Oh I was going to mention Octoprint...
Part of the point of making the printer self-contained was to also include a Raspberry Pi to run Octoprint which is basically a 3D printer server. It has a nice web UI and you can send prints to it directly from Cura, run a web cam etc. All very useful.
Unfortunately, it is not useful and has left my printer less good than before I started
The first few prints were great, but I soon found that when printing from Octoprint (rather than SD card) that the printer would slow down and stall when printing small curves. It can't effectively print a circle smaller than 5mm, and with the Hypercube held together with mostly M3 hardware, thats a big problem. As is par for the course, the software developer blamed the hardware, but I didn't see this problem with Cura. Basically Octoprint can't feed the Gcode to the printer fast enough on USB for doing small curves, and so it just slows down to a crawl. Its a well documented problem on Github but the developer just blames everything other than their own code.
In a rather misguided attempt to improve the situation (and to prevent a bunch of CR-10 specific errors in Octoprint) I upgraded the printer firmware. Bad move
Now print quality is worse than it was before, it struggles on most circles, and to add insult to injury, there is no option in Cura to save the existing firmware so I can't even go back to what worked.
So, the next step is Klipper firmware. This replaces the Creality-specific Marlin firmware on the board and couples it with a compute component running on the Pi. Rather than sending Gcode over the USB, Klipper on the Pi interprets the code and simply sends move instructions down the USB to the Klipper firmware on the control board which is supposedly much faster. I might buy a spare CR-10S control board before I try this!
The downside is that you still have to use Octoprint to control Klipper. I rather resent that since it was Octoprint that buggered the printer in the first place, but Klipper has a virtual SD card in the Pi's memory so it should (!) all be nice and slick. So I'm told anyway.
If it works then its a good alternative to an expensive Duet board. I can buy a cheap MKS Gen board for the controller, and do the compute on a Pi3 and control it from a browser using Octoprint.
To be continued...