Newbie looking for help on getting/building 20x4-LCD

zdragon · Post by **zdragon** » June 17th, 2006, 4:25 pm

Okay people so I tested LCD smartie out today with the help of PalmOrb and I'm amazed and want to build a "real" LCD now (as the PalmOrb one always has to be turned on on my Palm first, I may not have Hotsync running at the same time, etc. pp.).

The thing is, I'm not doing much with electronics, so I'd probably need help for this as the pre-build LCDs are quite expensive, and hey it's more fun to do it yourself anyway. But I neither know how and where to get all the stuff that I'd need for the 20x4 LCD that I want (I live in Germany) nor would I know what to do with all that stuff then once I'd have it lying on my table here :p I guess I at least know how to use the schmatics e.g. provided here, yet I don't understand a single thing about them on the other hand and of course it would be fun to be able to add features to my own LCD. I'm a hobby C++ programmer (without experience in .net though), but I'm not sure if that's gonna help at all :p

PS: What I'd like is to something for my parallel (LPT) port and I want an LCD with backlight, too.
Well, any input would be appreciated ^^

Post by **mattcro** » June 18th, 2006, 12:00 pm

Whichever way you do it (serial port or parallel/LPT port), building your own LCD for use with Smartie (or other software) requires some electronics knowledge - at least reading a schematic and soldering. It's definitely more fun and satisfying than just buying a complete module from a computer shop. Plenty of folks on this forum have built their own.

The parallel port is the easiest way to connect an LCD to your PC. It's just soldering wires to a 25-way connector and to the LCD module, plus a couple of components to drive the backlight. This page has info on parallel wiring and links to instructions for building the circuit.

The serial port method is more complicated and requires soldering at least 1 chip (like the schematic you mentioned) but it's more versatile because you can add buttons to control your media player etc.

Do you know anyone who can help you with the construction? If you haven't done any soldering before, this is not the best project to start on because it is possible to damage your computer if you get the wiring wrong. But if you are careful, it should be fine.

The only electronics supplier in Germany I know of is Conrad but there must be others. I know the UK branch of Conrad stocks LCDs and the other parts you need. The cheapest place to get LCDs appears to be ebay stores like Rainbow City who ship all over. Check import duty and postage, though.

That should be enough to start with. First, see what sort of LCDs you can find in electronics shops (4 line of 20 characters with LED backlight is what I have). It's probably best to keep it simple to start with and use the LPT connection.

Matt.

zdragon · Post by **zdragon** » June 18th, 2006, 2:41 pm

Okay, I've gotten a bit further.
I searched around in the garbage and found an old fax machine with an LCD display. This is a (bad) photo of it: http://mitglied.lycos.de/dragondubs/100_2725.JPG

Is it okay to have only 14 pins and therefore just ignoring any kind of backlight stuff for this one? Meaning I won't need any resistors etc. for now?

I'm not sure if the controller still works, but at least I've gotten it to work to display a pattern like this by setting Vss and Vlc to ground and Vcc to +5V after this schematic: http://www.jalcds.de/images/4x20wobacklight.gif

[x]=black box
[ ]=white box (=nothing displayed there)

It displays this:
[x][x][x][x][x][x][x][x][ ][ ][ ][ ][ ][ ][ ][ ]

What is that display now? 1x16? Or maybe 2x8? Is it normal for the right part not to get displayed, even without any wiring but the power?

Right now I'm working on the LPT connection, just soldered all the ground wires together and now going for the others. I'm using an old IDE cable as wires (as they are already isolated from each other). Any tips on how to make them stick in the female LPT cable that I have here...?

Smayds · Post by **Smayds** » June 18th, 2006, 3:43 pm

Looks like you've got yourself a 16x1, for free. Good job! Hopefully it will be 44780-compatible*

All you have to do now is hook it up to a DB25 plug and it should work with Smartie - although you probably want to add the contrast pot.

LCD displays tend to fill their first line with blocks when they are powered up. The reason the display is half-filled is because some 16x1 displays behave like 8x2 displays, but side-by-side on a single line. LCD Smartie should correct for this, just make sure you select 'Fix 16x1 line addressing' in the HD44780 options box.

