The User Port Lead

All you need to make this lead is a small vice, a length of 20 core ribbon cable and two insulation displacement sockets with 20 connections. When assembling the cable it is important to note that there is a phase reversal, ie the marker strand - often red - is on opposite sides of the two plugs when seen side by side. The drawing below may make this point a bit clearer.
The user port lead

You can buy special tools to squeeze the ribbon onto the plug, but I found that a small vice will do the job just as well, if not better. Give me a shout if you have trouble.

 

The Printer Port Lead
This one is a bit more difficult, because you need a soldering iron. It is best to start with a printer port lead that has only one socket connected. The other side has to be soldered into a 25 pin D-type plug which is standard for all printer ports. The drawing below outlines the connections.

Most of my projects use the same kind of lead, so one works with all of them. Only the two atomic clock projects are different, because they only use one line.

The printer port lead

If you plan to use the printer port, here is a little warning sent in by Tony Williams:

One comment; I notice you discuss using the RPC printer port for i/o experiments. I would not advise you to do this. The printer chip in the RPC is a huge combo chip, that controls many facilities. Damaging this chip can ruin the RPC and be very expensive to replace. I know, I wounded my printer port with a simple accident with a PIC programmer. :-(

I have had no problems so far, but then I generally use the user port, which is very robust indeed. You have been warned - if you use the printer port, take extra care!

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