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Thread: ANNOUNCE: VCF East XIII 8085 Single Board Computer

  1. #41

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    Just finished building mine. This is a really nice kit. The board well designed and is clearly marked so you can almost build it without the directions.

    I did run into one odd problem with the serial clock. The oscillator is putting a clean signal into the 74HCT4040 counter, but the output has spikes that are making the baud rate 3x what it should be. See the attached traces. This is Q0, which should be clk/2. The bottom (yellow) trace is the clock input and the blue is the Q0 output.
    Q0-NewFile9.png
    At the Q1 output, it should be at clk/4, so there should be 6 edges out for every 24 in, but instead there are 18 out. Even with the asymmetric clock, it is reliable at lower rates, so if the board is jumpered for 1200 and the terminal set for 3600 it works flawlessly.
    Q1-NewFile7.png
    Does anyone who is better at hardware than me (which is everyone), have an idea of what might make it behave like this? I resoldered all of the connections to the 4040 and its bypass cap with no change. Bad chip or something else to check?

  2. #42

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    Replying to my own post with the solution from Glitch. Replacing the original 74HCT04 with a 74LS04 fixes the clock problem. The newer boards already ship with the LS part so they do not have an issue.

  3. #43

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    Folks,

    Sorry to resurrect an old thread, but did anyone else get the compact flash interface at VCFE? I brought out my board and couldn’t get it to boot into CP/M. Jonathan copies all if the relevant files to the CF card and I know I had a fully working board when I left the hacker space...

    I can get the 8085 board to boot into either GW-MON or BASIC using the RPA dipswitches.

    Anyone have a working CF interface that could tell me the switch settings on the 8085 board and cf expansion card?

    Thanks,
    Crawford

  4. #44
    Join Date
    Jun 2018
    Location
    Greensboro, NC
    Posts
    4

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    I also could never get my CF board to work right, I've been meaning to send glitch an e-mail and maybe ship the computer up to him :/

  5. #45

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    Mine is working. SW3 is:
    1 ON
    2 ON
    3 ON
    4 ON
    5 OFF
    6 OFF
    7 ON
    8 OFF

    The other main board switch (covered by the CF board) is all OFF.

    SW1 on the CF board is 4 ON, all others OFF.

  6. #46

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    Also, try settings SW3 #7 back to OFF to boot the monitor to check the version. Mine is v0.1.4.

  7. #47

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    Yaaaaa!

    It works! Thanks much, nib!

    68k, if you can’t figure anything else, I could do an image copy of my CF card. I think glitch just did ‘dd’ copy.

    -Crawford

  8. #48

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    Crawford - glad it's working!
    68km - another problem could be that your rom image doesn't have an entry to jump to the CF boot. I can help troubleshoot this if the dip switch settings don't get you going.

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