*EDIT: DUH, it says so on the chip

zdragon · Post by **zdragon** » June 18th, 2006, 4:35 pm

One question - I'm currently soldering that thing, and for someone like me who solders once a year or so, it's incredibly hard to not make any mistakes.
Just in case, if for some reason one of the data pins (D0-D7) should be linked together or in case I should miss one of those - what would the behaviour of the display be? Like, missing a line, or rather not work at all...?
Any tricks to test the wiring before I connect it to my PC...?

EDIT: WIth the LPT female cable, it's really lots of work to attach the single cables to the pins. For the male one also. Is there any way to do the wiring by soldering the wires directly, like cutting the big LPT cable and doing it for each of the small wires? I mean, I'd need some sort of color keying of the cables for that, as there's no way to know which cable belongs to which pin otherwise t_t
How do you guys attach the pins to the LPT cable?

EDIT2: It doesn't work t_t Just the same test image getting displayed... anyway, I guess the process was anice experience and I guess I already got a few ideas on what and how to do better. So I'll order myself an LCD now I guess...

Post by **mattcro** » June 18th, 2006, 8:15 pm

Did you add the contrast adjustment variable resistor (marked 10K on that schematic)? If you just connected pin 3 on the LCD (the contrast control pin, called Vlc) to gound, the contrast might be so high that any characters will show up as black blocks like you saw. If you can find a 10 kiloohm variable resistor or even a 1k ohm or so normal resistor, you should connect that to the contrast pin.

Are you trying to push the wires from the LCD into the connector on the parallel cable? If you can get hold of a spare 25-way connector (either get a new one or salvage from a PC I/O port bracket or printer cable), solder the connector to the LCD cable to allow easier and safer plugging/unplugging. You could chop one end off a printer cable and strip the cable to get at the wires, but it's a hassle identifying which wires go to which pin - needs a multimeter and some patience, unless the remaining connector can be opened up. I don't think there's any standard colour code.

It looks like that LCD does not have any backlight. 1x16 LCDs work internally as a 2x8 layout, which might be why only the left half shows up as blocks. The whole display should work properly when it's properly configured by the controlling software (like Smartie).

If you get the wiring wrong, the result could be no response at all, or characters jumbled up, depending on which wires are wrong. Just take it slow and double-check the wiring before firing it up.

Salvaging stuff like this is a good way to get started - you get practice at hooking up an LCD and soldering without the risk of frying a valuable LCD you've just bought. My first attempts at hooking up an LCD to the LPT port were with a 2x16 display salvaged from a junk fax machine too.
Matt.

zdragon · Post by **zdragon** » June 18th, 2006, 10:22 pm

Oh hell, soldering all those wires to the male 25-pin LPT connector really was some long work.
Unfortunately, simply nothing turns up on the display...
I don't believe that the contrast grounding is the problem simply because only half of the display shows up in black. If it was the whole one, it would already be nice and probably be the contrast - but it isn't :-/

And I really triple-checked all the wires. I guess that the controller might just be broken from an earlier mistake where I attached Vss to +5V and Vcc to ground by accident. The controller was HOT. Well, shit happens :p

Post by **mattcro** » June 19th, 2006, 12:10 pm

I destroyed my second (fortunately also salvaged scrap) LCD by connecting the power up with the wrong polarity, so you may well have fried yours. The symptoms were the same - blocks displayed on power-up but no response to commands. It's not too hard to destroy them, but don't be put off trying again.

Maybe you can find another junk fax machine...

Matt

zdragon · Post by **zdragon** » June 19th, 2006, 2:14 pm

I just bought this one:
http://cgi.ebay.de/ws/eBayISAPI.dll?Vie ... %3AIT&rd=1

Cheaper than Conrad

Guess I'm just gonna experiment with it... any advice left, e.g. for soldering or whatever else? or should it just work already? :p

Post by **mattcro** » June 20th, 2006, 9:51 pm

Very nice. Did you get the kit shown in the "contents" photo further down the page? If you follow the schematic they give (lots more soldering

!) it should work fine with Smartie. At least with the kit you have a nice new LPT connector and proper cable, plus the variable resistors to control the contrast and backlight properly.

Solder the LPT connector to the cable first to get some soldering practice, then solder to the LCD. The two variable resistors will just have to hang off the cable. Good luck!

Matt.

Hmm, I notice they don't have Smartie listed as one of the programs to use with this LCD...

zdragon · Post by **zdragon** » June 23rd, 2006, 5:30 pm

Mh, now whatever program I use, it just won't work with my LCD O_o
The first time I started it up, first I saw just nothing, then changed the contrast and backlight and finally got two of four lines displayed, as it should be.

