Getting to grips with the parallel interface

Interfaces used to be so much more diverse and interesting. Now everything seems to connect via USB.

And, you know, that’s probably a good thing. Gone are the days when you’d buy a peripheral only to find that it used an interface your computer didn’t have (Firewire, for example). Or your computer did have the interface but using an entirely different kind of connector (looking at you, SCSI).

That said, I have an unreasonable attachment to my Epson MX-80F/T III printer. It’s a classic 80-column dot matrix printer that I bought in 1983 for the equivalent of about three weeks’ wages (maybe more). You’ll be reading more (much more) about this printer and the various ways I have attempted to continue using it in Machina Speculatrix in the months to come.

For now, though, let’s focus on its interface. Back in 2017, when I dragged the printer out from the understairs cupboard, my intention was to design and build my own converter so that I could talk to the printer directly from the UART (or serial port) of a Raspberry Pi or microcontroller. But that meant understanding the printer’s Centronics parallel interface. How hard could that be?