PolyPhonic Sound & Mono Sound

[kjts]

Hi,

Is that possible change the nokia mono sound to polyphonic sound?
let say changing nokia 3310 mono sound to polyphonic sound?
i heard that changing the buzzer to polyphonis buzzer will get the polyphonic sound...is that true? someone get any idea on it??

[wumpus]

No. This is not possible. I have tried it in several ways and failed..

The problem is that the polyphonic phones have a full sound system (sampler D/A converter) hooked to a MIDI interface. (Like a PC sound card) The buzzer is a simple clock divider that divides the 13mhz clock into ONE audible frequency. (Like the PC internal beep speaker)

You could try emulation though in a few ways:

1)
Possibly you could emulate something using PWM, a long time ago I had a program that could play wav and mp3 files through the PC internal speaker, but the quality would suck.
Another problem is that this "solution" would need 100% of the processor to switch the signal fast enough. Too bad the phone MCU is quite busy during a call, the DSP is hooked with decoding GSM signals and the ARM with processing packets and state.

2)
Of course, a phone does have a PCM sound system (Cobba 8khz) for voice, but the maximum volume of the voice speaker is not enough for using it as buzzer.
Possibly, this could be augmented in some way, but I wouldn't hold my breath for a software-only solution.