But now nothing works. Everything's soldered absolutely correctly, I triplechecked it... so why won't it work?
Also, the vendor I got it from says that it was tested just yesterday (weird though, I got an email that it was sent one day before it was checked O_o). Dunno, still believe I'm doign something wrong here. BIOS is configured to EPP 1.9, is that the right version? My BIOS can also do 1.7 if that would help in any way... I'm also using the correct address in the BIOS (378) and the same in LCD smartie and jaLCDs. DriverLINX Port I/O is installed of course.

What else could I be doing wrong?

_X7JAY7X_ · Post by **_X7JAY7X_** » June 23rd, 2006, 7:53 pm

I have lost 2 LCDs to the parallel port before. They were hooked up correctly and working fine for a while then just stopped working. I have not hook any more LCDs up to the parallel port since. I talked to Crystal Fontz, they wont warranty LCDs hooked up the parallel port. He said that they go will go bad (premature failure) and he thinks its from ESD. He made it sound more like not if they will go bad but when. Although some people on here have had no problems with the parallel port and they have been hooked up for a while.

J

zdragon · Post by **zdragon** » July 2nd, 2006, 12:10 pm

I've been measuring a bit and found out that the LCD pins 5, 6 and 10 (according to the schematic here) seem to be getting just no info at all when I'm running the "standard" LCD smartie screen.
At least the DC is always at 0 there (I measured between mass and each of the pins on the LCD). I cannot say if this is because of the values changing rapidly (I only got a small analog multimeter and no osciloscope), but I find it rather weird.

I checked my wiring though; the LPT cable is properly connected with those pins on the LCD. Is it alright how it is and is my LCD broken after all (it's getting info everywhere else, just not at pins 5, 6 and 10), or did I forget something while wiring or what?

Post by **mattcro** » July 2nd, 2006, 1:40 pm

It sounds like you're not having much luck, which is a shame.

It could easily be that you just can't see the short bursts of data that should be present on the data pins. Can you see some sign of activity on the other pins, but nothing on 5, 6 and 10?

Pin 5 on the LCD is the read/write control. I think this is always 0 (low=write to LCD), but it might go high for a very short time after a command is written if the software (Smartie) uses the LCD's handshaking system.

Pin 6 on the LCD is Enable, which is pulsed high for a very short time each time a character or command is written. Your meter might not detect this.

Pin 10 carries data bit 3, so you should see some activity on this pin.

Try unsoldering these connections from the LCD and measure the signals on the cable to see if there's any activity. You should see something on the D3 connection at least.

It's possible that the corresponding pins are damaged on the parallel port (maybe from the previous LCD??). Can you try on a different computer?

Are you getting any characters on the display (even if it is random garbage)? Or does the display always show the solid blocks on two lines that appear when you connect the power?

When you use Smartie to test the display, try to use a screen configuration that includes something that will change frequently, so the display is always updated, like the time: $Time(hh:nn:ss). Otherwise Smartie only sends the data once (a single short burst) because the display never needs to change.

I don't know if any of that will help, but it's worth a try!

Matt

zdragon · Post by **zdragon** » July 3rd, 2006, 1:13 pm

Mh, I guess it's simply fried after all, but I'll try again.
I just saw an 4x27 display on eBay - does LCD smartie support it? Or is there any way to make it work with it? Otherwise I'd have to use a different program...

EDIT: And another question: is it possible to install a backlight from an LCD although it doesn't have one by default, or is that rather advanced knowledge? How can I make an LCD without backlight still appear good and readable in the dark?

Post by **mattcro** » July 6th, 2006, 4:15 pm

I don't think 4x27 is a standard sort of display that Smartie would support, unless it's some kind of custom LCD (the glass panel) with a standard HD44780 type controller. Hard to tell.

I remember seeing an article somewhere on the net about retrofitting a backlight to a standard LCD. It involved disassembling the LCD, peeling off the reflective backing and inserting an electroluminescent (EL) panel, then reassembling. It would be easy to damage the display, and you need to find a suitable EL panel and driver circuit.

The simple, but not so elegant, alternative is to illuminate the LCD from the front, like the Dirk-o-Tron.

It may also be possible to illuminate the LCD from the sides if you cut away some of the metal mounting frame and shine some LEDs into the ends of the glass panel.