ARM, RISC-V контроллеры

Сейчас заработало! Нашел пример

https://os.mbed.com/users/hudakz/code/STM32F103C8T6_Hello/

#include "mbed.h"

Serial pc(PA_2, PA_3); // TX, RX
DigitalOut myled(PC_13); // on-board LED

int main()
{
while(1) {
// The on-board LED is connected via a resistor to +3.3V (not to GND).
// So the LED is active on 0
myled = 0; // turn the LED on
wait_ms(200); // wait 200 millisecond
myled = 1; // turn the LED off
pc.printf("Blink\r\n");
wait_ms(1000); // wait 1000 millisecond
}
}