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Topic: VHS Data storage (Read 13 times) previous topic - next topic


Yep this is definitely viable for Arduino.  You are right about the normal audio tape heads cant practically read or write a "1" or "0" directly.  But the cassette deck takes care of all the details when recording audio.  So make data into audio.

Back when the earth was cooling, small microcomputers began to scamper about beneath the feet of the big mainframe dinosaurs.  A floppy disk drive cost over $1000 and we could only dream of someday owning a hard disk with 0.0001 GB capacity.  We used a standards called "Kansas City" or "Tarbell" see http://en.wikipedia.org/wiki/Kansas_City_standard  

Something like this would still be the easiest way to use magnetic tape today.

James C4S

Funny this came up.  Today I was at Goodwill and bought a small tape recorder for $4.  My intent was to take it apart for the motors, headphone jack, and other fun parts.  (The AA batteries have a decent charge on them even.)

I didn't give it serious thought, but I wondered what would be involved in re-creating a C64-era data-casette drive.
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Jan 24, 2011, 06:07 am Last Edit: Jan 24, 2011, 06:09 am by Osgeld Reason: 1
I have  a doo-hicky that plugs into a pc parallel port and saves data to a VHS recorder. It holds ~ 120MB dos formatted on a SP tape

I have no real idea how it works but it appears that its storing it in a appropriate video grid of 1/0 bits as black or white, with aduio noise (checksum?)

I bought it for < 20 bucks in the late 90's new and failed at the swap meet, point is its not impossible (its just a video barcode, though reading it would be near impossible without, and a real SOB with some external hardware)


If you want to go the audio cassete way, the best method is bi-phase data encoding, which is what the "Kansas City" standard was all about.
Basically the clock and data are combined into a single serial stream.
This makes it a lot more tolerant to things like tape  stretching and the effects of "wow and flutter".

I'll have to dig out my old note from "back in the day".
This is the second time where I've talked about biphase encoding/decoding.
For low bandwith comms or data storage it's a really easy, reliable technique.


@Osgeld some folks accuse me of being a pinata of useless knowledge, but I confess never have heard anything like what you describe.  120MB is trivial now, but certainly was worthy back when VHS was new.  Any idea how does it operate?  

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