How to use UART receive data for further processing rather than just echoing in embedded C?

Question

Here is the code from my test environment. it simply replies back (echo) the entered data to the terminal application where it is connected through a Serial Port. So far so good.

Now, I need to use that data and process as per the requirements/protocol. But, I am struggling to consume the data UART0Buffer as I expected. (The variable UART0Buffer is populated in the UART Interrupt)

I send e.g. "7E0007AA010203040506CC" from the terminal and the code replies back this to the terminal application in an order in four steps for some reason;

1 by Process #1

37

2 by Process #2

00

3 by Process #1

30 30 30 37 41 41 30 31 30 32 30 33 30 34 30

4 by Process #2

A1

As you can also notice that the data replied (echoed) is not identical with what I send from the terminal.

And furthermore, if I remove line "Process #2" completely, I can get a proper echo;

37 45 30 30 30 37 41 41 30 31 30 32 30 33 30 34 30 35 30 36 43 43

What am I really missing here?

int main()
{
    SystemInit();       /* Clock and PLL configuration */   
    UARTInit(0, 57600); /* baud rate setting */

    while(1)
    {
        if ( UART0Count != 0 )
        {
            LPC_UART0->IER = IER_THRE | IER_RLS;            /* Disable RBR */

            UARTSend( 0, (uint8_t *)UART0Buffer, UART0Count ); // Process #1

            UART0Count = 0;

// I need to call a function here in order to process data in UART0Buffer
// like checking/using STX, CHKSUM and DATA.

            // A test, if I can manage to use the data in pieces
            UARTSend( 0, (uint8_t *)UART0Buffer[0], 1); // Process #2

            LPC_UART0->IER = IER_THRE | IER_RLS | IER_RBR;  /* Re-enable RBR */
        }
    }
}

void UARTSend( uint32_t portNum, uint8_t *BufferPtr, uint32_t Length )
{
  if ( portNum == 0 )
  {
    while ( Length != 0 )
    {
      /* THRE status, contain valid data */
      while ( !(UART0TxEmpty & 0x01) ); 
      LPC_UART0->THR = *BufferPtr;
      UART0TxEmpty = 0; /* not empty in the THR until it shifts out */
      BufferPtr++;
      Length--;
    }
  }
}

EDIT: As dude has already explained the wrong use of "Process #2", please ignore it. It somehow breaks things. However, my issue persists. Although I can get an echo by "Process #1", I couldn't manage to read and use the data!?! Any pointers would be greatly appreciated.

EDIT:

Receiving:

void UART0_IRQHandler (void) 
{
  uint8_t IIRValue, LSRValue;
  uint8_t Dummy = Dummy;

  IIRValue = LPC_UART0->IIR;

  IIRValue >>= 1;           /* skip pending bit in IIR */
  IIRValue &= 0x07;         /* check bit 1~3, interrupt identification */
  if ( IIRValue == IIR_RLS )        /* Receive Line Status */
  {
    LSRValue = LPC_UART0->LSR;
    /* Receive Line Status */
    if ( LSRValue & (LSR_OE|LSR_PE|LSR_FE|LSR_RXFE|LSR_BI) )
    {
      /* There are errors or break interrupt */
      /* Read LSR will clear the interrupt */
      UART0Status = LSRValue;
      Dummy = LPC_UART0->RBR;       /* Dummy read on RX to clear 
                            interrupt, then bail out */
      return;
    }
    if ( LSRValue & LSR_RDR )   /* Receive Data Ready */            
    {
      /* If no error on RLS, normal ready, save into the data buffer. */
      /* Note: read RBR will clear the interrupt */
      UART0Buffer[UART0Count] = LPC_UART0->RBR;
      UART0Count++;
      if ( UART0Count == BUFSIZE )
      {
        UART0Count = 0;     /* buffer overflow */
      } 
    }
  }
  else if ( IIRValue == IIR_RDA )   /* Receive Data Available */
  {
    /* Receive Data Available */
    UART0Buffer[UART0Count] = LPC_UART0->RBR;
    UART0Count++;
    if ( UART0Count == BUFSIZE )
    {
      UART0Count = 0;       /* buffer overflow */
    }
  }
  else if ( IIRValue == IIR_CTI )   /* Character timeout indicator */
  {
    /* Character Time-out indicator */
    UART0Status |= 0x100;       /* Bit 9 as the CTI error */
  }
  else if ( IIRValue == IIR_THRE )  /* THRE, transmit holding register empty */
  {
    /* THRE interrupt */
    LSRValue = LPC_UART0->LSR;      /* Check status in the LSR to see if
                                    valid data in U0THR or not */
    if ( LSRValue & LSR_THRE )
    {
      UART0TxEmpty = 1;
    }
    else
    {
      UART0TxEmpty = 0;
    }
  }

}

How to use UART receive data for further processing rather than just echoing in embedded C?

Answers (1)

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