Designing an Apple 1 interface card

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Designing an Apple 1 interface card

Postby jrsharp » Oct Thu 22, 2015 2:03 am

Hey all,

I dusted off my Replica 1 recently in the interest of developing an interface card for it. I'm developing a flexible card with some reprogrammability, but with an initial purpose of interfacing an ESP8266 WiFi module with the 6502.

I've got an etched and assembled board, and it powers up the components on the card fine. (no smoke!) However, the monitor behavior changes when the card is installed. When I read memory, I get erroneous values. Normally, A000 contains the compiled A-through-Z example from the manual. Here's the output I get when the card is installed. My PSoC4 microcontroller on the card is only reading address/data bus lines... that is, the pins are defined as inputs only. And... here's the kicker... I get this behavior whether my micro is installed in the socket on my interface card or not. In other words, I get this behavior simply by plugging in a card with copper traces that just connect to a socket footprint. I'm kinda stumped here. Any ideas?

Code: Select all
A000.A100

A000: A0 A0 A0 A0 A0 A0 A0 A0
A008: A0 A0 A0 A0 A0 A0 A0 A0
A010: A0 A0 A0 A0 A0 A0 A0 A0
A018: A0 A0 A0 A0 A0 A0 A0 A0
A020: A0 A0 A0 A0 A0 A0 A0 A0
A028: A0 A0 A0 A0 A0 A0 A0 A0
A030: A0 A0 A0 A0 A0 A0 A0 A0
A038: A0 A0 A0 A0 A0 A0 A0 A0
A040: A0 A0 A0 A0 A0 A0 A0 A0
A048: A0 A0 A0 A0 A0 A0 A0 A0
A050: A0 A0 A0 A0 A0 A0 A0 A0
A058: A0 A0 A0 A0 A0 A0 A0 A0
A060: A0 A0 A0 A0 A0 A0 A0 A0
A068: A0 A0 A0 A0 A0 A0 A0 A0
A070: A0 A0 A0 A0 A0 A0 A0 A0
A078: A0 A0 A0 A0 A0 A0 A0 A0
A080: A0 A0 A0 A0 A0 A0 A0 A0
A088: A0 A0 A0 A0 A0 A0 A0 A0
A090: A0 A0 A0 A0 A0 A0 A0 A0
A098: A0 A0 A0 A0 A0 A0 A0 A0
A0A0: A0 A0 A0 A0 A0 A0 A0 A0
A0A8: A0 A0 A0 A0 A0 A0 A0 A0
A0B0: A0 A0 A0 A0 A0 A0 A0 A0
A0B8: A0 A0 A0 A0 A0 A0 A0 A0
A0C0: A0 A0 A0 A0 A0 A0 A0 A0
A0C8: A0 A0 A0 A0 A0 A0 A0 A0
A0D0: A0 A0 A0 A0 A0 A0 A0 A0
A0D8: A0 A0 A0 A0 A0 A0 A0 A0
A0E0: A0 A0 A0 A0 A0 A0 A0 A0
A0E8: A0 A0 A0 A0 A0 A0 A0 A0
A0F0: A0 A0 A0 A0 A0 A0 A0 A0
A0F8: A0 A0 A0 A0 A0 A0 A0 A0
A100: A1


And here's another output from F000-F100:

Code: Select all
F000.F100

F000: F0 F0 F0 F0 F0 F0 F0 F0
F008: F0 F0 F0 F0 F0 F0 F0 F0
F010: FF 27 A0 27 FF 27 A0 27
F018: FF 27 A0 27 FF 27 A0 27
F020: F0 F0 F0 F0 F0 F0 F0 F0
F028: F0 F0 F0 F0 F0 F0 F0 F0
F030: FF 27 A0 27 FF 27 A0 27
F038: FF 27 A0 27 FF 27 A0 27
F040: F0 F0 F0 F0 F0 F0 F0 F0
F048: F0 F0 F0 F0 F0 F0 F0 F0
F050: FF 27 A0 27 FF 27 A0 27
F058: FF 27 A0 27 FF 27 A0 27
F060: F0 F0 F0 F0 F0 F0 F0 F0
F068: F0 F0 F0 F0 F0 F0 F0 F0
F070: FF 27 A0 27 FF 27 A0 27
F078: FF 27 A0 27 FF 27 A0 27
F080: F0 F0 F0 F0 F0 F0 F0 F0
F088: F0 F0 F0 F0 F0 F0 F0 F0
F090: FF 27 A0 27 FF 27 A0 27
F098: FF 27 A0 27 FF 27 A0 27
F0A0: F0 F0 F0 F0 F0 F0 F0 F0
F0A8: F0 F0 F0 F0 F0 F0 F0 F0
F0B0: FF 27 A0 27 FF 27 A0 27
F0B8: FF 27 A0 27 FF 27 A0 27
F0C0: F0 F0 F0 F0 F0 F0 F0 F0
F0C8: F0 F0 F0 F0 F0 F0 F0 F0
F0D0: FF 27 A0 27 FF 27 A0 27
F0D8: FF 27 A0 27 FF 27 A0 27
F0E0: F0 F0 F0 F0 F0 F0 F0 F0
F0E8: F0 F0 F0 F0 F0 F0 F0 F0
F0F0: FF 27 A0 27 FF 27 A0 27
F0F8: FF 27 A0 27 FF 27 A0 27
F100: F1
jrsharp
 
Posts: 5
Joined: Aug Wed 19, 2009 11:04 pm

Re: Designing an Apple 1 interface card

Postby jrsharp » Oct Thu 22, 2015 12:01 pm

BTW, here is the schematic/layout for my "Apple 1 WiFi" card, for reference. It is in the very early stages of development, so there are a number of caveats:

- I'm just using the PSoC4 module/kit form factor (socketed) for convenience in testing and ease of layout for homemade PCB (good pitch and through-hole components route signals conveniently to both sides of board. This would ultimately be replaced by the PSoC4 SMD for "production".
- The ESP8266 portion is incomplete (and would again use the SMD module vs. the ESP-01 footprint)
- The schematic is very ugly. I'm still learning Upverter's schematic tool, and this was a quick-and-dirty way to get the signals laid out.

I'm attempting to embed / share the public design for this on this post. We'll see how well that works. Whatever the outcome of my experiments are, I'd like to hope that my Apple 1 card-edge connector part in Upverter is useful to other members of this community.

https://upverter.com/jrsharp/ee15e5f777f60710/Apple1_WiFi/#/Image
Attachments
File_000.jpg
Image of card in Replica 1
File_000.jpg (139.9 KiB) Viewed 15112 times
jrsharp
 
Posts: 5
Joined: Aug Wed 19, 2009 11:04 pm


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