I've decided to look at further enhancing the work from Traumflug - I love Gen7, but I'd like to have a few more options open to me for dual extrusion.
I've got a completely jumperless design based around an STM32L4 MCU (just because I happen to have a smidgen of familiarity with it, and I think I can probably get Marlin going on it). I like to seperate my concerns, so the plan is that this will be driven by something else, so a good old USB connection, I am contemplating adding support for a direct PI connector (I've got a 5V step down in board that should be good for up to 3A and could back power the Pi, and I've gone for 3.3V as native power on the MCU - just because). As I've gone for an STM, it has USB on board, so I should be able to interface directly that way (may need to register for that), but if I add a UART interface for the Pi, then it may not be necessary. Going 3.3V means there's no need to level shift to the Pi.
I've enhanced what's from Gen7 with an extra stepper, solid state selection of stepping values (all the same) but also support for TMC SPI interface. 2 fixed outputs and 2 PWM outs, and a couple of extra end stops for filament sensors/Z probe. I'm tempted to add support for a PINDA probe, which I think I have enough pins for.
V-In should be tolerant up to 28V.
Should I make a production run?
Have I missed anything obvious?
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