So to implement everything with your Raspberry Pi, you can clone my repository:

cd ~
git clone https://github.com/mrwunderbar666/rpi-vumonitor-python.git

Make sure you have all the dependencies installed:

sudo apt-get install python-rpi.gpio
sudo pip install psutil
sudo pip install wiringpi

And if you want to use a DAC, check the respective repositories.

After the dependencies are running you can run one script with your preferred method:

cd rpi-vumonitor-python
sudo python pwm_vumonitor.py &

Start at boot

If you want to launch the script automatically, you can do that with a shell script and add it to your crontab:

cd ~
nano startup.sh

Add the following code to the startup.sh file:

sudo python \home\USER\rpi-vumonitor-python\pwm_vumonitor.py &

and then add to your crontab via sudo crontab -e:

@reboot bash \home\USER\startup.sh