Graphic Display Interface - the PCB story

How did I get myself into this pickle? It all started with a chat with a friend who mentioned he had been looking into displays and this type seemed good and the right price. The one I could afford was a graphic display of 128 by 64 pixels. I think the feature that really sold them to me though was the option to have the background in blue and the text in white. You may have noticed I like blue from my front path lighting.

I phoned Apollo Displays, the local retailers and asked a load of questions about these units and all the answers were pretty much good news. The one question I failed to ask though was the one about connecting it to the rest of the circuitry that I would build. This is what has driven this project as soon as I saw the connector.

I bought the development kit and a handful of the displays to practice on and they all arrived as promised after payment on pro forma invoice (in advance by cheque). The development board was useful and did demonstrate the unit pretty well but it was expensive at over a hundred pounds including a screen. There is sample code on the site in the form of a pdf file which I set to work on converting to run on CodeVision and an Atmel Mega32. Initially I used the connectors on the demo board and simply unplugged the supplied chip. I found some usful information on www.avrfreaks.net but for the most part the pdf was the key. Here is a pdf of the web page with the information on it. I mainly used the contrast tips on this page and to help work out what some of the constants were in the sample code.

Here are pictures from Apollo of the display and the development board.

After getting the code working on the development board I was faced with trying to interface the connector to a board of my own design. Only two problems now, designing the board and getting it right and finally buliding and soldering it.

The design was not too bad although I did make a few mistakes as always. This included getting most of the capacitors round the wrong way (different symbols on the schematic and my PCB package) and I also fed it 12 volts instead if 5 as per the specs at one point. The screen survived all my efforts to destroy it but I had to check a couple of times on the development board just to make sure.

Anyway, I like happy endings and this has one. Soldering the 30 pin .5mm pitch connector was not too bad after I perfected the technique. That was to smother the connections with solder and then remove the excess using solder braid. I use around 330 C to solder initially and about 400 C to remove the excess. Assuming no disasters it takes about 20 minutes to solder and test the connections of each 30 pin header. I have made a little jig to help with the continuity and short circuit testing which helped but a good pair of eyes and normal multimeter probes will do the job too.

These are the pictures of the finshed units which I am now using for development work. Note everything is surface mount except the headers which stick out the bottom and plug into the main board. In my designs I am now using the layout and simply inserting it into my design. I am not using these as daughter boards at the moment but who can tell in the furure. I have even included a small LED in the top right corner so I can tell when power is applied.

Click either image for a slightly better resolution image (about 50 - 60k)

Hopefully we will see these screens in some of my projects which are still under construction.

This page last updated on 5^th October 2003