I am putting here my ALSA program in order to have a backup.

This also serves as an Arduino library for the SAMD21 board with the PCM5102A DAC

PCM5102A   SAMD21
Vcc        5V
GND        GND
FLT
DMP
SCL        GND
BCK        D1
DIN        D9
LCK        D0
FMT        GND
XMT        3.3 V

MIDI IN  D11

./modular <program> to exec the program
./modular -c <program> to list the SAMD21 synth.ino program
./modular -p <program> to list the synth.cc program