris Savage
Parallax Tech Support
csavage@parallax.com

OakGraphics

Have you tried removing the lcd from your circuit and attaching it to your computer in parallal mode - and use a program like lcdc to generate a test display? I am trying to suggest a method to determine if the circuit you built is mis-wired versus the lcd actually having a hardware problem.

Nice display actually. Where did you get it? (I might not want to buy one until your problem is solved, but it's still very small and cute!)

Scarecrow

YES! CHRIS!, im going to try to use it in 8 bit mode to see what happens and maybe ill try serial mode but i have no idea how to do it serial mode, i got it from www.distrelec.com·its an european electronics dealer...=P

Post Edited (Scarecrow) : 7/22/2005 6:45:07 PM GMT

Scarecrow

hehe, i dont have a parallel port in my pc and i cant get the lcd to work in 8 bit mode, could you guys spare me some code to control it 8 bit mode? =S sorry....

Scarecrow

i think i got kinda of an idea of the problem, in 4x20 lcds theres an extension register or something like that and im failing to initialize it in 4 line mode anyways its a very vague idea i dont understand th datasheet if you guys wanna help here it is(i would really appretiate it, im giving up on the lcd =(...)

Scarecrow

OK I GOT THE SOLUTION!!! (Weeeeehhaaaa!!!), it was all in the initialization procedure, you have to enter extended function set, then say 4 lines, then exit, then do the other normal initializations, like this:

char = %00101100 'enter extended function set
GOSUB LCDcmd
char = %00001001 '4 lines
GOSUB LCDcmd
char = %00101000 'exit extended function set
GOSUB LCDcmd
char = %00001100 ' display on, cursor off, blink off
GOSUB LCDcmd
char = %00000110 ' inc crsr, no disp shift
GOSUB LCDcmd

pBASIC

Here is some help in serial if you do use serial
==================================================================================================
PAUSE 4000························· 'Pause (4sec) Wait for LCD Bootup to Clear
SEROUT 9,BAUD,[noparse][[/noparse]003]················ 'Hide display
SEROUT 9,BAUD,[noparse][[/noparse]014,100]············ 'Turn Backlight to 100% (On)
SEROUT 9,BAUD,[noparse][[/noparse]020]················ 'Turn Scroll Off
SEROUT 9,BAUD,[noparse][[/noparse]024]················ 'Turn Wrap Off
SEROUT 9,BAUD,[noparse][[/noparse]004]················ 'Turn Cursor Off
SEROUT 9,BAUD,[noparse][[/noparse]CLR]················ 'Clear Screen
SEROUT 9,BAUD,[noparse][[/noparse]LINE1]·············· 'Goto Home Position
SEROUT 9,BAUD,[noparse][[/noparse]"Hello World!"]····· 'Display Text
SEROUT 9,BAUD,[noparse][[/noparse]017,000,001]········ 'Position Cursor at Col 1 of Line 2 on LCD
SEROUT 9,BAUD,[noparse][[/noparse]"Text Sent by BS2"]· 'Display Text
PAUSE 4000························· 'Pause
SEROUT 9,BAUD,[noparse][[/noparse]CLR]················ 'Clear Screen
·

Short

Try this sample code its for non LCD support, It should work for you.




'{$STAMP BS2}
'{$PORT COM2} ' Dont forget here



E CON 7 ' CHANGE HERE for YOUR pins to LCD
RS CON 8

Char VAR BYTE
DA VAR BYTE

MAIN:
pause 1000
GOSUB LCD_ini

DIS:
Char = 12
GOSUB LCDcmd
Char = 133 ' CHANGE VALUE HERE FOR diferent CURSER SPACES
GOSUB LCDcmd
Char = 69 ' VALUE for E
GOSUB LCDda
Char = 77 ' VALUE for M
GOSUB LCDda
Char = 73 ' VALUE for I
GOSUB LCDda
Char = 84 ' VALUE for T
GOSUB LCDda

STOP



LCD_ini:
LOW 9
'PAUSE 1000
Char = 48 ' 8-bit mode
GOSUB LCDcmd
PULSOUT E, 1
PAUSE 10
Char = 48 ' 8-bit mode
GOSUB LCDcmd
PULSOUT E, 1
PAUSE 1
Char = 48 ' 8-bit mode
GOSUB LCDcmd
PULSOUT E, 1
PAUSE 1

PAUSE 5
PULSOUT E, 1
PULSOUT E, 1
Char = 32 ' 4-bit mode
GOSUB LCDcmd
PULSOUT E, 1
Char = 40 ' Set for 2 line operation
GOSUB LCDcmd
Char = 12 ' Shift cursor right
GOSUB LCDcmd
Char = 6 ' Increment DDRAM after write
GOSUB LCDcmd
Char = 1 ' Clear LCD screen
GOSUB LCDcmd
Char = 4
GOSUB LCDcmd
RETURN



LCDcmd:
LOW RS



LCDwr:
DA = Char.HIGHNIB
GOSUB CONV
PULSOUT E, 1
DA = Char.LOWNIB
GOSUB CONV
PULSOUT E, 1
HIGH RS
RETURN


LCDda:
HIGH RS


LCDwrD:
DA = Char.HIGHNIB
GOSUB CONV
PULSOUT E, 1
DA = Char.LOWNIB
GOSUB CONV
PULSOUT E, 1
LOW RS
RETURN


CONV:
OUTPUT 3
OUT3 = DA.BIT3 ' CHANGE HERE for the pins you have connected to LCD 4 bit mode
OUTPUT 4
OUT4 = DA.BIT2
OUTPUT 5
OUT5 = DA.BIT1
OUTPUT 6
OUT6 = DA.BIT0
RETURN

Short

Dont forget to TAKE LOW 9 OUT of program!

OakGraphics

scarecrow - I was flipping through the pbasic manual today and noted most lcds do take a bit of time to initialize. You might need some wait statements in there to give it a break. It suggested at least 700ms then sending 3 sets of wake commands. Also - some commands need a delay before doing anything else. :-/

Either way I am glad you got it working! It's a very cute display to say the least!

OakGraphics

Speaking on serial control of these lcds- I am starting to see futaba and the like VFD that can do serial control. Has anybody tried them yet?
I would think I would prefer serial any day. I see Pbasic having some code on this in this thread. Pbasic - what model(s) did you use with that?
Just trying to find a 4x20 lcd/vfd that is small and can be controlled serial wise without tossing out more then 30$ for the deal.

Chris Savage

OakGraphics said...
scarecrow - I was flipping through the pbasic manual today and noted most lcds do take a bit of time to initialize. You might need some wait statements in there to give it a break. It suggested at least 700ms then sending 3 sets of wake commands. Also - some commands need a delay before doing anything else. :-/
Either way I am glad you got it working! It's a very cute display to say the least!

·· Here's a little bit of information that can help you avoid putting pauses in your code for LCDs when using them in Parallel mode...The Hitachi/Compatible displays have what's called a BUSY flag that is set when the display is ready for a new character or command.· This is easily read by the BASIC Stamp or SX, and allows you to start sending data as soon as the LCD is ready.

·· Basically you read in the command register (Which will read in the current address pointer) and check the state of BIT7.· If BIT7 is set, you re-read the register until it's cleared then send your next character/command.· This is more useful to the SX, but the faster BASIC Stamps, such as the BS2px24 could find themselves wasting time pausing when it might be quicker to simply check the busy flag at the entry point into your LCD write routine.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

pBASIC

I know this is kind of dumb but I think that program I found was in the help file for the basic stamp editor search in it for SEROUT.

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