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Thread: Floppy drive noise question...

  1. #1

    Default Floppy drive noise question...

    I'm working on making a Epson PX-8 floppy drive emulator (TF-15). I've got a piezo and can make various frequencies and lengths. I've been listening to various floppy drive noises like this one:

    https://freesound.org/people/MrAural...sounds/259292/

    I downloaded this and looked at it in a WAV viewer and it looks like the original noise is pretty long as in over 300 milliseconds.

    Then there are shorter 25ms noises that I am presuming that are each a track increment as it is reading.

    Question # 1 - is the original 300ms noise really just it moving the heads all the way across the disk as in perhaps all 40 tracks?

    Question # 2 - assuming Q#1 is yes, if it moved 20 tracks and not 40 say, would it have been 150 milliseconds long?

    Question # 3 - looking at the waveforms for these sounds, they are complicated, which I am not going to reproduce in an 8 bit microcontroller/piezo combination. Really I'm just trying to make it sound somewhat like it did to give the user an audio feedback of disk access. I measured frequency content where it was measurable at around 1250 Hz which is crazy high. My best sound so far has been running the frequency really low like 75 Hz.

  2. #2

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    Well...after some experimentation with it, the best thing is to just make it start out with a longer noise and then repeat a smaller noise every so often like 700ms. This keeps it from getting too noisy when CP/M is reading all the directory sectors for example.

    The TF-15 emulator is coming along quite nice. Display working, piezo working, epsp protocol working, read/write/reset/flush/copy/format all tested and working. Right now I've got it mounting d.img, e.img, f.img, g.img because I don't have the UI working yet. Next up is implementing the user interface so you can dismount disks and then select them from a sorted menu. It will have the ability to add/remove write protection per drive, it should be able to emulate one or two TF-15's, either DE, FG, or DEFG. I *think* it should also work along side a real PF-10 or TF-15 if it is at the end of the chain. I hope to make the UI add/rename/delete disk images on the microsd.

  3. #3
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    I'm forced to admit that this is the first time in my experience that someone has asked for floppy noise to simulate. What's next? Simulation of a high-speed train printer with an open cover? An industrial dot-matrix printer? A bank of 24 half-inch tape drives with all vacuum pumps running? A high-speed card punch?

    After years of wearing earplugs in the computer room, I'd have to say that the only good computer is a silent computer. Even fan noise bugs me now.

  4. #4

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    I do remember the screeeeeech and noise of printers... It will have an option to disable the sound for those who prefer silence. For me I just can't trust a "floppy drive" that doesn't make some noise, even if it is virtual...

  5. #5

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    Quote Originally Posted by Chuck(G) View Post
    I'm forced to admit that this is the first time in my experience that someone has asked for floppy noise to simulate.
    I have to admit, I did miss the sound of a 5 1/4” floppy from my PC clone. I was actually quite disappointed with my compaq portable (one of the first vintage computers I collected, recently). The floppy drives in it are almost silent. It actually made me wonder if all of the old drives I’d owned back in day were in need of maintenance.

  6. #6
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    Some folks look back with nostalgia on the old days, but not me.

    I don't miss changing 14' wide printer ribbons and getting ink all over a clean shirt. I don't miss slipping in a pool of oil from a leaking disk drive. I don't miss tripping while carrying a tray of cards, scattering them all over the floor. (think about the poor schlub who left his cards on top of the 1403 printer when it ran out of paper). I don't miss the high-speed card reader catching a corner of a card and mangling and accordion-pleating the next 5. I don't miss the noise. And I'm still amazed at the utter reliability of hardware nowadays.

  7. #7

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    One way to avoid having to analyze and reproduce the noises as a facsimile of the original thing, would be to use a microphone to record an actual drive working, on a small audio recorder IC, then you can just activate that IC, feeding a small speaker or transducer to "play" when the drive emulator is active.

  8. #8

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    I was somewhat trying a cheaper version of that Hugo - I don't want to add any additional parts that aren't necessary to the design, so in my case I've got a piezo and two microcontroller pins to generate a frequency on. I can keep one pin ground and toggle the other pin for half volume or toggle them both against each other for full volume. Piezo's aren't great for frequency or sound reproduction as I think certain frequencies are much louder than others, but use very little current which is great. My thought was, if I could see what the actual sound looked like, perhaps I could try to copy it poorly. The duration's were fine, but the original sound is too complicated in its frequency content for me to try to boil it down to a single frequency (which isn't surprising...).

  9. #9
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    I'm not following your logic. Surely, if you can maintain the appropriate bitrate, you can approximate what you need using the PWM capability of your MCU (most relatively modern ones have that built-in).

  10. #10

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    I'm just setting a frequency and duration - not actually trying to play back any sort of recorded pattern at a bit rate. I'm not sure even if I could produce it that a piezo would be able to reproduce the sound. Some AVR's have DMA and would be better suited.

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