The system looks like it could support CP/M and i think i’d seen mention of it somewhere on the web, but i certainly could not find disk images.
I google “Lexitron” regularly just to see if any new material has been added. In June 2021, i was surprised to find that some disk images had been uploaded to archive.org. That person really did me a huge favour.
https://archive.org/download/lexitron-vt-disks
Amongst the images were some CP/M disks. Just one problem – they were in Kyroflux format. By 2021 Greaseweazle was certainly available and it did have Kyroflux support. I’m not sure why i didn’t head straight down that path – it’s lost in the annals of time.
In any case, it turned out that an Adelaide Retro Computer Group member, Mick S, had a Kyroflux, and he was kind enough to write all the images to floppy disk for me.
It was awesome to find that some of the disks worked:
- CP/M system disk with assembler and debugger
- Supercalc
- DBase II
Unfortunately, I had no joy with mbasic or wordstar. The wordstar disk seemed ok, but the binary just terminated with no message.
At this point, i discovered that the fidelity of my keyboard fix was not great! If I typed fast enough it worked, but if I stopped then the last key autorepeated forever. I wasn’t particularly surprised.
This meant re-opening the source code. I thought perhaps I needed to send a second keycode to indicate that the key had been lifted. I tried lots of experiments (guesses) but I found that a null (character 0) delivered straight away seemed to resolve the issue.
Then the second issue appeared. The control key. I guessed it was the special shift, but once special shift was hit it stayed down forever and a null didn’t clear it. I tried a lot of different things – a lot – but eventually I found that if, when the key was lifted I sent the keycode twice ie the same character in place of the null then it was switched off.
Both fixes also worked on the original word processor program. The special shift key had only worked by a quirk in the original program – the character I sent changed a mode which, as a side-effect, cleared the shift special. I had never resolved how to clear the “set margin mode” but I found the same trick worked. It is cleared by sending the set margin code twice.
With these fixes, CP/M was useable – but only with the few disks that worked. I did find that the copy program could be used to format disks – a vast improvement on the word processing program, which had no such facility.
This gave me the kick i needed to address the screen.