Term0

[ by Matteo Vitturi - 2022 - for Sinclair ZX Spectrum Next ]

This tool starts a bi-directional communication stream with the Raspberry Pi-Zero accelerator.

[BREAK] quits to Basic with L BREAK into program.

[TRUE VIDEO] produces EOT or ^D  (0x04) that normally produces a 'normal exit' from whatever you where in.

[DELETE] produces BS or ^H (0x08) and it is the normal back-space key.

[>=] produces ETX or ^C (0x03) that helps to emulate CTRL-C key-press.

~ | \ [ ] { }  are produced via SYMBOL-SHIFT 

The rationale is as follows. The main loop continuosly polls the keyboard and polls PI0 UART: Any key pressed is immediately transmitted, any byte read from PI0 is immediately sent to screen, which is notoriously slow.
[ENTER] key has a peculiar behavior and, once 0x0D is transmitted to PI0, up to 8000 bytes are "fast read" from UART and - only then - slowly sent to screen. This allows collecting long output from PI0, but only after you hit [ENTER].