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PICList Thread
'[EE]: LCDs'
2001\01\05@220552 by Jinx

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I'm testing a bunch of reclaimed LCD screens of indeterminate
origin, 16 x1, 20 x 2, 32 x 4 etc. Going well until I went over the
handlebars when a 16 x 1 wouldn't display its full 16 characters.
It has a single 44780, and there doesn't appear to be a second
chip under the glass

Whilst tinkering (and making the odd error) with the s/w to try and
get something out of this display, I did get chars to appear in the
second 8 positions, but don't know if this was accidental and not
repeatable under controlled conditions

What I think I've understood from the Hitachi manual is

a) a 44780 can display only 8 chars of its own, and can store 80
b) it can drive 44100's, each of which can also display 8 chars

Can someone please confirm this that so I don't waste any more
time trying to get 16 chars out of an 8 char display. Or is there a
way to get twice the performance out of a 44780 ? Getting the
second 8 to light up accidentally (?) has got me intrigued

TIA

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2001\01\05@221431 by myke predko

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Hiya,

It's working fine and I think you've doped out what is happening.  Most 16x1
displays are actually 8x2 displays with the lower line concatenated onto the
first.  To jump to the 9th character, send a 0x0C0 instruction to the LCD to
move the cursor to the first character of the second line.

Good luck!

myke
{Original Message removed}

2001\01\05@233039 by ken

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TIA,
Sounds like they're working to me.
If you need them I've got several data sheets that explain the
operation of the 44780. I'll email them to you if you don't all ready
have them, let me know.
Ken

{Quote hidden}

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2001\01\06@003635 by Graeme Zimmer

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Hi all,

Am just about to lay out a PCB which people will  inevitably use to connect
to suplus LCDs.

see  http://www.users.bigpond.com/gzimmer/

Am collecting any and various LCD pin-out information...

would appreciate very much any details anyone has to hand..

thanks .............. Zim

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2001\01\06@005419 by Alejandro

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Hi, Jinx!

Well, about six months ago, I have used a chinese "unknown brand" LCD
of 16 chars for 1 line.
I was surprised because the first 8 characters are in "line 1" position
and the remaining 8 in the "line 2".
Yes, the LCD has only 1 line, but, who knows why, its characters are
organized
like 2 lines by 8 characters.

If one needs to write characters in the 8 remaining positions, you need
to send a command "SET DDRAM ADDRESS" in order to point to the
"second" ;-) line.

Maybe the code that I have dropped to PICLIST might help you
to deal with this kind of display. The code uses this display
and the name of the message is something like "PIC16F84 + LCD + RS232".
I posted it in august (or september, I dont remember). The attach
is a zip file that contains a .ASM . Two versions are posted, one
in spanish and other in english.

The code works very well and performs a simple terminal with a PIC16F84
plus 4 x 4 matrix keyboard and full duplex 1200 bauds RS232 and,
of course, a 16 char by 1 line LCD (4 bits interfaced).

I think that this may be help.
Cheers! :)


{Original Message removed}

2001\01\06@052308 by Oliver Broad

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IMO it's got to be to cut costs.

I believe it cuts down on the number of extender chips needed for a given
display size.

Oliver.
{Original Message removed}

2001\01\06@075935 by Jinx

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From: Alejandro <EraseMEalejolspam_OUTspamTakeThisOuTADINET.COM.UY>

> If one needs to write characters in the 8 remaining positions, you
> need to send a command "SET DDRAM ADDRESS" in order to
> point to the "second" ;-) line.
>
> Maybe the code that I have dropped to PICLIST might help you
> to deal with this kind of display.

Thanks, I've got a copy of that file. I've used 16x1 LCDs in the past
without problems, and now that I look at some of them I find they
have a 44780 and at least one 44100. This is the first one I'd got
that had just a 44780 and it caught me off balance. I'd tried second
line addresses but never did manage to get the second 8 chars
going on purpose. The Hitachi chip manual doesn't say explicitly
that a 44780 can drive only 8 chars, you kinda have to work it out by
flipping back and forth between the addressing examples. Getting
the second 8 lit up by some accident threw me

I'll have another look at your 4-bit s/w when I get around to the 4-bit
screens, which have just a single 44780, presumably then these are
also just 8x1. I've no idea what they were used in, but obviously a
machine that didn't need a full 16x1. As Oliver Broad said, why put
a 44100 in if it isn't needed ?

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2001\01\06@080151 by Peter L. Peres

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The 2nd set of 8 chars is probably mapped at offset +0x40 in the display.
Also make sure you set the display size select bit correctly. Use a card
fill to fill the entire display RAM and see what maps where (card fill =
A,1,2,3,4,B,6,7,8,9,C,1,2,... in this case to catch windows of 8 chars).

Peter

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2001\01\06@180859 by Arthur Brown

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hi Jinks.
is this the LCD that the second 8 characters are displayed as line two of a
16 x2 display.
the second set are not displayed unless you shift the characters left.

Re:GARDS Art.

{Original Message removed}

2001\01\06@193856 by Jinx

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Thanks for all your input re: the LCD. I've concluded the screen
is faulty as the display flickers if you even slightly flex the board,
so I've binned it. That's dumpster-diving for you, easy come,
easy go. Plenty more where that one came from. All of my old
routines are fine on any other LCD except the Acme-brand thing
and it just happened to be the only example of its make so I had
nothing to compare it to.

The EPE reference was a good one - more digestible than the
tech-talk Hitachi chip manual and a handy companion piece

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