Scor­pio News

The PCB program is rather limited, but apparently it is only a “taster” for a better version (see later). If you are designing a single sided PCB less than 3 inches square and don’t mind copying it off the screen (or writing your own dump routine), and also are of a patient nature then it is very good. I have found two bugs in it. One relates to track delete and is mentioned in my letter. The other bug is in track move, where if, having chosen and marked your track, you move the end over the end of another track then the second track is picked up and moved as well. This is not so easily fixed, but armed with the knowledge it can be avoided. I have used my re-written version of this program (which supports extra facilities) to design an interface board for my Galaxy and have found that it does speed up the process considerably. I had to take a dozen intermediate hard-copies (this was mostly because I was doing a 5″ x 4″ double sided board, but not entirely) so I feel that the lack of a hard-copy facility is probably the most serious drawback.

The other program supplied on SVC-03 is the source for the GM575 SVC-graphpac. Doctor Dark has covered this briefly in the last issue so I shall not cover it again here. What I shall say is that I found a bug in in it within half an hour. I mentioned this in my letter in which I also mentioned how to correct it. For my troubles I received a copy of GM575 to check. The bug. for I still feel it to the such, is indeed present here, but all the demonstration programs cater for it by using the MBasic RESET instruction immediately before any use of GSI or PSI. I don’t know whether the manual instructs this but the modification I gave removes the need for it.

As regards the claim that this “could be used as the basis for own commands”, I feel this is a little hopeful as the source is sparsely commented and written in a very confusing manner, but what do you expect ?

All in all a good package, well worth the £20 (this includes P&P and VAT).

A Better PCB Package

And one which does most of what mine does! Actually it does some things mine doesn’t (yet).

The version I have is a “pre-release” (nth revision prototype) version, so I shall attempt to be “honest but not too destructive” as my instructions say. It has been written by the same person as the simple version in SVC-01 and -03, and he will be selling it directly for £20 + VAT.

I noticed immediately that the bugs I mentioned have been fixed. This version caters for boards up to 8.6″ x 8.6″, handles double sided boards and includes a dump routine for Epson compatibles (the width is restricted to 8″ for this) Also added are 3 new types of pad and rotated versions of two asymmetric types. The IC package facility is extended to include 64 pin packs, but for some obscure reason it docs not support 20 pin ones.

Well those are the good points.....

I’m afraid I have to say there are several things I would want done differently. These relate mostly to the methods used to implement the improvements.

Firstly, the extended size capability. Because the SVC display is too small it is obviously necessary to have only a section of the board displayed at any one time, at least while work is being done. The system used divides the board into 9 segments roughly 3 inches square. At any one time there will be one of these on the screen and the others not visible. Unfortunately the boundaries are fixed and there is no overlap. The result is that there is a “noughts and crosses board’ of almost un-usable bits which are impossible to see clearly. Anyone who has tried navigating across the boundary between overlapping maps without being able to see at once will know how tricky it is. The solution would be to allow any section (or at least one of 16 or more overlapping sections) to be displayed.

To make this worse, the boundary zones cannot be crossed by tracks so you have to find the meeting point and define two tracks. This process is painful, and on the demo. PCB file it has obviously caused some confusion at one point.

The double sided facility is also bound to cause problems with the two colour (on / off) display. This has been done by displaying one side or the other but not both. This makes sense but without the facility to display both sides simultaneously (at least temporarily) it is still quite difficult to use.