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Re: [cosmacelf] Josh's Bootstrap idea

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  • Lee Hart
    ... The Membership Card wasn t designed with the idea of making it into a full-blown big 1802 system. Small size was the main criteria, so it doesn t have an
    Message 1 of 4 , Mar 16, 2013
      On 3/16/2013 4:29 PM, William Donnelly wrote:
      > When/IF I ever get my two MC's built, one more or less OEM, and the
      > other to super-customize, I was going to make some sort of an interface
      > where you could plug multiple Altoids tins together, and all of the signals
      > you need would be there to do whatever you want. (down to TPA and B, etc.)

      The Membership Card wasn't designed with the idea of making it into a
      full-blown "big" 1802 system. Small size was the main criteria, so it
      doesn't have an expansion bus.

      However, the size lends itself well to using it as a daughter board to
      plug onto a bigger system. If you remove the 1802 and plug two 20-pin
      male-male pin headers into the 1802 socket, you can plug the Membership
      Card face-down onto your own motherboard. Between the new 1802 header
      and the 30-pin header already there, you have *all* the bus signals.

      Or, it is possible to make a new Front Panel board the same size as the
      present one. Instead of the toggle switches an individual LEDs, it can
      have the 1802 moved to it (with the headers mentioned above), along with
      whatever other circuitry you want (extra memory, UART, 1861 video, etc.)

      Similarly you could use the 40-pin 1802 socket as your "bus" to add as
      many cards as desired. Each card could even be in its own Altoids tin. :-)

      > I wanted to go left/right, top/bottom, so it's not just one long string
      > of tins

      Running a bus left/right/top/bottom is going to be a challenging PCB
      layout. You'd have 40-plus traces connecting all 4 edges! Virtually all
      the space on the board would be taken up by these traces, leaving very
      little for the circuitry itself.

      I guess you could have a 4-way bus board that has nothing else on it but
      the 4 bus connectors, and a 5th one in the middle. The Membership Card
      (or other cards) plug into this center connector.

      > Cutting the tins for the connector holes might not be easy.

      Yes indeed. That thin steel is difficult to cut cleanly. That's why I
      added the Cover Card -- to save that precision metalworking. Altoids
      tins are cheap (about $2 with the mints). That's cheaper than buying a
      *real* case of some kind! But it's not as easy to work with as plastic
      or aluminum.

      > You could put a hex keypad on/in an Altoids tin. It would be pretty
      > small, but probably very usable, depending on what key switches you

      I am working on exactly that! The plan is a 2-digit hex LED display
      instead of the individual LEDs, and a little 16-key keypad. The board
      would also have an EPROM socket, and a serial interface for a cassette /
      sound card / RS-232, or TTL serial via a USB-to-TTL serial adapter.

      Ingenuity gets you through times of no money better than money
      will get you through times of no ingenuity. -- Terry Pratchett
      Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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