nick@lfcs.ed.ac.uk (Nick Rothwell) (04/17/89)
I've had a lot of mail asking for the schematics of the 10 quid Mac MIDI interface, so I'll try to get round to MacDrawing it as soon as possible. I have the original Kirk Austin MacDrawing on-line here, if anybody would like this. Actually, we still have a minor technical problem to solve. For some reason, the MIDI interface idles with current on: if the Mac is switched off, the interface's Mac->MIDI LEDs go on, and it holds the MIDI lines high. If I run any MIDI software, it works fine. In addition, Performer and MIDIscope leave it in a good state when they exit. If I reboot the Mac, the lines go high again, and off we go... You don't want to know what a constant high MIDI signal does to a synth. The TX7 loses its marbles and will happily randomise its patch memory. The D-50 merely rumbles and spits into its audio output... I suspect that we're interpreting the RS432 signals wrongly, and are using the wrong earth connection or something. Can anybody in the know throw some light on this situation, by explaining the correct RS432-MIDI pin assignments? Anyway, we'll try to track this down as soon as I can bring myself to once more squint at a tiny PCB covered in Verowire... The dual-colour LEDs look great, by the way. Nick. -- Nick Rothwell, Laboratory for Foundations of Computer Science, Edinburgh. nick@lfcs.ed.ac.uk <Atlantic Ocean>!mcvax!ukc!lfcs!nick ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ...while the builders of the cages sleep with bullets, bars and stone, they do not see your road to freedom that you build with flesh and bone.