• RetroShield for Arduino

    From Jeff@21:1/180 to All on Mon Jan 10 09:48:38 2022
    Hi all,

    8bitforce.com created some PCB designs for several variations of their RetroShield, which is a shield for the Arduino Mega (or pin-wise equivalent) allowing it to interface with various 8-bit microprocessors. The Arduino is then responsible for driving the microprocessor's clock, servicing memory requests, etc., providing a cheap, easy way to explore the workings of these processors.

    I received the 6502 and Z80 variations in a subscription box (no longer available) and decided to order more*, plus a variation for the RCA 1802 microprocessor. I had to buy in multiples of 5, and 10 costs the same as 5,
    so I ordered 10 of each: 6502, Z80, and 1802. The total cost was $35.99, $24
    of which was shipping.

    I ordered from NextPCB.com and submitted the gerber files located here: https://gitlab.com/8bitforce/retroshield-hw/-/tree/master/manufacturing (the gerber files are in a zip file within each processor-specific directory).

    I'll let you know how the final boards turn out, if anyone is interested in doing the same. Assembly of the boards does require acquiring and soldering a few smd components (resistors and capacitors), as well as a processor-appropriate socket (if desired), an LED, an 18x2 male header, and
    of course a processor chip.

    More info on the boards can be found here: http://www.8bitforce.com/projects/retroshield/

    Jeff.

    * The 6502 and Z80 chips that came with the kit were vintage chips pulled
    from who-knows-where. The 6502 board has a pair of solder pads that need to
    be bridged for older chips, but left unbridged for modern 6502s. Since the
    chip I had was an older one, I bridged them. However, the modern chips are better in a number of respects (including being more tolerant of Silly User Mistakes) so I'd like to use that. I also have a few spare 1802s since I had
    to buy 5 to get the 1 I needed for another project. So that's how I came to order 30 PCBs.

    --- Mystic BBS v1.12 A46 2020/08/26 (Raspberry Pi/32)
    * Origin: Cold War Computing BBS (21:1/180)
  • From Jeff@21:1/180 to Jeff on Sat Jan 22 11:10:09 2022
    On 10 Jan 2022, Jeff said the following...
    I ordered from NextPCB.com and submitted the gerber files located here: https://gitlab.com/8bitforce/retroshield-hw/-/tree/master/manufacturing (the gerber files are in a zip file within each processor-specific directory).

    I'll let you know how the final boards turn out, if anyone is interested in doing the same. Assembly of the boards does require acquiring and soldering a few smd components (resistors and capacitors), as well as a processor-appropriate socket (if desired), an LED, an 18x2 male header, and of course a processor chip.

    The PCBs arrived and I assembled one of the 1802 (COSMAC) boards. It successfully runs at about 100kHz driven by an Arduino Mega. Since the 1802 requires 8 clock cycles for each machine cycle, and most instructions take
    1-2 machine cycles, this works out to about 8000 instructions per second.

    The 1802 is a very unique chip, a significantly different approach to an
    8-bit microprocessor than the 6502, Z80, etc.

    Jeff.

    --- Mystic BBS v1.12 A46 2020/08/26 (Raspberry Pi/32)
    * Origin: Cold War Computing BBS (21:1/180)
  • From Fr333n3rgy@21:1/136 to Jeff on Sun Jan 23 22:16:26 2022
    Re: RetroShield for Arduino
    By: Jeff to All on Mon Jan 10 2022 09:48 am

    so I ordered 10 of each: 6502, Z80, and 1802. The total cost was $35.99, $24

    Hey Jeff, where did you order the Z80s from? I was looking for a reliable source for a single-board computere project I was going to do for my kid to teach him what goes in inside a computer (kind of) ...
    --- SBBSecho 3.14-Linux
    * Origin: The Oracle BBS - theoraclebbs.com (21:1/136)
  • From Jeff@21:1/180 to Fr333n3rgy on Sun Jan 23 21:49:15 2022
    On 23 Jan 2022, Fr333n3rgy said the following...
    so I ordered 10 of each: 6502, Z80, and 1802. The total cost was $35.99
    Hey Jeff, where did you order the Z80s from? I was looking for a reliable source for a single-board computere project I was going to do for my kid to teach him what goes in inside a computer (kind of) ...

    In that particular instance, I was referring to PCBs for use with Z80s, but
    as far as the Z80s themselves... Digikey has several different varieties (https://www.digikey.com/en/products/detail/zilog/Z84C0010PEG/929206 for example) as does Jameco (https://www.jameco.com/z/Z80-CPU-Major-Brands-IC-Z80-CMOS-CPU-2-5MHz-DIP-40-pi n_35561.html for example).

    Jeff.

    --- Mystic BBS v1.12 A46 2020/08/26 (Raspberry Pi/32)
    * Origin: Cold War Computing BBS (21:1/180)