I expect the Arduino to be easier, was in a hurry to see some pwm output, so I started with it.

Note that I'm testing with PB4 which after checking the pinout (at least), does support the hardware pwm functionnality, I'm not interested in any soft pwm, and I also expect libraries to do the necessary configuration for me.

new Arduino Project

• Create the project

pio init --board bluepill_f103c8 --project-option="framework=arduino"

• Add the main.cpp

#include <Arduino.h>

void setup()
{
  pinMode(PC13, OUTPUT);
  pinMode(PB4, PWM);  
}

void loop()
{
  analogWrite(PB4,0);
  digitalWrite(PC13, HIGH);
  delay(200);
  analogWrite(PB4,255);
  digitalWrite(PC13, LOW);
  delay(1000);
}

Result = Fail !

Fail !It keeps hanging, no LED plinking, well, you could debug it, but no, welcome to Arduino, I do not have serial connected to my board (early dev phase) and USB is out of flash size.

After some googling I found another API for PWM :

  pwmWrite(PB4,0);
  pwmWrite(PB4,200);

Result = Fail !

Is this a framework supposed to be easier for newbies ? Not even the simplest peripheral has a unified API, why do we say that the STM32 is supported by this framework then, if I have to manipulate registers to get my pwm to run ?

new Mbed Project

• Create the project

pio init --board bluepill_f103c8 --project-option="framework=mbed"

• Add a main.cpp

#include "mbed.h"

DigitalOut myled(PC_13);

PwmOut my_pwm(PB_4);

int main() 
{
    my_pwm.period_ms(20);
    while(1) 
    {
        my_pwm.write(0.5);
        myled = 1; // LED is ON
        wait(0.2); // 200 ms
        my_pwm.write(0.0);
        myled = 0; // LED is OFF
        wait(1.0); // 1 sec
    }
}

• research steps, googling "mbed pwm", first hit had a note to go to the latest pwm API page, and there, surprisingly, a simple example !!! not like all supposedly professional APIs where of course, who needs simple examples.
• compile and flash

>pio run
>pio run -t upload

Result = Success

The LED is blinking, the quick measures show correct behavior of the PWM pio, did not check it with oscillo yet, but sounds correct.

Conclusion

Arduino (-1)

Mbed (+1)

PlatformIO (+1)

The context of this project is the STM32 Bluepill, Arduino might be better for 8bits or AVR, but for the Bluepill, mbed defeats arduino on its own field of excellence which is the simplicity of use for the very simple peripherals. PlatformIO here again shows how easy it is to compare different frameworks by still using the same commands.