Multiple frequency audio tone generation

[joeyh]

I am trying to see if there is a way I can generate a multi frequency audio signal without additional hardware.  I am talking about something similar to DTMF.  The audio wave will contain say 3 fixed frequency tones.

i wonder if I can use PWM library for this purpose.  But, it looks like I can only generate 1 frequency per output pin.  How about using the DSP capability of the NRF52 chip?

Any idea will be greatly appreciated.

Thanks,

Joseph

[Elias]

Would square waves be acceptable fixed frequency signals? If so, all you have to do is make a few timer interrupts, each toggling the same pin at twice the frequency of the desired output frequency.

[NewtoM]

Hi, you can have a look at this PWM audio thread.