[Jacques] thought his doorbell was too loud, so of course the first thing that came to mind was replacing the electronics and playing a WAV file of his choosing every time someone came knocking. What he ended up with is a very neat circuit: he used a six-pin microcontroller with 64 bytes of RAM to play an audio file. (French, Google translation)
The microcontroller in question is a PIC10F322. one of the tiniest PICs around with enough Flash for 512 instructions, 64 bytes of RAM, and a whole bunch of other features that shouldn’t fit into a package as small as a mote of dust. Without the space to store audio data on the microcontroller, [Jacques] turned to a 64 kilobyte I2C EEPROM. The PIC communicates with the EEPROM with just two pins, allowing it to read the audio data and spit it out again via PWM to an amplifier. The code required for this feat is only 253 instructions and uses just a few bytes of RAM; an impressive display of what a very small microcontroller can do.