Can anyone help me interface a basic stamp to a microtape assembly to store dat
Jadoo
Posts: 2
Hi Guys,
I recently came across an old answering machine the kind that uses microtapes. After taking it apart i have all the components but the drive circuitry that normally drives the record and read heads but it is very large. I was intending to use the microtape as a data storage medium. My plan is to have a small eeprom to store data temporarily and when it gets full the data is archived onto the microtape. Im not really sure how I could do this and also not sure how many different tracks the microtapes have for storing data or how much data could actually be stored. Could anyone help me out and tell me how I could design a circuit that would interface directly with the read and write heads so I could use the tape deck in this manner?
If you are aware of any similar exisiting applications could you also post a link for them if it is availible?
Any information would be appreciated.
Many thanks
Arridh
I recently came across an old answering machine the kind that uses microtapes. After taking it apart i have all the components but the drive circuitry that normally drives the record and read heads but it is very large. I was intending to use the microtape as a data storage medium. My plan is to have a small eeprom to store data temporarily and when it gets full the data is archived onto the microtape. Im not really sure how I could do this and also not sure how many different tracks the microtapes have for storing data or how much data could actually be stored. Could anyone help me out and tell me how I could design a circuit that would interface directly with the read and write heads so I could use the tape deck in this manner?
If you are aware of any similar exisiting applications could you also post a link for them if it is availible?
Any information would be appreciated.
Many thanks
Arridh
Comments
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Chris Savage
Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777
Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
Designs Page:··· http://www.lightlink.com/dream/designs
·
Modems and tape machines have different problems. Tape speed is not constant due to motor variations and tape stretching so you usually use some sort of self clocking mechanism.
If you really wanted to roll your own, you might try something simple first. Generate, say, a sync tone of 10mS. Then at least 5mS later generate a 5mS tone for a zero and a 10mS tone for a 1. This would be detectable with the Stamp just by looking for audio versus silence. You might have to stretch the times to account for noise levels and processing time. In fact, maybe start with 1S and 500mS then turn it down until it quits working.
This would require almost no extra hardware -- the Stamp can generate the tones and the playback would just have to have a transistor to clip the audio input. Hmmm... maybe this is a project of the month brewing. I have a few "big" ones that I haven't had time to do, but this would be fun. Gotta find an old tape recorder.
Regards,
Al Williams
AWC
Add Floating Point Math to your Stamp
http://www.awce.com/pak12.htm
P.S. I'm not suggesting that that scheme is how the KC standard worked. In fact, if I recall it was some form of FSK (that's been a long time ago -- can't remember). But the Stamp would find it hard to reliably decode tones (a 567 would do the trick though). I'm just saying that the above scheme would require very little hardware and would work if your S/N ratio was high enough. An RC filter could help it. Data rate will be low and slow though (forgive the rhyme).
Post Edited (Al Williams/AWC) : 9/4/2004 2:20:51 PM GMT
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Chris Savage
Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777
Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
Designs Page:··· http://www.lightlink.com/dream/designs
·
(If they loaded at all. The trick was to use a deck with adjustable pitch, and chanting 'Speccy, Speccy, computer over all others' while crossing your fingers)
Anyway. A microcassette is typically 15Minutes on one side, and unless you build a mechanism to swap tapes or turn them around, that's all you get.
(All my microcassette tapes are this size, but since they came with a 22year old computer... )
Say 300bps, no 'extra start/stop bits' or synch signal, this gives 37.5Bytes/Second or 2250Bytes/Minute.
Even if you have only a short synch pulse at the beginning, skimp on the start/stop bits and only have the most necessary error correction, you won't be able to fit more than say, 30KB on a single side of the cassette. (And that's in a single data block. If you want to record several sessions you must leave open gaps on the tape, wasting precious seconds every time. )
Using a 'normal' cassette and 120minute tapes, which will give you 60minutes on one side, though, should give 4 times that storage, and should help a lot.
