So now, I feel like I'm really getting close to my ideal Apple-1 system. I've got the whole keyboard thing at a point I'm happy with. I'm making progress on my case, but can't go as fast as I would like. I've been thinking about that expansion slot. Right now there's an ACI sitting in it, and I have been thinking about the future and possibly adding a CFFA-1, especially with the thought that I could play Zork on my Apple 1! I plan on making my case large enough to fit the CFFA in the future, if I want to add it.
I've also been thinking about how I can jazz-up my build, and came up with one conclusion - it needs LEDs! I dearly love LEDs and love them when they're blinking. I added some power-line LEDs to my Mimeo at the top, so I can monitor all 4 power lines (+5, -5, +12, -12), but it's not enough! I was looking through the Apple-1 Operations Manual, and came across discussion of "Address Display" on page 12. Hmmm. It looks like a series of LEDs that can display the state of the address lines. I searched online, and found that speedyG has already built this here:
I'd love to build this and have it incorporated into my enclosure, and showing the activity of my Mimeo. I'd love to have it on all the time, but since I've got the ACI in the expansion slot, am I out of luck? I then looked to the side of the expansion slot, and saw the Mimeo's edge connectors sticking out the side, and wondered if I could tap those, build my "step-diagnostic-address-display-card" to plug onto that card edge. It looks like it's just parallel to the expansion card edge connector, and I was wondering I could just use the card edge and this way leave my ACI where it is.
The only thing I have seen that uses the card edge like this is Wendell's 3-slot expansion board here:
Now looking at his design, he uses logic to buffer address and data lines. Now I'm nowhere close to understanding this, but my vague feeling is that this has to do with switching control between the 3 cards on the expansion. If I built my board with just the address display and step/diagnostic switches, would I need to do anything like this, and still keep functionality of the ACI in the expansion slot already?
And another thing I'm getting a bit worried about is if I am over-taxing the power limits of the Mimeo. In my build, I could conceivably have the PS/2-serial adapter (with its microcontroller), the keyboard multiplexor (just a few ICs), the Apple II keyboard, the ACI/CFFA1, and possibly this address-display-card (with about 40 LEDs and some logic chips). Has anyone ever hit the limits of the power-supply of the Apple 1 with their peripherals? I'm guess if you attach the 3-slot expansion board and add 3 other cards, and if the Apple 1 could support that, I should be okay.
I would guess the duty-cycle of the address display LEDs should be somewhat less than 25-50%, and likely even lower. And if I limit them to 10mA each, that would put the estimated power draw of the extra LEDs alone at about 100-200mA.
Any help or insights by anyone on this would be a great help. Thanks!