Marlin 2.0 relative extrude on external signal

Hi,

I have a MKS gen1.3 board with Marlin 2.0 on it, as the title, I want the extruder motor to start extruding when an external signal is on.
I only have 1 exturder, so i'm thinking of using the pins for E1 as input pins.
I'm looking at the board diagram below, and the pins for E1 that I can use are 30, 34,36



So my thought is, use relative extrude and a loop so that it keep looping the relative extrude command when the signal is on.
So would this following code work? and where should I insert this in the marlin firmware?

while(30){
G1 E1.5 F1500
}

and the external signal currently outputs 24v, I'm assuming I need to step it down to 5v/3.7v?

thanks in advance.

Edited 1 time(s). Last edit at 09/10/2019 12:41AM by evo85210.

You forget how fast the processor really is... (compared to slow human perception)

that will flood the command buffer with thousands of G1 commands per second.

Hi this thread is of interest to me. I'm trying to do the same thing.

evo85210, did you succeed after all?

Regards,

JFCh