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Re: cheapest way to provide a 80x24 display

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  • rileym65
    I agree here, just use vt100 codes, most terminal software understands them and using them can give you a fully addressable screen. I have used the vt100 codes
    Message 1 of 7 , Mar 31, 2009
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      I agree here, just use vt100 codes, most terminal software understands them and using them can give you a fully addressable screen.

      I have used the vt100 codes within my Rc/Basic and Elf/OS software quite effectively.

      The beauty of this solution is that it is simple, pc-side software already exists and a serial port is easy to add to an 1802. For the purists out there, this at least keeps the 1802 side of things as vintage as they like, afterall, rs232 existed back then and so did serial terminals.

      Mike

      --- In cosmacelf@yahoogroups.com, "randy129" <randy129@...> wrote:
      >
      > --- In the thread "HP 5082-7340 Displays on eBay", Patrick Draper wrote:
      >
      > > But what is the cheapest way to provide a 80x24 character
      > > display on a small 1802 based computer?
      >
      > A terminal program on your PC. Cheapest and easiest.
      >
      > > I am not making any plans to build one right now, I was just
      > > brainstorming it.
      > >
      > > Certainly, I could make a serial interface to a terminal running
      > > on the PC. But why not make that USB instead? Immediately, a USB
      > > microcontroller comes to mind as a cheap solution.
      >
      > What comes to my mind is one of those USB to serial adapters.
      > I have never used one, but I know a lot of people use them
      > with winavr to download from their notebook to AVR micros.
      >
      > I see one on ebay, $3.50 "buy it now", including shipping.
      >
      > > But then if I have a USB microcontroller why not use
      > > it to make the programming interface easier?
      >
      > By that same reasoning, why not use the USB micro to
      > implement the 1802, and ram, and any other logic?
      >
      > I started out to see if I could fit a two digit
      > display into an AVR (like Mark G. did for one),
      > and I ended up with an entire Elf inside an Atmel Butterfly!
      > It's a rather slippery slope! :-)
      >
      > > Why not make the
      > > display memory mapped rather than TTY based (and all the
      > > complexity that comes from terminal handling).
      >
      > What is so complex about terminal?
      >
      > However you implement it on the elf side, you will need
      > to use some protocol over the cable. vt100 might be a good
      > choice. Then you don't need custom software on the PC side!
      >
      > Now suppose you have an AVR on you elf, it appears as a
      > block of ram to the 1802, and whenever a char is written
      > to this "RAM", the AVR will have to send something to the
      > PC over the USB cable. Hmmmm... It will need to let the
      > pc know the row/col, and the new character, unless you
      > mean to send the whole screen every now and then.
      >
      > Either way, vt100 seems like a good protocol.
      >
      > Now suppose you want to scroll the screen. The elf
      > will need to block move a big chunk of this "RAM"
      > that lives in the AVR. And the avr will have to send
      > the "new" screen. It could work, but I don't know
      > that I would call it an elegant solution. I am
      > wondering what would be so bad with letting the
      > 1802 send the vt100 commands directly?
      >
      > > Is is really easier to provide an 80x24 character
      > > display some other way?
      >
      > It is certainly easier in the sense that the other
      > way already exists! (At least for the 80x24 text).
      >
      > Now simulating the 1861 is another story. There
      > are programs that expect a memory mapped display.
      > But I wonder if you couldn't still use a terminal
      > on the PC end with a custom font??? Can terminal
      > progs display the vga graphic chars???
      >
      > > I know this is a hack. But I don't think it's any more
      > > unreasonable than building a serial port and using a
      > > terminal program running on a PC as a display.
      > >
      > > Or is it?
      >
      > I guess that would depend on your own definition
      > of "more unreasonable". :-) :-) :-)
      >
      > As long as you are learning, or just having fun,
      > and not blowing yourself (or anyone else) up,
      > who's to say it's unreasonable?
      >
      > Randy
      >
    • Chris Elmquist
      Apologies if this one was already discussed-- but I don t remember seeing it: http://www.brielcomputers.com/wik/index.php?title=PockeTerm I just ordered one
      Message 2 of 7 , Apr 5, 2009
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        Apologies if this one was already discussed-- but I don't remember
        seeing it:

        http://www.brielcomputers.com/wik/index.php?title=PockeTerm

        I just ordered one to play with. No other affiliation expressed or implied :-)

        Chris
      • Andy Valencia
        ... I was wondering about mentioning this kit again (it was mentioned on this group a while back). I bought a couple and like the hardware very much. I
        Message 3 of 7 , Apr 6, 2009
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          --- In cosmacelf@yahoogroups.com, Chris Elmquist <chrise@...> wrote:
          >
          > http://www.brielcomputers.com/wik/index.php?title=PockeTerm
          > I just ordered one to play with. No other affiliation expressed or implied :-)

          I was wondering about mentioning this kit again (it was mentioned on this group a while back). I bought a couple and like the hardware very much. I wanted a more ANSI-centric feature set, and since it's open source I was able to cook up alternate firmware:

          http://www.vsta.org/ajvTerm/

          It's pretty neat to work with a chip with 8 parallel CPU's. Instead of using UART's and VGA display chips, they instead can dedicate CPU's to the time-critical tasks of wiggling output lines and decoding input lines.

          Andy
        • Robert L. Doerr
          I have an old video board that uses an old set of terminal chips for the display. It has two 40-pin DIP chips that I haven t seen before. They are SCN2673
          Message 4 of 7 , Apr 8, 2009
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            I have an old video board that uses an old set of terminal chips for the
            display. It has two 40-pin DIP chips that I haven't seen before. They
            are SCN2673 and SCN2674 terminal display chips. Does anyone here have a
            datasheet for them or have a spare SCN2673 they would be willing to spare?

            Robert
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