Author: Axel Berndt
This repository holds some useful code for the Raspberry Pi. It is tested and runs under Raspbian Jessie.
The file ShutdownRebootButton.py is a Python script that drives a shutdown and reboot button on GPIO pin 13 (GND on pin 14 or any other ground pin). Put it to a location on your Pi, say /home/pi/myTools/, and add the following line to /etc/rc.local before exit 0.
python /home/pi/myTools/ShutdownRebootButton.py&
Than reboot and the script will run in background. Pressing the button for more than 2 seconds up to 5 seconds triggers a reboot. Pressing the button for more than 5 seconds triggers a shutdown. Pressing the button for less than 2 seconds does nothing.
The file RotaryEncoder.py is a Python script that reads a rotary encoder connected to GPIO pin 16 and 18, GND on pin 14 or any other ground pin. Some encoders have inverse direction; in this case swap the values of the global variables GPIOpinA and GPIOpinB accordingly. This solution is quite robust and works without debouncing. Hence, no artificial delays are introduced. However, very quick rotation may lead to missing state changes and, hence, a few wrong results can occur. Furthermore, most users will not need the locking and can safely remove everything on that (wherever variable lock occurs). To run the script, put it to a location on your Pi, say /home/pi/myTools/, and write the following line in the terminal.
python /home/pi/myTools/RotaryEncoder.py&
This will execute the script in background and produce terminal output whenever the encoder rotates. To stop the script write
ps -elf | grep python
at the terminal and find the process id (PID) of the script. Then execute the following line and insert the right PID.
kill -9 PID
The Python script VolumeRotaryControl.py reads a rotary encoder connected to GPIO pin 16 and 18, GND on pin 14 or any other ground pin, and controls the ALSA Master volume. It is based on the script RotaryEncoder.py, so have a look at the above section and the respective code to find further details. Put the script file to a location on your Pi, say /home/pi/myTools/, and add the following line to /etc/rc.local before exit 0.
python /home/pi/myTools/VolumeRotaryControl.py&
This script requires the python-alsaaudio package to be installed! If it is not, execute the following terminal command.
sudo apt-get install python-alsaaudio
After the next reboot the script will run in background and allow you to control the Master volume via a rotary encoder. To access a different ALSA channel or have access to the separate output lines (e.g., left and right from a stereo channel) have a closer look into the code and find the corresponding comments and code lines in method rotaryInterruptA(). Further documentation of the alsaaudio package can be found here.
The Python script ShutdownRebootVolumeControl.py is a combination of ShutdownRebootButton.py and VolumeRotaryControl.py. It is handy for those who use a rotary switch. To use it place it on your Pi, e.g. in /home/pi/myTools/, and add the line
python /home/pi/myTools/ShutdownRebootVolumeControl.py&
to /etc/rc.local before exit 0.