VFD Compatibility?

[Gibs (Tanner)]

@CthulhuLabs

Can you expand on this? What is the issue?

The SO5’s PWM signal from the spindle port does not work nice with VFD’s without additional signal conditioning. You can still get an unaltered PWM signal from the MOSI port on the board.

You can read more about it in this thread:

Pinout on warthog controller Shapeoko 5 pro

Looks like U3 causes increased rise time both times they feed through the chip. Possibly a counterfeit TI chip as the specifications for the real chip is a max of 12.5ns from low to high with a max propagation delay of 50ns. It is also possible that C140 is making the problem worse. U3 pin 5(from 328p MOSI pin), 33.81ns rise: [IMG_1504] U3 Pin 13, 2.26us rise: [IMG_1505] U3 Pin 11(to Spindle PWM Pin), 13.94us rise: [IMG_1506] It’s worth noting that these findings are intriguing, partic…