This project uses an Sparkfun ProMicro development board (Atmel 32u4 microprocessor) and a rotary encoder to create an external volume control for a PC. The objective is to make it easy to control the volume and mute the microphone during video calls.
The USB HID specification does not provide the ability to mute/unmute the microphone, so this functionality relies on the installation of a utility program on the PC such as MicMute to listen for a key combination and mute/unmute the microphone, or key combinations supported by specific applications. See the toggleMuteMicrophone() method for the current key combination.
The circuit schematic is shown below.
Many rotary encoders (SW1) are available, the key is to get one which has a built in switch which is activated when the knob is pressed, this is used for muting the microphone. Details of the one I used are in the docs directory.
The momentary switch (SW2) is used to turn off the HID so that the device can be reprogrammed easily. The LED comes on when SW2 is pressed.
The finished device.
The code in repository has the configuration files to allow it to be imported into the PlatformIO development environment, alternatively it may be edited in the Arduino IDE.