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6562Re: [cosmacelf] Re: Membership Card - Ultra Low Power Variant

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  • Lee Hart
    Mar 1, 2010
      aa3nm wrote:
      > My goal is to have a truly minimum power ELF that is as simple as
      > possible with binary input and output. That being said, the tedium
      > of programming anything more than ~50 bytes gets old very fast, even
      > with toggle switches (been there too).

      Yep; me too! But, it's a heck of a lot less painful with good switches.
      Use the best, easiest-to-use switches you can find. Notice that many of
      the traditional minicomputer front panels and organs use piano key like
      paddle switches.

      Same for a display. 8 raw binary LEDs are simple and cheap, but have few
      other attributes. The LCD display is lower power, and can produce a much
      nicer display.

      The small step up to a hex keypad and hex display is a big improvement
      over binary.

      You might also consider adding a circuit so a PC's parallel port can
      manipulate the front panel switches, as a way to automate the
      downloading process.

      Other thoughts: I don't think nearly enough creativity has been applied
      to the data entry and display issue. People quickly fixate on the
      antique QWERTY keyboard and video text displays. They work , but it
      takes a *lot* of hardware and software to support them.

      How about some of these alternative, just for fun... :-)

      - Morse code. A single switch contact is all you need for input.
      One bit to drive a speaker is all you need for output.
      The software to read and write Morse code is trivial (ham radio
      operators have written it many times, so examples are plentiful).
      Morse code (especially for numbers) isn't very hard to learn.

      - Voice. Pick 16 audio tones to represent each hex digit 0-F. Whistle
      or hum them to input data. A microphone and simple hardware/software
      interprets the tones. Play the same tones back to read the data.
      Has the advantage that it can also be saved and loaded with a tape
      recorder or PC sound card. You "sing" to your computer, and it "sings"
      back to you, like R2D2.

      - Calculator. A calculator has special keys for each function; + - /
      sin, square, etc. So, have keys labelled PHI GLO BR etc. and an
      alphanumeric display that shows assembler mnemonics.

      - Graphics and light pen. The display is a printed drawing of the 1802
      architecture, with a single LED at each register, and perhaps 24 LEDs
      showing the current memory address and its contents. A light pen
      (just a phototransistor in an old pen body) connects to an EFx line.
      Poke LEDs to turn them on/off, or move data to/from registers I/O
      and memory. The LEDs are multiplexed, so the time at which the light
      pen sees the pulse of light tells it which LED you pointed at.

      - Mouse with a view. House the ELF in an old computer mouse case.
      Attach a little plexiglass window that has an LED/LCD display.
      Set the mouse on a printed drawing of the computer architecture.
      As you move the mouse over a box on the drawing, the display on the
      mouse shows you the contents of that box. Aim at Register A, and it
      displays the contents of RA. Needs a mouse that doesn't "slip", or
      is reading codes printed on the page to know where it is. Use the
      mouse buttons to increment, decrement, scroll wheel for faster
      up/down changes, or to drag data from one register to another.

      - Analog meters and pots (a steampunk Elf). A pair of analog meters
      are marked 0 to 15v. A simple D/A converter converts the two hex
      digits you get from a typical Elf into two voltages ("A4" displays
      as 10v on the left meter, 4v on the right meter). Two pots or
      rotary switches under the meters are similarly labelled 0-15v.
      Use knife switches for the load/run switches.

      > BTW, I know you did a lot of work on the power consumption of the
      > membership card - Do you have any sense on the consumption of this
      > layout? I read on Herb's page that you were "running air" on the
      > membershiip card overnight from the charge in the .047 uF cap, but
      > adding the LCD display bumps up the power consumption (a lot less
      > than LEDs but its still there).

      LCDs vary a lot. The older simpler ones (no backlight, no color, not
      multiplexed) are very low. The Lumex display on the LCD Elf I posted
      will probably run on less than 10 ua.

      Pullup resistors and memory chips are likely to be your the biggest
      problems. You need a design that avoids pullup resistors. The old 5101
      chips I used are true CMOS; zero power consumption when all inputs are
      static. but almost all modern RAMs (even those claimed to be CMOS) draw
      a significant supply current when chip selected even if all inputs are
      Lee A. Hart | Ring the bells that still can ring
      814 8th Ave N | Forget the perfect offering
      Sartell MN 56377 | There is a crack in everything
      leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
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