How to save and output Audio signal ?

[emax0198]

How a microcontroller can be used to save an audio voice conversation and then output that to a speaker? It is easy to do this using additional components but how to do this only using a single microcontroller?

 

[IanP]

To do this you will need a microcontroller with a A/D and D/A converters and some memory. If you log data from analog port at a rate of, say 8000/s (twice the highest frequency as per Nyquist cratirion ≈ quality of a telephone) and store all logged data in a memory.
The playback through D/A converter has to be done at the same rate as recording.
Regards,
IanP

 

[throwaway18]

There are few models of microcontrollers that have a built in DAC but you may be able to use a PWM output instead. With a quick search I can't find any uC with a DAC and enough RAM to store more than a fraction of a second of audio.

Storage will be a big problem. Flash memory in microcontrollers is usually too slow for such use so you need RAM. 16Kbyte RAM is big for a microcontroller.
If you store raw audio 8bit/sample you need 8K for each second of audio.
1MB with a microcontroller usually requres an external RAM chip.

It might be possible to implement a speech compression such as GSM codec (9600bit/sec) or speex algorithm(down to 270bytes/sec) in a fast microcontroller.
Probably not cost effective.