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USART on STM32F4 using Arduino board

Question asked by sergent.edouard on Aug 21, 2015
Latest reply on Aug 23, 2015 by Clive One
NOTE: edited by moderator on Oct 6th, 2016
Hello everyone,

I just received my stm32f4 discovery board yesterday and it works well :). I managed to run a LED blinking example. I now want to display some results in a serial communication. I am trying to interface an Arduino Uno with my stm board. I found an example on the internet :
[[this link/image has been flagged as malicious by our security scan software and has been deleted]]
but I am not able to make it works properly.

I put wires between TX of Arduino - PB7 and RX of Arduino - PB6. Here is my Arduino code :
#include <SoftwareSerial.h>
SoftwareSerial gprsSerial(0, 1);
 
void setup() {
  // initialize serial communication at 9600 bits per second:
  gprsSerial.begin(9600);
  Serial.begin(9600);
}
/* Loop() */
void loop() { 
  // Si des données sont disponible en lecture
  if(gprsSerial.available() > 0) {
   
    // Lecture d'un octet depuis le port série
  int c = gprsSerial.read();
          Serial.println(c);}
}

When I click on the reset button of the stm board, I receive these 4 numbers on the Arduino terminal : 255;28;0;252

I don't know how to deal with these numbers. It represents Byte but what is the relation ?
Moreover, If I change the sentence to display.
USART_puts("b");
I still have 4 numbers : 255;224;0;252

Do you know what it means ? Normally, I should receive more numbers for the sentence than the char.

Thank you very much for your help.

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