In contrast, the original ZX Printer (and Alphacom 32 / Timex 2040 printer) could just work with the LLIST, LPRINT and COPY commands to produce a program listing, plain text or a screen dump respectively.
The Spectrum and ZX81 screens are relatively simple, so what we need is a simple interface which would plug into the expansion port on the ZX81 and Spectrum and when COPY was entered, it would grab the screen and send the bit data over a centronics cable to the Retro-Printer. The bit data would need to be pre-fixed by something to indicate that it was a ZX81 / ZX Spectrum screen dump, but the conversion to printed format could then be added as a new filter on the Retro-Printer module.
The other options would be a button to press to take a screen dump and presumably a jumper to switch between the ZX81 and ZX Spectrum.
We just need someone to get onboard with designing the interface
