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[on:]

For a project I am working on, I need to store serial data inside an audio file and read it back with the Arduino. I went the easy route and just ordered some single-chip 300 baud modem ICs. But those chips are actually obsolete and hard to find. So, I was thinking of throwing together a little project that anyone could build using LM565 ICs, some comparators and a few simple components. I am curious whether anyone would be interested in that?

I am aware that there is already this: http://trac.switch-science.com/wiki/ARMS22-SOFTMODEM-HOWTO which uses software to do the work.

Since I am already planning to use a modem IC for my purposes and the above library exists, I don't know if it is worth the effort to put something together. With the library above, it will take up code space in your Arduino, so perhaps an external method would be useful?

[Reply #1 on:]

For a project I am working on, I need to store serial data inside an audio file and read it back with the Arduino.

I haven't figured where a modem comes into this - or an Arduino come to that.

Where is the data file?

What is the source of the serial data that needs to be written to the file?

What is the destination of the data after it has been read back out of the file?

[Reply #2 on:]

Hi Peter,

This is part of my animatronic (late) valentine's day present for my girlfriend. I will be playing MP3 files which will have the audio stored on one channel and serial data stored on there other. The serial data will be used to control the character. Basically syncing it up to the audio.

The modem is just used to convert the serial data into audio and vice-versa. A modem is really kind of overkill for this, but it is simpler to implement.

Other uses for something like this would be to store data on whatever media you want (or even over a telephone.) The softmodem (not mine) was designed for allowing easy transfer of info from an iphone or android phone, for example.

[Reply #3 on:]

That use of audio streams to carry a data side band sounds very neat, although encoding the data as audio using a modem seems rather crude. I suppose it saves you from having to encode/decode the file format directly.

[Reply #4 on:]

True. It would be especially crude if you weren't using a modem IC. Since you aren't using the transmit portion of the IC, anyway, might as well make use of it to encode the audio as well.

However, in discussing the discrete version using PLL ICs for example, you would only need to built the receiver portion. So, it would be better to use a program on the computer to encode an audio file.

[Reply #5 on:]

Does anybody know where you can get the Android app for the soft modem terminal? None of the links in the referenced page work (for the Android side of things, at least - I was able to find an iOS version)...

[Reply #6 on:]

Hmm... I could have sworn I stumbled on it while doing google searches. Haven't found it again, though.