Assume a computer (Raspberry Pi, Mac, etc.) is used to connect to a radio (HF transceiver, etc.) via audio cable(s), USB port, or GPIO, etc.
What contemporary computer DSP/digital modes, of those popular and useful for low signal-to-noise ratio channels, can be used to communicate via just an ASCII text terminal for the computer? (e.g. no OpenGL GUI, Windows, VNC, RDP, CocoaTouch, no PPP/SLIP, etc., required)
For instance, there exists a utility for the Raspberry Pi that allows transmitting WSPR, controlled from either a serial port connection or an ssh terminal command-line. Any others? Any receivers? Any FT or JT or similar modes suitable for a full text-terminal-only QSO?
Added for completeness:
Do any of the recent modern software digital modes have existing specifications sufficient for implementation of the mode (e.g. writing DSP code rather than acquiring a "product"), and as part of the documentation, indicate how a QSO can be completely accomplished using just a terminal console (e.g. serial port connected dumb terminal)?