4 axes + pwm spindle

billykid wrote:

I doubt whether to use for the 3 mpg (feedrate, spindle_override, pendant) the input hardware encoder, or via gpio and Halui

If you have enough encoder modules in your firmware then you might as well use the hardware encoders. If you want to use the software encoders then you probably need to run a base thread and also read the GPIO and encoder in the base thread. That is quite a lot of CPU overhead.

You can just ignore the index connection. The encoder will still work.
In fact you can also ignore the B pin if you put the encoder in counter mode. (but then it will only count up, not down)

I suspect I might not be answering the question you are asking. Could you try rephrasing it if not?

You can't really use the unused pins of an active encoder, but you can use the unused pins of inactive encoders simply by reducing the num_encoders parameter in the config string. The pins all then become GPIO.

If you were very short of pins you could use the index pin as a general purpose input, with the drawback that you could never try to use the index on that encoder normally. The encoder pins are still visible as GPIO inputs.