The chiffchaff is a very cute singing bird that is quite common in Hungary. I started this project because I really like the song of this bird and I wanted to create something in the "business card" form factor.
The heart of the build is the speaker which was salvaged from an old Nokia 3310 cellphone. It is driven by a single pin of the ATtiny45 through a low pass RC filter.
This microcontroller has only 4 kbytes of program space so it was a real challenge to fit the song of the bird in it. The original .wav file was first clipped, then encoded into a 1-bit bitstream with the "BTc Sound Encoder" software from Roman Black. Finally, the small pauses in the bird song were removed and it was splitted into 3 separate "chiff"-s for better storage.
The microcontroller is in deep sleep most of the time. It only wakes up when the button is pressed and it goes to sleep immediately after finishing the song.
The PCB was manufactured using a DIY UV exposure box.