Back to the 80's…

15 Jul, 2008
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Overview of the CTA display and the PC that runs the socket server allowing tcp/ip access to the display

One of the challenges we are facing in our project is connecting antique display devices to the brand new travel information system we are building. If you have traveled by train in the Netherlands you are familiar with them: large displays with booklets for destinations and departure times. It contains a number of booklets which are controlled by a stepper engine. The devices are called CTA’s, were developed in the eighties and are a solid piece of engineering. Behind the track indicator, which doubles as a door, is a temperature control for the heating, a power socket for connecting electrical equipment, a telephone socket and a connector for testing. Oh yes, did I mention it is heavy?

These CTA’s are controlled using a serial protocol over thick copper wires. The software we are developing will run on large LCD’s, but until all current CTA’s have been replaced, our new software has to cope with these old displays as well. So what do you do if you are developing software that controls 400 pounds of legacy via a serial line? You want to get your hands dirty! So we arranged for one of those beasts to be delivered to our team room a while ago. It came out of storage after having spent a life time, about 25 years of faithful service, on a platform somewhere in the Hilversum/Amersfoort area. We received the CTA complete with bird dung on top. Luckily, the movers got their hands dirty and cleaned it up a bit.

CTA’s are controlled using a protocol named Krone, after the German firm that developed the software. We had extensive documentation, created on a typewriter, in German. Being Dutch we sort of manage reading German, but our Indian colleagues were lost, so the first hurdle was translating the protocol spec. I volunteered and now we have an electronic English version. Great. Days later, we could make the CTA spin. A true victorious moment. Two of our Indian team members spent a few weeks in the Netherlands and got a first hand look, but they could not stay until the end and had to go back to India. So what do you do if you are working in a distributed agile team and need to share one heavy CTA?

Our favorite solution as honest IT professionals is to use technology where possible, so we bought a webcam with an network interface, connected the thing to the network and aimed it at the CTA. We made the serial port available as a tcp socket and now we can test, wherever we happen to be and see what the results are. All to support our Agile way of working. The only disadvantage for Jan and myself is that we are sitting next to the thing. Every now and again we are startled by rattling sounds from the beast. Given the time difference with India, this must happen to cleaning staff as well…

Make it spin!The CTA display in a set state


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