IBM 4820 touch screen

lez · 01-23-2004, 12:25 PM

Well on the grounds that bigger is better I went and found one of the ibm 4820 touch screens on ebay, often used on shop counters / POS areas etc.

If you get the 4820 4ft, it takes analog rgb (vga), and serial for the touch screen, power is 12-16 volt(yippee!).
They also do usb, and DFP signal versions, make sure you get one that will work on your graphix card, as most of these POS units are digital.(vga)

Problem?

LOTS! AS YOU CANT BUY ANY DAMN CABLES!!!! IF YOU FIND THEM THEY COST MORE THAN THE MONITOR!!!!!!!

the connectors are non standard, small 20 pin thing for the vga which vesa have decided is a DFP digital panal connector, and not designed for analog, so vesa website has only a digital signal pinout, ibm has no pinout, and after 6 hours of downloading pdf files from ibm I still have no pinout.....

Does anyone have a diagram for a 4820 analog imput socket?

Next option is to open it (very simple) and see what chipset is used for the A/D conversion, get a data sheet, trace input pins back to socket, and solder a long cable on as I cant buy a plug either....

Then I have to work out the rs232 connections from the silly 8 pin socket they have fitted.

cvi · 01-23-2004, 04:10 PM

Any of these connectors?
take a pic of the connectors and the screen, and someone might be able to help you.

lez · 01-25-2004, 02:19 PM

Oh yes its the one marked digital only, thats why ibm are using it for analog vga........

They do produce this screen in analog only and digital only versions, and use the same connector for each, no doubt in my mind thats to save money.
Problem is I can only find how to connect it up for digital input, which is no good as this monitor is analog only and so is my gfx card!
The vesa site has the pinout for the digital type, thats a vesa standard called dfp

At this point in time its in bits all over the front room floor, I've taken lots of photo's, scanned the boards, googled away for hours getting datasheets for all its chips, now I have to work out how its all put together.(diagram style)

It has a tmc 1203 (http://www.fairchildsemi.com/ds/TM/TMC1203x20.pdf) a/d converter so the rgb side is now under investigation, it has 2(2) 232cb serial converters so that will give some idea of where the rs232 is going for the touch screen, just not found anything for the h/sync v/sync yet.

will try to get all this on web later.

lez · 01-25-2004, 02:22 PM

just like to add ibm have got back to me on how to connect this monitor to a standard graphics card, and have two options, one is to /buy/ their cable, two is to /pay/ for tech support with my credit card.

I'm still running on option 3, trace the signals back to the plug.

lez · 02-03-2004, 12:36 PM

Ok I have the vga side working now got to win the fight with the touch controller....

inside it has 2 rs232 converters, so it can support 2 channels of serial, but I dont know why....

I have tried both and the software from the ibm/3m website, nothing working so far, if anyone knows of /any/ touchscreen software that works in XP with a screen on a serial port can you tell me where to download it, maybe it will see this screen etc as most serial software is fairly generic.

What software is used on lilliput, thats probably good enough etc

Skraggy_uk · 02-05-2004, 07:35 AM

Probabley already been here but Is this of any use to you?

lez · 02-07-2004, 07:54 AM

yup started their, got them, says no screen detected.

I think I have an rs232 problem between pc and screen but cant work it out.

Boy I wish I could find a 4820 cable for an hour!

lez · 08-21-2004, 10:53 AM

Just worked out the pinouts and posted them on the uk site, you can find them their.

lez · 12-07-2004, 02:57 PM

Grief I'm still fighting with this damn display, beginning to wonder if touch side is dead etc and that why I cant build a working cable.

But, as my cables are experimental having no diagram to follow, could be bad wiring.

but if any one sees a cable or can buy a cable(cheap!) part number 07K6156
or part number 10J0860 help me out here!

even if its too far to ship etc its only the information needed to wire it.

these things must have been sold by ibm in thousands, 12 inch epos units etc with serial touch, some one must have an old one somewhere.

lez · 09-01-2005, 03:58 PM

And a year later I still have not got this to work!

tonight is last attempt, kill or cure...

going to start with rxd and txd from com2 and just connect to every pin on the socket in turn till the software says screen attached or I run out of pins.

(or the mb com port dies!)

lez · 09-01-2005, 06:42 PM

O k hours of soldering and here it is.

counting pins on bottom row of silly 14 pin connector working away from vga socket, pin 2 to comport pin 2 , 3 to 3 and 5 to 5. voila.

2 and a half hours of soldering and running the screen finder to get to this, because I was working form pin 14 down........

After 18 month of trying to get a cable etc I have finally cracked it, to find the touch screen is duff! No wonder I was sold it without cables....

Passes all selftests but wont see a touch on the screen.

So if you see or buy one of these, you can now wire it.

At least I can use it as an lcd

Scouse Monkey · 09-01-2005, 07:02 PM

try and find a new controller. If it is a 4 wire resistive then get a controller off a xenarc or lilliput or from digitalww

lez · 09-03-2005, 07:28 AM

Controller is saying selftest passed, so I am guessing its the screen.

If I plug the touch overlay in wrong it says h/w fail so controller seems ok

I am waiting to try the screen on another known working controller, but its a capacitive controller off a CRT and this screen is a resistive overlay, the controller is microtouch and I think they autodetect. (hopefully)

I also hope to try plugging my controller onto the CRT capacitive pad to see what happens, but its getting to be a wireing jungle having two screens in bits and cables joining all the boards and psu's

lez · 09-03-2005, 05:23 PM

well many hours later.........

All working but one corner of the touch overlay is damaged so can only use half the screen........

grrrrrrrrrrrrrrrrrrrrrrrrrrrr...

Time to buy new one!

lez · 09-04-2005, 08:22 PM

bwah ha ha ha ha....

Silver conductive paint is my friend!

bought it years ago (about 10!) to fix a keyboard overlay on an amiga a500, but painted it on the glass after being careful to lift one corner of screen and I have a touch screen!

This paint used to be sold to repair rear window heaters on cars but not seen it in years.

Its not perfect, if I draw a square with my finger I get a shape thats like an inverted diamon, IE where the points of the diamond should be the square shrinks in, but its useable.

Its not good enough for windows but now I just need to design big icons to press for my apps and away it goes!

Approaching 2 years and many hours (at least 5 just tonight!) but its paid off, well better than throwing it in the bin!