17 replies to this topic

[radar]

I remember reading once that it's possible to store any type of data onto a standard blank audio cassette tape. I did a Google search but couldn't find any relevant info. How is this done?

[biosphear]

I remember reading once that it's possible to store any type of data onto a standard blank audio cassette tape. I did a Google search but couldn't find any relevant info. How is this done?

I have heard that also but do not think you can. I do believe it is a myth. My basic understanding of data formats, it would be like writing a program to a LP. You would have to convert it to an analog format.
It might be possible but I would see no use. It would be a cool item to check out.

[Lord Wud]

http://en.wikipedia....ter_peripherals

My first computer was a hand me down Atari that only had BASIC.
Books of programs were sold that you had to type in yourself.
You could then save them to a cassette drive.
If you played the cassette in a normal player it sounded similar to fax/modem tones
I believe Amiga used similar technology.

[mungewell]

You don't say how much data you want to store, or how often. Although I don't know of an immediate project to suggest, the solution will probably be to use a audio band modulator/demodulator such as AFSK. These are used in HAM radio so there are some applications out there, such as multimon (http://www.baycom.or...x/multimon.html) which can decode stuff - I'm sure that there's a software encoder out there too.

The other problems you'll have to overcome are bit corruption, wow-flutter and tape stretch. If you packetise your data and include forward error correction you might be able to get around these. If designing a system from scratch it might be worth while 're-purposing' and existing scheme. What ever you chose would have to be 1 way (ie. no feedback to issue resends!)

Depending on your data contents (ie. numeric, ASCII or 8bit binary), you might like to take a look at the Datamatrix (2D barcode) system. Normally the Data matrix uses a maximum array of 144x144 pixels to represent up to 3116 (numbers) or 1556 (bytes), but these can be stacked into a group of up to 16 barcodes giving a storage size of around 24K. Rather than rendering to a bitmap you could take the byte code and pass it to an AFSK (or the like) modulator.

There was also a project called DVbackup (http://dvbackup.sourceforge.net/) which did some research into error detection/correction.

Cheers,
Mungewell.

Edited by mungewell, 13 May 2008 - 07:23 PM.

[systems_glitch]

I have heard that also but do not think you can. I do believe it is a myth. My basic understanding of data formats, it would be like writing a program to a LP. You would have to convert it to an analog format.
It might be possible but I would see no use. It would be a cool item to check out.

You laugh, but data LPs were actually created as cheap ways to distribute data. They weren't very popular or common, but I've heard of them, and seen a few supposed pictures. Apparently a few artists/record labels in the 80s decided it would be cool to put data on the B-side of a LP, and give the buyer some computer games with the music. Here's a quick article on it:

http://www.kempa.com...ves/000053.html

The original IBM PC, the 5150, included what looked like a second DIN keyboard port on the backplane...in reality, it was a tape port, for which you needed a special cable. The cable terminated in three 1/8 inch jacks -- play, record, and "remote"..."remote" was a function on some old tape machines that allowed a remote pause button. You had to rewind the tape yourself. Using the built-in ROM BASIC included with every 5150, you could store your programs to tape, rather than entering them by hand every time (a bare-bones PC came with no drives at all, just the tape access). You could even write out files from the BASIC interpreter to the tape. I played one, once, to find out what sort of sounds it would make, and it did indeed sound like a modem.

I used an 8-track deck with my IBM PC, because the 8-track unit on my hand-me-down stereo had the pause function, which is *extremely* handy. Later, I found a no-name portable tape player (Walkman-esque) that had a remote jack, and switched over to this. IIRC, a standard 60-minute cassette could hold around 160 KB.

[BSDfan]

Audio/VHS cassettes are analog mediums, storing "data" would require a converting digital to analog and then back again..

In the past, I believe 80's "home computers" used it as a quick cheap solution... but it's nowhere near as reliable as a cheap digital solution. (You can buy an ATAPI/IDE tape drive that can store ~40GB for less then $30 CAD.).

Anyway, digital data on an analog audio tape would probably sound like a Fax/Dial-up modem..

Hope that helps... if you do design something, make it extra-redundant, audio distortions like static will corrupt data.

Edited by BSDfan, 13 May 2008 - 03:21 PM.

[vvuiverine]

My Commodore 64 had a tape drive to store data. This is not very practical though for it is very very slow. I remember a simple program to print input vertically or horizontally across the screen would take probably about one minute to record or load from the tape drive. When upgrading to a 5.25 floppy drive it seemed lightning quick.

