Directly connecting the Raspberry Pi Pico to the Apple II slot bus

[Oliver Schmidt]

Hi,

I wanted to let you know that it actually is feasible to directly
connect the Raspberry Pi Pico to the Apple II slot bus. Today I
published my Pico source code that makes this possible:

https://github.com/a2retrosystems/A2retroNET

Regards,
Oliver

[Anthony Ortiz]

Oliver, good stuff man! I've been on the comp.sys.apple2 group and didn't see this post. I never worked on the Pico but about 5 years ago I was fooling around with my PI 3 and made it so that I could read/write to the Apple II bus via GPIO bit-banging. Back then I only used 8 pins for the bus so I had to push the LO and HI address bytes as well as the data bytes separately into some flip-flops, but recently I've revisited the project and I'm in the middle of simplifying it to an FPGA, but I think I'm going to go with the Max V CPLD instead. What are your plans for the Pico?

[Oliver Schmidt]

Hi Anthony,

>Oliver, good stuff man!

Thanks for the positive feedback :-)

>What are your plans for the Pico?

One usecase is using the RPi Pico to connect an "ordinary" RPi to the
A2. Instead of fiddling with RPi GPIO, you just use a USB cable. The
simplest USB setup is to have the RPi Pico act as USB device
implementing a virtual serial port (following the ACM CDC
specification). The "ordinary" RPi acts as USB master, that
automatically loads its ACM CDC driver offering a /dev/ttyACMn port.

I've taken the two exsisting well-known "connect an RPi to the A2"
projects and applied that approach to them:

https://github.com/oliverschmidt/Apple2-IO-RPi
https://github.com/oliverschmidt/apple2pi

They now both work nicely with my Pico-based prototype card - incl.
their firmware ROM being emulated by the Pico :-)

There are of course many other usecases, either emulating other
existing A2 cards or inventing totally new ones. We'll see ;-)

Regards,
Oliver