Serial communication with bytes (0x00 problem)

Question

I have a problem while using serial communication for USB CDC. I'm working on embedded STM microcontrollers and i wanted to pass binary data with pySerial.

I wanted to send binary codes directly but I am blocked by this 0x00.. My problem is when i want to send 0x00 byte, the next bytes seems to be ignored..

Here's the python script:

towrite = [ 0xFF, 0xx00 \xFF ] 
nbSend = s.write(b'\xFF\x00\xFF')
print(nbSend)                                 #Displaying 3 here, that means 3 bytes are successfully sended

Then the embedded script:

//Interrupt function that receive the data from serial com
static int8_t CDC_Receive_FS(uint8_t* Buf, uint32_t *Len)
{
  /* USER CODE BEGIN 6 */
  USBD_CDC_SetRxBuffer(&hUsbDeviceFS, &Buf[0]);
  USBD_CDC_ReceivePacket(&hUsbDeviceFS);

  char buffer[64];

  sprintf(buffer,"Length=%lu / Word=%c%c%c ",(unsigned long)*Len,Buf[0],Buf[1],Buf[2]);
  debugPrintln(&huart2, buffer)  //Function to print on serial to debug
  //Here that print "Length=3 / Word=ÿ "


  return (USBD_OK);
  /* USER CODE END 6 */
}

As you can see, the second and ultimate characters (0x00, 0xFF) are not taken into account even if the number of bytes received is good... Any advice?

Answer 1

It's the debugging that's not working, but the data transfer is just fine.

sprintf(buffer,"Length=%lu / Word=%c%c%c ",(unsigned long)*Len,Buf[0],Buf[1],Buf[2]);

The second %c puts an actual NUL byte in the buffer, so everything else after it is ignored by the debugPrintln .

For testing, change to:

sprintf(buffer,"Length=%lu / Word=%02X %02X %02X",(unsigned long)*Len,Buf[0],Buf[1],Buf[2]);

and see if it shows you all the bytes.