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Thread: WTB: CI-7 cassette interface cable for the TI-74 BasiCalc

  1. #1
    Join Date
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    Default WTB: CI-7 cassette interface cable for the TI-74 BasiCalc

    I recently posted a request in the Wanted section:

    http://www.vcfed.org/forum/showthrea...TI-74-BasiCalc

    Does anyone have the schematic for the CI-7 cable?

    Thanks!

    smp

  2. #2

    Default

    I'm wondering if we could easily make one.

    Jim Brain has been helping us out with CC-40 peripherals lately. The 74 has the cassette stuff mostly built in.

    Some folks on Stack exchange got a rudimentary interface going: https://electronics.stackexchange.co...lculator-ti-74
    Here's what the innards of the cassette interface looks like: http://www.datamath.org/Graphing/JPEG_CI-7.htm#PCB
    YouTube video of what the cassette signal sounded like: https://www.youtube.com/watch?v=q_Tu...ature=youtu.be

    Note that the interface is just a 74HC367 (3 state hex line buffer/line driver), a CA358E (Op Amp), and a bunch of caps, resistors, and transistors.

    "Paolo" on the Stack Exchange discussion was on the right track for a home-brew adapter: http://www.datamath.org/Graphing/JPEG_CI-7.htm#PCB

    ------ clip ------
    I realized such an Interface severals years ago. The "Data Output" pin is pin #6 --> D3. The "Data Input" pin is pin#3 --> D0.

    Recording:

    you are on the right way: just use a voltage divider (e.g. 2 resisitors) to match the voltage requirements your recorder. A 100nF capacitor between voltage divider and mic-input could help.

    Playback:

    You have to clean and amplify the recorded signal, it must be a square wave, with low state = "GND" and high state = "VCC".

    I used a common LM358N as non inverting Schmitt-Trigger to obtain a clean wave. It'easy, you need only 4 resistors. I played wit several resistor values, I obtained the best results with a 0,3V treshold.

    You can supply the LM358N from Pin#1. Ok, it drains power, but not noticeably

    I used the same interface with a Sharp PC-1260: VCC: pin#2, GND; pin#3, data in: pin#6, data out: pin#7

    Have fun!

    Paolo
    ------ clip ------

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