Audio-in? (Datassette)

RedNifre

Hello!

I was just thinking about the C64 and how cool it was that you could store digital data on standard audio cassettes. I wonder if it would be possible to do that with the hydra using a standard cassette-recorder.
The Hydra has a sound output, so you could at least create a WOM (Write Only Memory). But how to read the data back in? Could you somehow read from an "output"? Like, writing on audio-out, reading on video-out? Or do I have to use the blank experimenter card for this? How hard would it be?

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Unterwelt (My first game for the HYDRA):
http://forums.parallax.com/showthread.php?p=696204

Hydra in a LEGO NES:
http://forums.parallax.com/showthread.php?p=654788

PJAllen

The idea is called "FSK", Frequency Shift Keying.· One frequency is a "0" and another frequency is a "1", there can be a carrier frequency which is neither a "0" or a "1".

RedNifre

Thanks for the reply!

Looks like I did not phrase my question clearly... :-/
The process of mapping binary data to sound is clear to me. I'm really asking about the very basic thing of getting the sound from a cassette into my Hydra.

I just checked the book and it looks that there is no easy way of getting the sound into the Hydra. So I guess I'll have to use the experimenter card for that. Is that feasible? (I have no experience in soldering)

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Unterwelt (My first game for the HYDRA):
http://forums.parallax.com/showthread.php?p=696204

Hydra in a LEGO NES:
http://forums.parallax.com/showthread.php?p=654788

Spork Frog

I'd take a look at the Demoboard if you haven't already, which has an on board microphone. It's possible, I just personally don't know any of the details.

Mike Green

You're correct. There's no audio input or analog to digital converter circuitry. The circuitry used on the Propeller Demo Board where the Propeller does the analog to digital conversion requires that the few components be mounted physically close to the Propeller chip which is not practical on the Hydra board. You'll need some kind of external signal conditioning. You could use an external analog to digital converter chip like the ADC0831 or even something as simple as a zero-crossing detector since you only need to find the dominant frequency of the input. I don't have any handy links, but maybe someone else can chime in with one.

PJAllen

http://forums.parallax.com/showthread.php?p=695936

Oldbitcollector (Jeff)

@PJ Allen:
It's a shame that he didn't leave source code before he went onto other things...
I've been working on a reverse engineering of that project for .TAP files, but
have hit a few walls I haven't gotten over yet...

OBC

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New to the Propeller?

Getting started with the Protoboard? - Propeller Cookbook 1.4
Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
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Need a part? Got spare electronics? - The Electronics Exchange

whicker

RedNifre:

Have a look at the schematics for a VIC-20, C64, or TI-99/4a. The cassette circuit is extremely simple, with a few biased transistors and filter capacitors. The signal itself is technically digital.