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FreeRTOS +UART TX DMA+ UART RX Size variant buffer

Question asked by sbm on Nov 22, 2016

Hi guys, I'm facing out some problems and i wonder if some of you can give some of your wisdom.

Here are some inputs:

       
  • MCU: STM32L053 (Host)
  •    
  • GSM Module: handles GSM network connecctions and notifify via UART the MCU. It also receives MCU commands.
  •    
  • UART-USB converters: They let me monitor what happens in each pin (RX and TX) by means of hiperterminals
  •    
  • UART TX +DMA for transmissions of AT commands
  •    
  • UART  RX for reception of messages of different sizes.
  •    
  • I don t use the hal library for the uart IRQ. (unfortunately, ST doesn't provide std firmware neither! So i ve )

My purpose is as follows:
trigger 2 different threads depending on a received buffer pattern. For this, i will use a preemptive scheduler (FreeRTOS V8.2.3+ cmis os interface).

Here are some code snippets with brief some brief explanation:

 

static void EmergencyButtonEventProcess(void)

 

{

 

    DelSMS();

 

}

 void DelSMS(void)
 {
      Send_AT_Command(eDelete_All_Sms);

 }

static void Send_AT_Command(AT_CommandId_tE  Cmd_Id_tE)
{
...
      U8 source[MAX_SIZE_FOR_BUFFER]; 
      switch(Cmd_Id_tE)
      {
            case eCheck_Gsm_Module:
                  strcpy(source, CHECK_GSM_MODULE);
                  sizeOfBuffer = LibTyp_StrLen(&source);
                HUart_Transmit( HUart_eUart2, source, sizeOfBuffer );
                  break;
            case eRead_SMS:
                  strcpy(source, READ_SMS_COMAND);
                  sizeOfBuffer = LibTyp_StrLen(&source);
                HUart_Transmit( HUart_eUart2, source, sizeOfBuffer );
                  break;
            case eDelete_All_Sms:
                  strcpy(source, DELETE_ALL_SMS_COMAND);
                  sizeOfBuffer = LibTyp_StrLen(&source);
                HUart_Transmit( HUart_eUart2, source, sizeOfBuffer );
                  break;
            default:
                  break;
      }

}

 

 

 


These functions are called when a button is pressed  and after a debounce time has passed. I used the IRQ of a GPIO and IRQ of a timer.
 
When the button is pressed more than 5 seconds a command is sent to the GSM module and this one responds with an OK. The transmition is done with a uart peripheral of the MCU and DMA. All works correctly and as expected. In this case i have not used any of the OS services but maybe in the future, i would sync with a semaphore. I don't think this is necessary.


 

void USART2_IRQHandler (void)

 

{

 

   //Store DR

 

  //Detect patern and store it in appropiate buffers...
if(TX_RX_Buffer_Flag_tb ==TRUE)
{
... //more pattern tests...
      //store TX_RX_Buffer[] 
      TX_RX_Buffer_Flag_tb =FALSE;
      osSignalSet(ThreadId_2, BIT_2 );
}

if(RX_Buffer_Flag_tb==TRUE)
{
... more process
   //store RX_Buffer[]       
   osSignalSet(ThreadId_1, BIT_1);
}

 

   

 

}

 


In the UART IRQ, i fill up 2 buffers depending on the start of the message. Basically, we have 2 types:

       
  • TX_RX_Buffer[] = "AT+something \n" pattern corresponds to a answer of the gsm module after a command has been sent.
  •    
  • RX_Buffer[] = "\r  something \n" pattern corresponds to a notification of the gsm module. 

A event flag is set and notified to the OS. A related thread (depending on the buffer patern detected) has to be triggered 

 

static void Thread1_RX_Buffer(void const *argument)

 

 {

 

      osEvent event;

 

      for(;;)

 

      {

 

        event = osSignalWait( BIT_1, osWaitForever);

 

        if(event.value.signals == BIT_1)

 

        {

 

            Send_AT_Command(eRead_SMS); //UART Transmit with DMA is called

 

           }

 

}

 

 

 

static void Thread2_TX_RX_Buffer (void const *argument)

 

{

 

 

 

  (void) argument;

 

  osEvent event;

 

  RelayId_tE Id_tE;

 

 

 

  for(;;)

 

  {

 

    event = osSignalWait( BIT_2 , osWaitForever);

 

    if(event.value.signals == (BIT_2 ))

 

    {

 

        Send_AT_Command(eMakeCall);  //UART Transmit with DMA is called

 

    }

 

  }

 

}

 


Here the Threads are triggered as expected. The problem is that only 3 characters are transmitted and the rest are incoherent (i.e
 AT+Cÿÿÿÿ[02][00]). 
On the other hand, the same transmission function is called when the button is pressed and all is ok.
 
I think that the tick interrupt related to the OS corrupts the UART DMA transmission. How can i sort this out ? Any suggestions? 


PS: Any suggestions are welcome concerning the design/implementation. There are still some improvements to do like copy the buffer for deferred processing ....


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