Author Topic: Calculator Audio Demodulator  (Read 5280 times)

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Offline systwo

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Calculator Audio Demodulator
« on: January 15, 2012, 05:00:59 pm »
Hello to the community of Omnimaga!

I have been thinking of alternate methods to transfer data from the computer to the TI83+. You may be asking "Why not use the USB cable or serial cable?" To answer those questions, I have decided to take on a challenge (and I also don't want to shop for one. They are so expensive!). Seeing the I/O cable is very similar to an audio cable, I thought maybe that it could be spliced to a 3.5mm jack. All it would require is a small program on the calc to receive the data and save it.

So, to those who are more enlightened to the ways of audio and in the higher ranks of assembly programming: Are there any pitfalls one may have to look out for?



Thanks!

Offline Xeda112358

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Re: Calculator Audio Demodulator
« Reply #1 on: January 15, 2012, 05:03:17 pm »
I am curious, too, and my initial reaction is to say you probably won't have to do any special programming if you want to use it as a serial cable.

Offline systwo

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Re: Calculator Audio Demodulator
« Reply #2 on: January 15, 2012, 05:13:49 pm »
I'm just worried that the PC will not allow me to access the audio port as a two way device, as it is meant for one way signals. So there won't be any checking and acknowledgement that the transfer got thru. Also, I wasn't thinking of it as much of a "serial cable". I though of it as a system where one would encode the program into audio and then play it with a media player to feed it through the audio to the calc's I/O. 

Offline Xeda112358

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Re: Calculator Audio Demodulator
« Reply #3 on: January 15, 2012, 06:58:51 pm »
Oh, wow, I see what you mean, now O.O Yeah, there won't be a need for calculator stuff, but on the computer end, yes. That would be an excellent endeavor!

Offline alberthrocks

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Re: Calculator Audio Demodulator
« Reply #4 on: January 15, 2012, 07:05:06 pm »
If it doesn't work out, you can always make it so that it plays sounds that can be read by the calc and be parsed into data.

You know what would be awesome? Sounds played via speaker that we can't hear, but a microphone (connected to an Arduino?) that can interpret and parse it. The result? Some serious wireless calculator linking! :D
« Last Edit: January 15, 2012, 07:05:50 pm by alberthrocks »
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Re: Calculator Audio Demodulator
« Reply #5 on: January 15, 2012, 07:07:28 pm »
Wow, that would be amazing!  Great freaking ideas! And you might be able to make the mic port on a computer read data sent from the calcs, too.

Wow, wireless might be possible for the calc in a new way... We would need a specially made device hooked up to the calc, but using sound is a neat idea!

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Re: Calculator Audio Demodulator
« Reply #6 on: January 15, 2012, 07:30:45 pm »
On TI-Planet someone actually wondered if it would be possible to transfer stuff from the calc to PC or vice-versa via the audio out jack of the computer, but ran into the two-way transfer issue. Basically you would need to use the mic port for one kind of transfer and the audio out (headphones) port for the opposite. However I heard that using the mic port could be busted by doing that because of voltage issues. I wonder if the audio-in port could be another alternative... the issue is that not every computer has an audio-in jack...

http://tiplanet.org/forum/viewtopic.php?f=41&t=8652 (French)
« Last Edit: January 15, 2012, 07:39:01 pm by DJ_O »

Offline alberthrocks

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Re: Calculator Audio Demodulator
« Reply #7 on: January 15, 2012, 08:01:32 pm »
Yeah, it's likely that inaudible audio (too high/too low) with a microphone and speaker on both ends may be the solution.
It's cheaper than actual wireless (at least $20 for a crappy board, $50+ for a good one).

You could also use the upcoming RaspberryPi - ARM board that you could throw Linux on and write the encoding software there! :)

I'm curious though - how fast would the sound pulses have to be, and can regular audio transfer handle that?
Would a difference in pitch be involved as well?
« Last Edit: January 15, 2012, 08:03:52 pm by alberthrocks »
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C2I: 0% done (planning, checking the demand for it, and dreaming :P)

Offline systwo

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Re: Calculator Audio Demodulator
« Reply #8 on: January 15, 2012, 08:13:02 pm »
I read about homemade serial cables a while ago and it may be the solution. Serial cables had the same problem so those who made it would use 4 of the pins, 2 for in and 2 for out. To manage the flow of electricity, they would have diodes that control what direction the data flows.

My design would look something like this

PC Audio Out tip -> diode -> tip splitter -> calc tip
PC Aduio Out ring -> diode -> ring splitter -> calc ring


PC Audio In tip <- resistor<- diode <- tip splitter <- calc tip
PC Audio In ring <-resistor <- diode <- ring splitter <- calc ring

The resistor would be to take the voltage back down to prevent blowing out the mic in. And according to posted article, out would not need it.


Audio may be able to handle the speed, depending on sample rate I think. I'll need to do some more research to see if they match.

Edit:
Remember that sound is basically the fluctuation between two amplitudes (up and down) and that it can be held up for a lower sounding note. The signal that the PC would send would be a square wave that has goes up but does not go below the 0 line. So pitch does play a role
« Last Edit: January 15, 2012, 08:15:18 pm by systwo »

Offline TIfanx1999

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Re: Calculator Audio Demodulator
« Reply #9 on: January 15, 2012, 09:02:14 pm »
It is a really cool idea, but off the top of my head I don't think any of the stereo inputs on a computer are two way for data. IE mic input is for input and speakers are for output. I could be wrong as I don't really know much about the subject, but it is a really neat idea! :thumbsup:
« Last Edit: January 15, 2012, 09:02:48 pm by Art_of_camelot »