Code to drive a homegrown teensy based footswitch. The footswitch is operated by grounding PIN11 on the teensy (I currently use a reed switch and a magnet), which sends a serial command to a python daemon which in turn sets the macOS system input volume to 0. When the circuit opens, the input volume is set to 100.

The config file sets the metrics reporting server, the serial port to use and the prefix for the metrics reporting.

[default]
serialport = /dev/cu.usbmodemNNNNNN
switchmetric = 1min.graphite.metric.prefix
carbon_server = localhost
carbon_port   = 2003

The mute-daemon python utility and the mute-atr.scpt must be executable and in /usr/local/bin, and the config file should be in /usr/local/etc/mute-daemon.cfg.

The teensy code should be loaded onto the board, and the mic is muted by grounding PIN 11. If an LED is attached to PIN 9, it will illuminate when the mic is "hot", and if an LED is attached to PIN 10, it will illuminate when the mic is "cold". The LED will not change until the Mac has muted the system-level input and the mute-daemon has responded to the teensy.

Manually changing the mute state of the Mac will not be reflected by the LED.