Old-school rotary phone dials into online meetings

"30 percent of the knowledge required, and 100 percent of the underestimation of how hard the other 70 percent would be,"

"The rotary dial is similarly a second switch, one that opens and closes very quickly, a number of times equal to the number you just dialed,"

"The software on the RP2040 just counts these opens and closes, waits a few milliseconds to see if there are any more of them, and, if not, simulates a keyboard typing the number it counted."

An old Siemens rotary phone was converted to interface with modern video conferencing. The handset was wired to an inexpensive USB sound card to handle audio input and output. The sound card connected through USB hubs to a Raspberry Pi RP2040 microcontroller that simulates keyboard shortcuts to join or end calls. The RP2040 monitors a GPIO pin pulled when the receiver is hung up and reads the rotary dial pulses to type meeting ID digits. The microcontroller counts open/close pulses, debounces briefly, and simulates keystrokes for the digit. The device produces noticeably vintage handset audio compared with modern headsets.

Read at Theregister