Quiet here, innit?

Home Forums Z80 Playground Early-Adopters Quiet here, innit?

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    Off topic but whilst its quiet on the Playground front, hopefully these recent projects are of some interest…

    I’ve recently built a Cosmac Elf which is a trad toggleswitch-&-LED computer from Popular Electronics in August 1976:

    …and designed an auto-keyer for it:
    https://www.youtube.com/watch?v=r2wg1XRENAg , later adding a hex keypad using the same hardware:

    This morning I just received the second batch of the PCBs I did for Karen Orton’s PICL NIBL computer:

    ‘Kitbug’ was the original SC/MP monitor rom, I’ve found a reasonable scamp assembler and I’ve been updating my own ‘KitbugPlus’ in my homebrew SC/MP with all the hand-coded extensions that never made it into a source file – its working great!

    Finished spraying the SWTPC 6800 reproduction case, but its chipping so easily it needs sanding off and starting again, this time with proper preparation. The 6800 board is working great, I have selectable Mikbug, SWTbug and a much improved homebrew monitor for it.

    I’ve also wasted a couple of evenings looking for a copy of “Stairway” that I coded for Richard Russell’s CP/M music compiler – to no avail – its long lost 🙂 My last hope is that somewhere I’ve a really, really old box of print-outs. Maybe. 🙂

    Whats everyone else been up to in the workshop?



    I’ve been playing with using your PIO board to interface to a 4×20 alphanumeric display.

    Alphanumeric display

    I have some basic driver routines written and I am going to improve them when I get round to it.



    I’m back on my 6502 project, need to get the prototype to a point where I can think about getting some PCBs made up. Assembling the playground has clarified a few things for me, but also given me a lot more to think about!


    >>I’ve been playing with using your PIO board to interface
    >>to a 4×20 alphanumeric display.

    Looks like the forum is being weird about photos again, I had to right-click, open in a new tab to see your pic 🙂
    That looks good John crisp & clear display – you most likely know that the 8 data lines can be 4? you still need RS and E so 7 lines including ground. 8 if you need to read the display (I always ground R/W) 🙂 Nice!

    Rob – I never did any 6502, never had a 6502 machine so thats an area I missed out on completely… IIRC John (Playground John) was doing a 6502 in TTL !!!



    you most likely know that the 8 data lines can be 4?

    Yeah, but there are more than enough ports to use 8 data lines and I want to be able to read the buffer flag and display address. So it is easier to use 8 bit mode. I am using ports A/CU in mode 0 (A status input/data ouput and CU E/RW/RS ouput), leaving B/CL for further development in mode(s) to be decided.



    Sorry about the block quote being so large! I didn’t expect that!


    I just finished installing my Z80-PG in a (nice) wooden box. It works perfectly!
    It’s supply under 12..21V with a buck converter DC-DC
    I will make the front face with a laser printer and Kicad !

    My future projects are :
    Add some functions to the monitor part of cpm.asm
    — read the intel-hex file and run it
    — integrate the Xmodem protocol in receiving and sending
    — goto / run to an address
    — enter hex code directly to an address
    — adapt the Intel SDK85 monitor in a .COM file
    — and anything else I can think of :-))
    For my use, I remove some parts : Burning test, TinyBas, GOFL and Test-Uart

    I bought some devices on Ebay to start a new “Z80-PG” with a
    TMPZ84C015BF10 .
    This is a chip with Z80, SIO, PIO, CTC and clock generator integrated in a 100 pin flatpack.
    Lots of small pins but less wiring for the other circuits.

    But for now, I read every line of assembly code of cpm.asm, Bdos.asm and Bios.asm .
    I want to understand in detail how all the routines work.
    This will keep me busy for a while, I think .

    Translated with http://www.DeepL.com/Translator (free version)

    • This reply was modified 5 months, 3 weeks ago by Kotec53.

    I’m sorry to report that I’ve done nothing of interest for a couple of months. This time of year, when it’s mostly dry, and it’s light at night, I’m usually working in my woods. Unfortunately, I haven’t even been doing that recently, because I’ve had Covid along with the rest of my family. Although I’m over the acute phase of the disease, I’m some way from being able to say I’m recovered. I don’t seem to have the energy to do much of anything at present.

    I continue to look at this forum, to marvel at the amazing things that other folks are doing 🙂 With luck I’ll have my soldering iron out again in the autumn.



    Sorry to hear you have been affected by Covid. If you have time on your hands, why not brush up on your Z80 programming skills. It’s always good to keep your grey matter busy 🙂

    Take care



    Been really inactive due to summer vacation and betwen jobs.
    Got the 8255 board from Phil and it is super cool. been using Raspbery Pi a lot and then you are spoiled how simple it is to connect sensors via i2c oct 1- wire protocols. Any ideas how to connects a bmp085 sensor to the z80 playground. I guess that there must be code floating around for 1- wire protocols etc

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