Noisy Zimodem
Noisy Zimodem is an ESP32 with Zimodem firmware by Bo Zimmerman https://github.com/bozimmerman/Zimodem (thanks to Bo for his fantastic work) to which I added a TTL-RS232 interface converter, a PCM5102 DAC and a mini LM386 to play sounds.
handshaking and dial tone sound is inside source code and the result, who can you see in this video, is very similar an old fashioned modem.
License
This work is licensed under a Creative Commons Attribution 4.0 International License. See https://creativecommons.org/licenses/by/4.0/.