"First, catch your rabbit." - Old recipe for rabbit stew. This lists a real serial modem as a prerequisite, and those are kinda getting to be collectors' items

"First, catch your rabbit." - Old recipe for rabbit stew. This lists a real serial modem as a prerequisite, and those are kinda getting to be collectors' items. Is it feasible to build a modem out of a Raspberry Pi Zero or an Arduino? You'd need to hook the phone line to the GPIO pins, do the ADC and DAC stuff in software, implement the V.22 protocol in software, and also implement the Hayes Smartmodem stuff in software, meaning this is one of the few times a Hacker News reader would have occasion to implement the Hayes Code. Is there any show-stopping problem I'm not seeing? Massive electrical incompatibility?