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Thread: Teensy I/O Processor for a Vintage Sharp

  1. #1
    Junior Member psmart's Avatar
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    Teensy I/O Processor for a Vintage Sharp

    Hi All,

    Joined up to share a use of the Teensy 3.5 for interested people.

    Basically I have created a daughter board (a few designs but 2 stable, 1 discrete logic based, 1 CPLD based) to relocate a Z80 processor in Sharp MZ series computers (but could equally well go in any Z80 computer) and act as the I/O processor and provide SD card services, real time in-situ monitoring and debugging and ability through detection and interception of making the host appear to be another machine.

    The project is at https://eaw.app/sharpmz-upgrades-tranzputer-sw/ if anyone is interested, the source code in github at https://github.com/pdsmart/tranZPUte...aster/software and https://github.com/pdsmart/zSoft . Feel free to use any code if it helps your projects.

    The Teensy 3.5 is great, the only complaint I have about it is assembly when using the underside pads, I've wasted a few boards trying to assemble them as my design needs most of the I/O.

    Phil.

  2. #2
    Junior Member psmart's Avatar
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    Just to elaborate on the assembly issues, the following photos are what I found works best. I have tried contact soldering (no pins) and wasted a Teensy, have also tried rigid pin and thicker (1/4w resistor) wire and the pads peel off. In the photos I'm using 1/8w resistor leads with the outer casing of 2.54mm header pins and this seems reliable but a bit fidgety assembling. Wire wrap wire is probably the best but a pain to strip hence not using it!

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  3. #3
    Senior Member+ defragster's Avatar
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    Good you made it work - hopefully the under pin leads stay well connected.

    In this image lower left edge you can see dual row SMD pins. They are a bit tight - but supporting them in place to solder some pins in holding it works. Then they can be socketed or direct soldered.



    That from TallDog ... tindie.com/products/loglow/teensy-3536-breakout-revision-a-dip-64/

  4. #4
    Junior Member psmart's Avatar
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    Thanks for the feedback, good to know about your kit for future dev projects. Your kit does look excellent, good way to break out the additional pads. I tried several methods including SMD and I then used needle pins manually soldered in to make contact with the pads, but in that particular case, the K64F was either bad or something went awol as the K64F refused to output anything to any of its pins, functionally and programmatically it was fine, even for input, just outputs failed.

    My projects are not commercial, I may make a board or two if any Sharp enthusiasts asks, but not for profit. Given my failure ratio with the Teensy 3.5 (good for Paul's bottom line but it also wastes pricey components as the board is scrap) and the low profile restrictions I have on future boards, Im going to transpose Paul's schematic onto my boards and buy the boot MPU from him (I have 4 on wasted boards already I could reuse!!!).

    Below is a photo of 4 versions in the same project where I got the Teensy to play ball, some tracks were damaged but on the first two designs I used pin+socket on all pins including pads so was easyish to remove and correct, later designs the board is soldered in and if it was bad, the board was scrap!

    Click image for larger version. 

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