And getting the speed higher will also help a lot.
I doubt that PBASIC is capable of handling more than 150 or 300bps on anything but the BS2p.
(Every time someone claims something is impossible to do with the BS2, someone quickly proves it othervise. So what are you all waiting for?)
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Chris Savage
Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777
Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
Designs Page:··· http://www.lightlink.com/dream/designs
·
This way it would not matter what speed the tape is moving at. You would simply look for the presence or non-presence of a clock on one
track, and do an AND comparison with the other track to reconstruct your data. I forget how many cm per second (...I think 2.4) the
average tape travel is, or what the typical roll off frequency is for the audio. A simple test should easily determine the max frequency response,
and from there I would back off say 10% and use that as the carrier frequency for the CLOCK and DATA. Setting a higher carrier frequency
should allow for a better storage ratio.
I'm thinking that you could use the SEROUT from the STAMP to drive the enable on a carrier frequency generator (or tape bias generator) going
directly to the tape. For the receiving end, the tape would drive a 567 tone decoder set to look for the carrier frequency with an output from the
567 connected directly to the STAMP awaiting the data with a SERIN command. Now you could send the data in the form of packets designed in
a way to give the STAMP time to do it's overhead "thinking" when receiving the packets.
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Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Firstly how do I interface the stamp and 567 to the read and write heads? Im not sure exactly how these devices work, I have a very brief understanding but can anyone give me some input for this part?
Finally I noticed that the mechanism has an optical encoder built in so that the number of rotations and the position of the spindle rotating the tape can be calculated. Could I use this instead of a clock signal, Im not too sure on tape streching that is why I ask?
If somebody does decide to write this as a project can you kindly send me a copy [noparse]:)[/noparse] ** Hint to Al ** Im not sure if I will be able to get the relevent magzines here in Australia.
Many Thanks
Arridh
b) It will be several months before I would get to this if at all
c) The Stamp Project of the Month is on the Web and free (http://www.awce.com/som.htm).
Al W.
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Chris Savage
Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777
Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
Designs Page:··· http://www.lightlink.com/dream/designs
·
Project of the year 2004, Al ??
Regads,
Klaus
Kansas City standard
The Kansas City standard (abbreviated KCS) for storage of data on an ordinary audio cassette was also known as the BYTE standard or the CUTS (Processor Technology Computer Users Tape Standard).
Developed in 1975, it uses asynchronous serial data encoded using frequency shift keying such that a '0' bit is represented as 4 cycles of a 1200 Hz sine wave, and a '1' bit as 8 cycles of 2400 Hz. This gives a data rate of 300 bits per second.
Computers using the Kansas City standard included:
* Several S-100 based systems, such as MITS Altair 8800
* PT SOL-20
* Ohio Scientific C1P/Superboard II
* Compukit UK101
* Acorn Atom
* Nascom (which also supported a 1200 bit/s variant)
* Motorola MEK D1 6800 microcomputer board
* SWTPC 6800 based computers
External links
* Sound sample
* SWTPC AC-30 cassette interface
[noparse][[/noparse]url]http://www.fact-index.com/k/ka/kansas_city_standard.html
I had one of the SWTPC interfaces connected to my home-brew 6502 based computer. It worked like a champ, albeit slow. But "slow" is relative, 300 bits per second was the going modem speed in those days!
The SWTPC link includes schematic diagrams to give you an idea of how it worked.
Russ
I know those names. Heck, I· even thought about building an S-100 bus based machine at one point. That was just before I met and appreciated an Apple II+ machine. The S-100 bus has on it the exact same screwy signals that the 8080 had. To use any other processor such as the Z-80, who's were simplified, was a major undertaking. For your problems, and the inevitable solutions, here's a hint, try to find a copy of Don Lancaster's TV Typewriter Cookbook. It contains all of what we're discussing. As a matter of fact, the majority of systems actually used his ideas with out even knowing it.
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Buck Rogers
www.gregg.levine.name