Having found an online QR code generator, I fed the URL for my blog into it, and it produced a QR code small enough to fit onto a ZX81 screen. Next step was printing it - I then drew a grid over the top, splitting it up into 17x17 ZX81 characters. It was then easy enough (although very time consuming) to map it all to ZX81 graphics symbols, printing the whole lot on screen using 17 lines of BASIC. It all took longer due to some problems with RAMpack wobble about halfway through, which was annoying, but after that I saved it after doing each line. Eventually I finished it...and was pleased to find it worked! Well, sorta.
That's it screen-grabbed running on the EightyOne emulator on my PC. It works instantly with no errors, and I got it right on my first attempt. However, running it on my real ZX81 is more problematic, probably because of the crappy, tiny telly I use as a "monitor". However, a printout from my Alphacom 32 printer worked just fine, despite the dubious print quality. A reasonable quality TV display should make it simple enough to read one of these without too much trouble.
There's no real point to this, of course, but it kept me busy for a while, and it was satisfying to get it right first time, and do something the thirty-year-old ZX81 was NEVER designed for. I suspect the coding process for QR codes is simple enough to make a ZX81-based coding program possible. I might give it a go...
Lee
