Muzzer: a melody card that plays on touch

A board the size of a card, three songs in the chip, no button. Touch pad B and the next note plays; touch C and the song changes, the card beeping as many times as the song number. An ATtiny412 sleeps almost without current between touches and wakes through two Darlington transistors that sense skin contact.

Why these pins

On the ATtiny412 only PA2 and PA6 can wake the chip from the deepest sleep, because only those two lines detect edges asynchronously. The electrodes therefore sit exactly there. A third switch on PA3 would be dead during sleep and was dropped.

Flasher without a computer

The card comes with a second small project: an ESP32-C6 that carries the compiled program in its own flash, waits on the UPDI line, sets fuses, writes the ATtiny and reads it back. An LED reports success or failure. Cards can be programmed in series without a laptop on the table.

Status

Firmware in two variants (standard, Turkish march), board in KiCad, Gerber exported, bill of materials documented as its own page.