[BSDfan]

I have to admit though, this does sound like a neat hobby.. if someone would be willing to document the design of such a device in detail. (Pictures) that would be swell..

Thinking about the layout of the tape, I would put calibration areas at the beginning and end of the tape, because audio tape doesn't have tension and the "start/stop" sequence isn't exactly gentle or precise. (Pinpointing the begin/end of data would be a hard process otherwise..)

The computer interface could either be via the sound cards line-in/out ports, or perhaps a serial cable.. either way, it'll be "slow".. very slow.

This is exciting me, anyone else interested?

Edited by BSDfan, 13 May 2008 - 03:34 PM.

[sshblack]

Sometimes I honestly wonder how you guys know all this stuff?!!!

My Commodore 64 had a tape drive to store data. This is not very practical though for it is very very slow.

Ah memories! I agree that there are simpler and better ways than starting a cassette tape up (which if I remember weighed half a metric tonne) then having to type in LOAD everytime you wanted to access your data.

[PurpleJesus]

My Commodore 64 had a tape drive to store data. This is not very practical though for it is very very slow. I remember a simple program to print input vertically or horizontally across the screen would take probably about one minute to record or load from the tape drive. When upgrading to a 5.25 floppy drive it seemed lightning quick.

There was 'turbotape' too that sped that up quite a bit...

wow.. found link to that... http://www.atarimaga...1_TurboTape.php

man.. that brings back memories.. I can still see the border rastering...

[mungewell]

I can still see the border rastering...

Yeah, I used that as well, I don't think that the tapes were as resistant to corruption though.

I love the quote from the website 'Even after you've used TurboTape for weeks, you'll still find it hard to believe that your cassettes can save and load this fast.'.

LOL,
Mungewell.

[Lurk Moar!!!!]

I remember that as well. Back in the late 80's my brother had a spectrum+2 which was a normal ZX Spectrum except it had 128k and a bultin tape drive. We got "Teenage mutant hero turtles" for it for xmas, every time you restarted a level the screen would go blank and print "Please rewind the tape to position -27 and press play" then we had to wait 15 minites. God I was glad we we got a megadrive.


This would be an interesting Project to code a program to save data to a wave file and stream it back.

[PurpleJesus]

I remember that as well. Back in the late 80's my brother had a spectrum+2 which was a normal ZX Spectrum except it had 128k and a bultin tape drive. We got "Teenage mutant hero turtles" for it for xmas, every time you restarted a level the screen would go blank and print "Please rewind the tape to position -27 and press play" then we had to wait 15 minites. God I was glad we we got a megadrive.


This would be an interesting Project to code a program to save data to a wave file and stream it back.

You have a very doable idea there. Hook up a tape recorder's mic to the line out, and it's play back to the mic input of the computer.. maybe modify some spectrum analyzer to watch for tones and make sense of it.

Edited by PurpleJesus, 15 May 2008 - 04:42 PM.

[biosphear]

You laugh, but data LPs were actually created as cheap ways to distribute data. They weren't very popular or common, but I've heard of them, and seen a few supposed pictures. Apparently a few artists/record labels in the 80s decided it would be cool to put data on the B-side of a LP, and give the buyer some computer games with the music. Here's a quick article on it:

http://www.kempa.com...ves/000053.html

That is cool. I never knew that.

[systems_glitch]

In repairing the KIM-1 I recently acquired, I stumbled across the theory of the tape storage system in the manual. The KIM-1 works by plugging two connectors to the Mic and Headphone ports of a tape player/recorder, and using them to store data. The KIM-1's tape routines include some error checking, and can be used to extract a set of data from any position in the tape, even if you don't know the exact position, as long as you know the address of the data. Here's the section on theory:

http://users.telenet...2/usrman.html#E

Elsewhere in the manual, you can find not only the schematic for the phase-locked-loop system of reading/recording data to audio cassetes, but also the Assembly source code for the KIM-1's tape routines. The whole user manual is here:

http://users.telenet...502/usrman.html

I see no reason it can't be adapted to modern application!

[craygee]

w00t!! I had a ton of games on my atari cassette backup. A cassette is only magnetic storage. Of course you could put information on one it still works on the same basic principle of magnetic storage today. But as Mungewell mentioned, it was pretty prone to issues.

[C'thulhu]

One hobbyist method was called the Kansas City Standard.

http://en.wikipedia....s_City_standard

[barcode_]

Store as barcodes in database?