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By doobie
#95666
Anyone here ever create a DIY walkie-talkie? I'm looking for a digital solution that I could use to both transmit data and voice. I'd like to be able to have multiple users talking and transmitting data. What I'm having trouble with is determine how to convert voice into digital data (mic with analog data input?), then from digital data back to voice (assume this is probably via PWM).

Thanks for any help!
By markaren1
#95667
Excellent project !

Do a search for low bit rate, low complexity audio coder. It's probably going to use a DSP with analogue interface via ADC and DAC.

GSM uses a 13kb/s codec which is open. I have seen several implementations on the web.

On the radio side, you should be able to frame the data to 115k baud and use am Xbee pro module, or similar.

There are many higher complexity, lower bit rate coders available, but reducing them from a 'lifetimes work' down to 'a hobby project' is of course the trick.

Also do a search on Spread Spectrum voice link and see what you uncover

Regards,

Mark
By theatrus
#95674
An audio codec is going to save you a lot of bandwidth, a good suggestion. You can of course always implement a raw PCM stream with FSK or even ASK modulation, but the bandwidth requirements are large.