Arduino for STM32

I'm using STM32F401RE, with core Arm Cortex-M4

How can I pass through the serial ports an arduino number to the STM32 F401RE? Using the Arduino IDE? For now I have done this: (i should do all this using just the arduino ide) Code Arduino (TX) int valueTX=5; void setup() { Serial.begin(9600); } void loop() { Serial.print(valueTX); } Code STM32 F4...