Started in 2004 as a simple breadboard-friendly computer on Intel 8085 microprocessor...

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In June 2004 I designed very simple "computer" around Intel 8085 microprocessor (enhanced version of 8080 with a single power supply and multiplexed bus). Here I will document attempt to make a Tindie product based on this design...

Main board nedoPC-85-A v1.0 designed in 2004:

Memory map of nedoPC-85 (8 regions 8KB each):

Hex Address RangenedoPC-85-A (2004)nedoPC-85-MK (2018)
0000...1FFFROM 8KB (IC5)ROM 8KB (IC5)
2000...3FFFRAM 8KB (IC6)RAM 8KB (IC6)
4000...5FFFnot used 2nd RAM 8KB
6000...7FFFnot used External memory
8000...9FFFnot used Keyboard reading
A000...BFFFNI-15 (extension bus)NI-15 (extension bus)
C000...DFFFRAM 8KB (IC6) - copy of 2000...3FFFRAM 8KB (IC6) - copy of 2000...3FFF
E000...FFFFROM 8KB (IC5) - copy of 0000...1FFFROM 8KB (IC5) - copy of 0000...1FFF

Test board for interface NI-15 (NI = nedoInterface) that blinks LEDs:

These schematics represent test setup pictured below (2004):

In January 2018 I started working on extended version called nedoPC-85-MK that includes Cherry-MX keys and 5x7 LED matrix indicator (12 characters) plus some additional LEDs and 7-segment indicators:

  • More lights

    SHAOS16 hours ago 0 comments

    all 5x7 LED matrix installed:

    and it's working :)


    it executes this program:

       org   0
       mvi   a,0FFh
       out   0
       mvi   b,0
       mov   a,b
       out   1
       out   2
       out   3
       out   4
       out   5
       out   6
       out   7
       out   8
       out   9
       out   10
       out   11
       out   12
       inr   b
       mvi   c,9
       mvi   d,7Fh
       mov   a,d
       out   0
       mov   d,a  
       lxi   h,100
    loop2:   ; total 24
       dcx   h      ; 5
       mov   a,h    ; 5
       ora   l      ; 4
       jnz   loop2  ; 10 
       dcr   c
       jnz   loop1
       jmp   loop

  • Lights

    SHAOS6 days ago 2 comments

    And it's time to fire some lights :)

    This test eats up to 450 mA

    P.S. Still waiting for other components to finish all 12 characters of the display...

  • Cherry MX

    SHAOS03/14/2018 at 05:51 0 comments

    Here I use Cherry MX keyswitches:

    Where can I order "custom" Cherry MX caps? Handwriting doesn't look right :)

    P.S. It looks like I've just found the way:

  • nedoPC-85-MK v1.0 boards received

    SHAOS03/13/2018 at 02:14 0 comments

    Now it's time to build something cool ;)

    Unfortunately I don't have schematics for this one - I drew PCB as is (using pcb from GEDA) based on original nedoPC-85-A schematics with some thoughts from my mind regarding MK85 cloning - so the thing is I started to forget my ideas, so I think now I need to reverse-engineer my own board to re-create schematics from it...

  • nedoPC-85-MK v1.0

    SHAOS02/04/2018 at 19:27 0 comments

    This one could be a standalone 8085-based computer with Cherry-MX keyboard on board, 12 5x7 LED matrices and 6 7-segment indicators with some additional indication and stereo-audio output (2 channels with 4 bit per channel):

    Intended to resemble look of Elektronika MK-85 and CASIO FX-700P (also known as CASIO PB-100 or "RadioShack TRS-80 pocket computer"), but my board is slightly bigger (14x6") and it has more PC-like keyboard layout to make it looks like a real computer with optional backlight :)

    P.S. There is a possibility to make a true Elektronika MK-85 clone from it with help of additional board with PDP-11 compatible Soviet processor 1801VM2 (still available on ebay) with original firmware (MK-85 was PDP-11 compatible pocket computer produced from 1986 to 2000 that run BASIC interpreter similar to CASIO FX-700P)...

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Yann Guidon / YGDES wrote 6 days ago point




  Are you sure? yes | no

SHAOS wrote 6 days ago point

Wait until I connect #PDPii from behind and make Elektronika-MK85 clone out of it :)

  Are you sure? yes | no

Jasmine Brackett wrote 06/05/2017 at 16:29 point

Hey @Shaos, any updates? Are you entering this for the Hackaday Prize's "Best Product"?

  Are you sure? yes | no

SHAOS wrote 06/06/2017 at 02:29 point

may be ;)

  Are you sure? yes | no

David H Haffner Sr wrote 01/22/2017 at 14:25 point

Yes, it is true! Mark loves wire!

  Are you sure? yes | no

SHAOS wrote 01/23/2017 at 00:44 point

I love wires too, but sometimes it's too time-consuming to solder all those wires and PCB is much faster way ;)

  Are you sure? yes | no

David H Haffner Sr wrote 01/23/2017 at 08:04 point

Oh yeah, PCB is certainly faster and I love your clever design there :)

  Are you sure? yes | no

SHAOS wrote 01/24/2017 at 05:46 point

Thanks :)

  Are you sure? yes | no

Dr. Cockroach wrote 01/22/2017 at 12:28 point

I like lots of wire :-)

  Are you sure? yes | no

SHAOS wrote 01/22/2017 at 14:21 point

Finally it will be PCB for it :)

  Are you sure? yes | no

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