Marlin: Questions about pin output during Marlin startup.

[ghost]

Hello.
I am using Berd-Air to cool the PLA.
Yesterday, I replaced the air pump motor used with Berd-Air.
The new motor is a PWM-controlled brushless motor called A3650.

The replacement went well.
Motor is operating normally by connecting PWM wire to servo pin and assigning FAN_PIN.
However, after the power is turned on, the motor will run with full power until the Marlin startup process is completed.
The full power motor is very noisy.
Is there a way to specify the output state of a particular pin while Marlin's logo is displayed on the LCD?

P.S.
I am using Arduino Due.

[thinkyhead]

Hmm. Try moving this line in setup() down…

  servo_init();             // Initialize all servos, stow servo probe

…after…

  #if ENABLED(SHOW_BOOTSCREEN)
    lcd_bootscreen();
  #endif

[ghost]

Thank you for your reply.
I tried it, but there was no change in the motor.
I do not know if it is related to this problem, but while flashing marlin, the motor is rotating at full power.

[AnHardt]

A hardware reset sets all pins to a defined state. (For the AVRs that is 'input' with 'pullups low'.) If your motor is on in this state there is nothing we can do against that until the pin is initialized by Marlin. Especially we can't initialize it as log as the bootloader is running.
In that case only a hardware inverter does help. (That's why 'RAMPS FE V1' is called dangerous.)

[ghost]

Indeed I understand.
I will insert a suitable switch for the PWM wire.
Thank you.

[MrAlvin]

@JXPA Like it has been said, then the default state (power on state / reset state) of the Atmega chips are input state. So a pull-down resistor at the power-mosfet (or in your case a motor-on pin), will keep it from being activated.

However, the Due default state of the pins is, with the internal pull-up resistor to be enabled. According to the datasheet, this pull-up resistor has a value between 50K and 150K, but is typically around 100K.

So one way to make the default pin state different, is add an inverter between the Due pin and the motor controller on-pin.

Another way is; to add a stronger pull-down resistor. I have had good results with adding a 4K7 pull-down resistor to the Due pin(s), where I need the LOW signal state to be the default state on the pin.

A third way to change the default state of your motor-on signal is, to add a switch between the Due pin, and the motor-on signal pin.
You should however still check to see, if the motor controller already has a pull-down resistor on the motor-on pin off the motor controller. Otherwise you need to add such a pull-down resistor, even when adding a switch between the Due pin and the motor controller.

It is common practice that all input pins should have a pull-down or a pull-up resistor added to them. Otherwise they will be floating, and they will have a tendency to pick up noise when you put something like a hand or finger close to them.
Many an electronics novice has had this experience about their input pins, and have sometimes spent days trying to figure out why a certain design would not behave in a predictable way.

[ghost]

@MrAlvin - I appreciate your help.
Solved by installing a 1k pull-down resistor at the servo0 pin.