demo.mp4
This is an interesting module that can decode DTMF tones and transmit them over a 4-bit bus. The way it operates is whenever it detects a tone, the pin named STQ goes high. Then, you can read each pin Q1-Q4 to obtain a 4-bit value representing which digit the tone is equivalent to.
It's probably possible to connect a microphone to the IN input and decode DTMF tones over the air. However, I currently don't have a microphone module, so I used a tone generator app on my phone to produce the tones.
cargo run -p dtmf- Component details: https://components101.com/modules/mt8870-dtmf-decoder-module