[HN Gopher] Open Source FPGA Expansion Card for the Apple II
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       Open Source FPGA Expansion Card for the Apple II
        
       Author : tjake
       Score  : 95 points
       Date   : 2024-08-13 16:57 UTC (3 days ago)
        
 (HTM) web link (wiki.reactivemicro.com)
 (TXT) w3m dump (wiki.reactivemicro.com)
        
       | tjake wrote:
       | YouTube interview with creators:
       | https://www.youtube.com/watch?v=gJXZZJZc5gI
        
       | edanuff wrote:
       | GitHub repo here - https://github.com/a2fpga/a2fpga_core/
        
       | _Microft wrote:
       | If you are as curious as I were what the card looks like, then
       | have a look at this:
       | 
       | https://github.com/a2fpga/a2fpga_core/blob/main/boards/a2n20...
       | 
       | I always find it impressive how integrated our electronics have
       | become and how few components are required to achieve what would
       | have taken large, crowded PCBs in the past.
        
         | edanuff wrote:
         | Project co-creator here - that's actually the V1 board, the V2
         | board is here
         | https://github.com/a2fpga/a2fpga_core/blob/main/boards/a2n20...
         | and uses a slightly larger CPLD (complex programmable logic
         | device) which is what's used to map and level shift the 5V
         | signals from the Apple II bus to the 3.3V pins on the FPGA
         | module. We use the Sipeed Tang Nano 20K FPGA module for the
         | FPGA. Using a pre-built module like this is a great accelerator
         | in this type of project because a lot of the more complicated
         | things to get right, like the power supplies or the length of
         | the traces for the HDMI connector, are done for you.
        
           | robinsonb5 wrote:
           | Very cool project - I'd be all over this if I was lucky
           | enough to own an Apple II!
           | 
           | (I think there's a typo in the credits section of the github
           | Readme: you have alanswx listed as Alex Steremberg instead of
           | Alan?)
        
             | edanuff wrote:
             | Yup, definitely Alan not Alex! Alan has been the person who
             | has brought a lot of attention to the Apple II core in the
             | Mister FPGA platform.
        
         | I_AM_A_SMURF wrote:
         | Yep. I've been looking at an old arcade board's design for fun
         | lately, and it's a lot of giant (for today's standards) DIP
         | chips that are just flip-flops, and gates, or gates, which
         | modern cheap FPGAs have by the tens or hundreds of thousands in
         | them.
        
       | klyrs wrote:
       | If you program the FPGA with an Apple ][ emulator, can we call it
       | a HyperCard?
        
       | woodrowbarlow wrote:
       | once again i regret my decision to get an apple //c for my
       | collection rather than the more expandable apple ][ or //e. in my
       | defense, it just looks so cute!
        
       | distantsounds wrote:
       | 720x480 is not 720p, that's 480p (assuming progressive scan and
       | not interlaced).
        
         | edanuff wrote:
         | Good catch, that's a mistake that's now been corrected, it's
         | definitely 480p. The Github page
         | (https://github.com/a2fpga/a2fpga_core) had it correctly.
        
       | zellyn wrote:
       | This is fantastic. I once dreamed of making a generic interface
       | card that could be programmed at will, using, say, a raspberry
       | pi. However, a look through the timing diagrams in Sather shows
       | surprisingly tiny latencies between the address and r/w signals
       | hitting the bus, and the memory value needing to be presented. I
       | concluded that an fpga would probably be required. Always fun
       | when you can wait a few years and someone smarter than you builds
       | the thing you imagined!
        
         | edanuff wrote:
         | Project co-creator here - This was something I'd wanted to do
         | since I first started playing with FPGAs 20 years ago but the
         | idea was resurrected during the pandemic. It's definitely
         | easier with an FPGA but there are other projects that interface
         | an ESP32 or RP2040 to the Apple II bus. The FPGA approach
         | allows you to architect your logic in ways that are much closer
         | aligned to the original hardware design and in many cases, you
         | can directly translate Sather's logic diagrams to Verilog code.
         | BTW, Sather's book has recently been reissued:
         | https://www.callapple.org/books-3/understanding-the-apple-ii...
        
       | djfergus wrote:
       | Great to see the Sipeed Tang Nano modules being used - they are
       | based on a Gowin FPGA chip and the dev modules (with HDMI and a
       | stack of GPIO pins broken out) cost peanuts on aliexpress
       | compared to equivalent FPGAs from more popular vendors. The
       | vendor IDE is usable and open source tools are improving.
       | Exciting times for embedded hobbyists.
        
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       (page generated 2024-08-16 23:02 UTC)