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Discussion on: What was your first project?

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nickholmesde profile image
Nick Holmes

My first personal software project was a PCB design and layout software, written in 6502 assembler running on BBC Micro. The 6502 has a 64kb address range, and the BBC came with 32Kb RAM and then up to four ROM slots that could be paged into the &8000 to &BFFF address range. My Beeb had an adapter putting RAM in one of those slots, so I could load my program into that. I think the assembler itself was in another ROM, but I don't recall that 100%. My application registered a "star command", and could then be invoked from the command prompt with "*pcb". Very, very cool stuff, for 1984.

The designer itself worked on the basis of 0.1 inch grid. I built a character set of all possible combinations of line going from the centre to left, right, up and down. Each then had a variant with a standard through-hole in the centre. There as also a completely blank character, and one with only the hole.

A PCB design was then basically a 2D array of these special characters. Considering the computer only had 32Kb (kilo not mega!), this allowed for pretty big PCBs. The software supported two PCB layers, because I wanted to be able to make double sided boards.

A real novelty for that time - it used a mouse.

I also built a X-Y Plotter, using stepper motors. The plotter accepted three commands - Move To, Pen Up and Pen Down. It connected to the BBC Micro via the parallel printer port. The controller used a Z80 CPU. The pen itself with supposed to deliver ink on to an acetate sheet (which could then be used to photo etch the PCBs), but I never got the ink delivered consistently or opaquely enough. It never got finished, as I went off to uni.

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nombrekeff profile image
Keff

Cool stuff man! Thanks for sharing your stories!