Control classic Servo Motor with STM32 and Mbed library

Question

I'm using STM32 F401RE board and i'm trying to do a very simple thing. I want to control a servo (0-180). The problem is that it looks like it doesn't respound to my commands.

#include "mbed.h"

PwmOut myServo(D9);

int main() {
    myServo.period_ms(20);    

    while(1)
    {
        myServo.pulsewidth_ms(1);
    }
}

The Servo Motor i'm using. At the beginning i though something is wrong with my board pinout or pinout meaning , but it seems like D9 is the same with PC_7 . My servo is properly installed and is supplyed by 5V source. I tried many tutorials i've found online but no one worked. This is the class with all methods.

If i generate the same PWM with an oscilloscope it does work.

Answer 1

I figured out what the problem was. I didn't had all grounds connected together because i was powering the STM32 via USB. When i was testing, the STM was connected to PC so the ground of the servo was different from the ground of the STM32.