A1200 hardware hacking

[Stedy]

in fact, Ian Stedman had a design to hook up an Intel 8255 chip to give 24 digital I/O pins from the clock port, but he has since changed it to use the parallel port

The design is done and I have a basic autorouted PCB but I have not built that version. For the parallel port version, I have the PCB next to me, got to get soldering.

If you want the schematic, I will upload it this weekend with the next updates.

To interface the 8255 to drive LEDs you would need a buffer chip like a 74245, as it has a crap source/sink capability.

[Stedy]

I take it a VFD would likely need a 74245 as well?

I do not know how you drive a Vacuum display. What voltage/current does it need?
A 74245 (8 bit bus transceiver) is a good idea for any outputs in case you screw up, you blow a cheap chip oh and has +/-32mA current capability per output.

Wiring up a bunch of switches should be pretty easy though?

Yes. You may need debounce circuitry though. You can use software or hardware to debounce a switch.

Take a look here for suitable circuits:
http://www.ianstedman.co.uk/Amiga/i_f_circuits/i_f_circuits.html

Ian

[Stedy]

Hello,

I have put the schematic of the Clockport 24 bit I/O card online at:

http://www.ianstedman.co.uk/Downloads/clockport-dio-card.png

If you want more details, just ask.

Ian