So, did you wire the 5V J4 with the resistor to -J17 as a voltage divider?
On my diagram the 5V J4 is wired to the +J17.
The resistor pulls up the output of Mosfet Q4 (pin2*) to 5V, its not a voltage divider. The schematic does not show if pin 2 is the + or the - pin on the “Hotbed” mosfet. My guess is the + on J17 is connected to VBB (12V) not the mosfets output. I think your right the - pin is the output you want.
My screw up #1: in that I did not notice on your drawing that you have a black wire connected from J17 to the laser driver board, that is wrong. Only one wire will be connected from J17 to the TTL input of the driver.
You can verify if the correct pin is the - or the + of J17 by tracing and verifying if it is connected to the drain of Q4. You can also measure the voltage on the + pin with power on and nothing connected to it. If its connected to VBB it will read 12vdc and this is NOT the pin you want.
I do not know for certain but I think the + is probably connected to the boards VBB (+12V) so the - is the correct connection.
Do not connect anything to the other pin on J17. [I assume that is the + pin]
*My screw up # 2: J17 does not have 4 pins . It has two and they are labeled 1 and 2 in the schematic. I did get the mosfet # right as Q4.
When operating properly you should get an average voltage from J17 that is roughly proportional to the S value where: 5V is max (100%), 2.5V is 50% etc.
So i changed it and now i can control the laser power, but in wrong direction. S0 = Full and S300=off
Does that mean i have to use P1.23 instead of P2.5?
No continue using P2.5, you should just be able to invert the P2.5 pin (J17) in the config file. For smoothie it’s the “!” symbol.