Issue while receiving data into "UART2_D "register

[priyankavorugan]

Hi,

I am using MKL17z series microcontroller in my project.I am using UART2 for serial receive and transmit.
I am using seperate ISR for transmit and receive.I am able to generate the interrupt for transmit and receive.

But my problem is i can transmit the data and can check that in one of my utility and can see that in uart2_d reg.

But i am unable to receive the data sent by the utility and i cant even see that data in uart2_d reg.

uart2_d register is used fo both transmission and reception??

[mjbcswitzerland]

Hi

The data register is WRITE for transmission and READ for reception. This means that you will never be able to see the value that you write to it by reading it back.

Regards

Mark

http://www.utasker.com/kinetis.html for quality Kinetis firmware

[priyankavorugan]

Hi,

I have taken a local vaiable and I try to read the UART2_D  register value into that  variable( rx_buffer = UART2_D).
but the i cant see any value in that variable.

So,can I read the data from UAT2_D reg??

What i have noticed is,suppose if i Transmit 10 ,i can read back the same value i.e 10.But i cant read the value that i sent using utility.

I have implemented as shown below.

void UART2_handler(void) 
{

     if ((UART2_S1&UART_S1_TDRE_MASK))     //transmit buffer is empty,write D reg.
    {
          if((UART2_S1&UART_S1_TC_MASK))
         {
            BT_MANAGER_Tx_ISR();
         }
   }

   if((UART2_S1 & UART_S1_RDRF_MASK))       //Receive buffer is full,read D reg.
   {
      BT_MANAGER_Rx_ISR();
   }

}

[Robin_Shen]

Have you try to disable the UART2_C2[TIE] and UART2_C2[TCIE] and then read the data from UAT2_D reg?

void UART2_handler(void) 
{

   if((UART2_S1 & UART_S1_RDRF_MASK))       //Receive buffer is full,read D reg.
   {
      rx_buffer = UART2_D;
   }

}

And make sure you are not using '38.5.6 Loop operation' mode.

I test the uart interrupt demo in SDK_2.2_FRDM-KL27Z with FRDM-KL27Z board. (...SDK_2.2_FRDM-KL27Z\boards\frdmkl27z\driver_examples\uart\interrupt)

I can read the data from UAT2_D reg after I send data using UART Terminal port.

You can download and test that demo in SDK_2.2_MKL17Z.

Best Regards,

Robin

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[mjbcswitzerland]

Hi

When you read the data register you read the last received data value. This "may" be equal to the last transmitted value in case the rx 'sees' the tx line.

To get past this stage I recommend letting the code configure the UART then pausing the debugger. Now display the UART registers in the debugger's IDE and experiment with writing values to the data register. If the UART is operating correctly you will see these being sent to the TXD line. You can then monitor what happens with the value read from the data register and also experiment with ready after there has been a real character reception. This will allow you to understand the behavior and also verify the HW. Once you have understood the operation you can then adapt the code accordingly.

Regards

Mark