There's something I don't understand about the RATOS 4028 FAN guide.

Hi I'm trying to follow the Ratos guide to prevent the fan from running when the power is turned on. My boad is BTT Octopus v1.1 Does the following explanation mean to connect to PA9? or I have to connect other pin ? This is a safety feature of server fans, they will always run at 100% until they get a PWM signal. It's a bit annoying for 3d printer use, but there's a way around that. You can use the negative terminal of a spare heater port to only power the fan when the board is booted, by connecting the black wire (gnd) to the negative terminal of the heater port. Since these fans run high amperages, it's important that we use a pwm port backed by a properly rated mosfet, which is why the heater ports are perfect. Let's say we connect the gnd wire to the second heater of our board which is controlled by the pin PA9 (made up pin name, look up the correct pin in your boards pin diagram), the configuration would be the following: