How to connect a payphone's VFD to your PC
Written by Chris D.
In this article I describe how you can connect a payphone's display to your pc for a neat little desktop readout.
Required Parts:
- Noritake CU20026SCPB-t23a Vacuum Fluorescent Display. This is the green 20 character by 2 line display found in the Nortel Millenium payphone.
- Solder Iron, solder, etc
- An old printer cable (or any cable that plugs in to your parallel port and has all 25 pins wired)
- A 25 pin DSub connector (male or female, depends on the cable you are using)
- A 40 pin IDE ribbon cable
- Some means of getting +5 volts to the display connector (I used a ps/2 passthrough connector)
Let's get started...
This guide is for only one type of display: the noritake CU20026SCPB-t23a. This is a custom model that you can't get from Noritake and they won't even give you datasheets for it. The display doesn't even seem to share the command set common to other -t23a models and instead it seems to have a mix of standard and non standard commands. You could probably use what's in this guide to help you hook up some other display but you'll have to use your brain a little. I'm not an expert on these displays and I don't know how to connect any other models so please don't email me asking how you connect some VFD you bought on ebay.
Don't email me asking where to get a CU20026SCPB-t23a either because I don't know. All I know is that the Nortel Millenium payphones (both the desktop and the freestanding ones) use this display.
Here's what the display looks like:
Note the single 26-pin connector on the back of the display. This sets the display apart from 99% of the other displays out there: it has power and data signals in the same connector - most displays have the power connected separately.
Wiring Is a Bitch...
well it isn't that bad at all actually, it just took me a while to figure out what wire does what.
You should be able to wire yourself some kind of harness using this diagram. If you get your power from the PC's power supply then you don't have to connect the grounds from the parallel port and you save yourself some trouble.
Software
There is some software out there to control various LCD and VFD units but I couldn't get any of them to work for me so I wrote my own. I don't guarantee or support the software in any way, but if you use it and it works for you please send me an email. You'll need .net 2.0 to run the software.
This app is a basic one that tests the functions of the vfd so you know you've got it connected right.
This app will show you a clock and scroll the titles of newsfeeds on the display. Still working out some corruption issues with this one.