LCD Goodness

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jaem
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LCD Goodness

Post by jaem » Thu Dec 13, 2007 1:12 am

So... my friend and I (1st year EE students) got wind of Goldmine Electronics' sweet deals recently, and decided to order some loot. I seriously love surplus dealers... the whole mentality of "we have no clue what this is, or what it does, but we'll give it to you for $3 instead of $100 if you can find out" :P
We snagged an 8" IC wafer, and a bunch of grab bags. I'd recommend them to anyone who wants cheap stuff.
My best find, however, was a very nice Graphics LCD. It was included in their Displays Grab Bag - $5USD for 25 assorted displays. I figured that even if half of them didn't work, it would still pay for itself many times over. They gave me a whackload of 7-segs, and a 5x7 matrix (and threw in a couple light bars, just to be cheap), but then I saw the LCD... (pictures below)
It's a 65x128px B&W STN. Together with my (free) Cypress "WirelessUSB" (not "Wireless_USB", btw) module, I plan on making a wrist-mounted wireless terminal, because I am that much of a geek!

It has a spot for the Accursed Pink Foamy LCD Connector Of DOOM (APFLCOD), with ~20 conductors (my eyes go funny when I try to count them - especially at 11PM). Presuming it's a standard pitch, where would be my best bet to get a hold of one of those? Can you cut down a longer one? (e.g. from a calculator) Also, do you need anything special on the board to connect to it, or just pads? I haven't dealt with them before (because I've never had an LCD with clips that would actually allow me to mount it so the APFLCOD would stay in place).

I figured my best bet for controlling it would be a 32-bit AVR, since it has a GCC cross-compiler available. Could someone point me to some beginners/part selection info for them? Also, I need a cheap programmer for them. I have a laptop, so my COM port is not up to spec - as I asked in another post, could you hook the two parts of a MAX232 back to back in between the port and the device to boost it, so as to use a budget programmer? If possible, I'd like to kludge together something out of about $3 worth of stuff that I already have lying around :P

Thanks for any input...

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haklesup
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Post by haklesup » Thu Dec 13, 2007 10:52 am

That pink foamy connector is called an elastomer connector and the pink ones usually have a carbon conducting layer. Imagine a stack of alternating layers of conducting and non conducting silicone.

They also make silver and gold connectors
http://www.fujipoly.com/products/genPro ... Line=Zebra

In any case, what you need is an exact mirror match for the land pattern on the LCD but on a standard PCB. The elastomer connector is clamped between these two conducting planes. A board from a cell phone or calculator might not have the same land pattern.

part of a SMT to DIP adapter board might work. Maybe SOIC (50 mil pitch) or SSOP (0.8mm pitch) or TSSOP( 0.5 mm pitch)

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Dave Dixon
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Post by Dave Dixon » Thu Dec 13, 2007 11:54 am

Yup, we use "zebra strips" from FujiPoly where I work. (One of our techs called them "zebra stripes" for years - and no one corrected him.) Hackles explained it well. He probably knows - but took for granted something that I used to have all wrong. Generally the pitch of the elasto-strip will be an order of times finer than the pitch of the LCD and PCB pads(The LCD and PCB pad layout must be identical, as stated previously). This assures that a MINIMUM of one conductor makes contact, and a MINIMUM of one insulating section will be between the contacts. I used to think that everything lined up perfectly at the same pitch. Regards, Dave

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jaem
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Post by jaem » Thu Dec 13, 2007 3:06 pm

Thanks guys! btw, I checked with a friend, and the MAX232 thing should work - I'll try that.
I'm having a bit of trouble with the permissions settings on my school's server, so I can't post pictures right now, but connecting to it shouldn't be a problem. the LCD is inside a metal shell, with a plastic backing clipped in. The shell has metal clips and pegs to hold a board in place, and the plastic part has a slot for the "elastomer connector" (thanks for the name :P), so it won't slip either. I was actually wondering if I could cut down one of the connectors (providing it was suitable) to fit in there. I figured the chances of me randomly finding one with the right pitch *and* length were pretty slim. I noticed when you hold the strips up to the light, the conductive parts have a different shine to them - does that finish delimit the whole conductive area, or is it smaller?

I'm going to ask what my university has in the way of board fab tools - for a ~1.5"^2 board, I don't think they'd care if I used their etchant or whatever for non-school stuff. If they don't have good enough stuff, where's the cheapest place to get double-sided boards online? (e.g. 1 or 2)

I'll start a new thread about the AVRs, so it's easier...
Thanks,

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jaem
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Post by jaem » Thu Dec 13, 2007 8:42 pm

Here's pics of the screen, for those interested...
notice the slot for the "elastomer connector", the clips and, optionally, the numbers. I've looked it up on http://alldatasheet.com and got the full 65-odd page datasheet from Samsung for the controller. It's nothing fancy, but it has some nice features, such as inversion/on/off of all pixels without modifying the data RAM. It also has sleep/off modes, and supports 3 or 4 wire SPI, as well as 6800 and 8080 compatible parallel modes.

Image

Image
[click on images for larger version]

If you can't read the codes, it says (in order):

79Z93 SDI 13-04 S6B0755
H2.80 REVERSE U6-09B63-AA A31

the number S6B0755 turns out to be the controller's part number (isn't it nice when the first number you look up is the right one? :P) I haven't checked the other ones yet.

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jaem
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Post by jaem » Fri Dec 14, 2007 12:41 am

I just Googled another number on there - FIRST Google result!
http://tim.cexx.org/?page_id=342

Everything anyone needs to get started with these LCDs - which, btw, are also available separately here

The first link also has a breakout-board pattern in PDF - here, in case the comment is somehow deleted

They come from a motorola v66 flipphone, according to a commenter who took apart his mom's phone.

All that remains for the present is getting a compatible zebra strip (1mm pitch) and getting the money for the breakout boards :(
It turns out that only SPI mode is available on this assembly - the blogger (Tim) actually took apart one of these displays, peeled of the covering on the COG, took a picture, and played with filters until the (Indium-tin Oxide) traces showed up enough to match to the controller datasheet. Tim, if you're reading this, you're now officially my hero...

at the risk of appearing to spamdex, and to help others in their quest, I offer to users of The Oracle some helpful keywords:

79Z93 LCD S6B0755 GOLDMINE

:P
seriously, though - if anyone needs a really hobbyist-friendly, cheap LCD, buy this one.

I may be able to use the university's equipment, but failing that, (to reiterate) what's the cheapest (including shipping) board fab that does ~<2"^2 boards in quantities of 1-3?

EDIT: there don't seem to be any that I could call cheap (at least not when I'm broke) - and why the heck does one of them add on $115/board for 0.031" thickness instead of 0.062"??!!

zapped
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Post by zapped » Wed Dec 19, 2007 10:42 am

Check out the 280x220px color TFT that comes with a v8 uRISC processor and a USB interface you can use to program it. It also has a 1302x1031px CMOS imager that you could remove and use the I/O lines for connecting your keypad or wireless transceiver or whatever you dream up. It comes with 16M NAND FLASH and 8M SDRAM. It also has a flash circuit that you can remove so you don't get zapped like I did. Oh, and all these neat parts and several I didn't mention come soldered on their own printed circuit board included at no extra charge!

http://www.maushammer.com/systems/dakot ... l/lcd.html

http://camerahacks.10.forumer.com

http://camerahacks.wikispaces.com

There hasn't yet been a gcc port done, but you can download a demo of Hi-Tech's C for the Arclite or use the open source pv2devkit assembler.

You can purchase one of these at your local CVS or RiteAid or Wolf camera and maybe some other places for about $10 on sale.

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