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Lab06 - Nucleo Communication stack

The communication between Nucleo board and PC uses RS232 data link. The C language allows you to use multiple levels of abstraction as it is described in the following figure. The operating system (OS) level uses open, write, read, close function and the C standard library uses fopen, fwrite, fread and fclose functions. While the C standard library provides the same behavior on the all platforms the OS level can vary with implementation.

Recieve by Interupt

  • In this session, we will receive data in an non-blocking manner using the interrupts

uint8_t Rx_char[1];
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart) 
  HAL_UART_Receive_IT(&huart2, Rx_char, 1); 
int main(){
  HAL_UART_Receive_IT (&huart2, Rx_char, 1);
  while (1)

  • The function HAL_UART_RxCpltCallback is called every time that board receives a data from UART. The execution of this function does not stop while loop from going on.

The NUCLEO stack

  • The NUCLEO side is expected to wait for the characters and add each received character to a stack. The reception management of the characters requires a data structure which is implemented as:

#define cRECV_BUFF_MAX 10
typedef struct tRecvBuff
  char chArrRecvBuff[cRECV_BUFF_MAX];
  int iCnt;
} tRecvBuff;
tRecvBuff oRecvBuff;

The structure is initialized as:

  oRecvBuff.chArrRecvBuff[0] = 0;
  oRecvBuff.iCnt = 0;  

And the reception is performed through:

while (1) 
         if (Rx_char[0] != prev_Rx_char[0]){
                 prev_Rx_char[0] = Rx_char[0];
                 oRecvBuff.chArrRecvBuff[oRecvBuff.iCnt] = (char) Rx_char[0];
                 HAL_UART_Transmit(&huart2, oRecvBuff.chArrRecvBuff , sizeof(oRecvBuff.chArrRecvBuff) ,10);
                 HAL_UART_Transmit(&huart2, enter  , sizeof(enter),10);

  • To see the complete project, download the files in link lab06_.zip.


  • Define the mechanism of a “complete” command detection (based on '\r' and '\n').
  • Define the mechanism of buffer clearing after successful processing of the received command.
  • Detect the “LED ON” and “LED OFF” commands to be able to control the User LED of the Nucleo board.
  • Detect the “BUTTON?” command to be able to read the User Button state.
courses/be5b99cpl/labs/lab06.txt · Last modified: 2021/10/23 00:04 by amjadara