SDK 2.1 UART Rx Overflow handling bug

[paulsandys]

I think there's a logical bug in fsl_uart.c

/* If RX overrun. */

if (UART_S1_OR_MASK & base->S1) {
/* Read base->D to clear overrun flag, otherwise the RX does not work. */
 while (base->S1 & UART_S1_RDRF_MASK) {
      (void) base->D;
 }

The "while (base->S1 & UART_S1_RDRF_MASK)" creates a problem when the routine gets preempted by another interrupt. The RDRF can be set again, causing the routine to eat up extra bytes and/or generate additional Rx OR interrupts. After removing the while loop and reading "(void) base->D;" exactly once, the problems go away.

[Alice_Yang]

Hello Paul,

Which chip do you used?

I randomly check one SDK package (FRDM-K22),

it just read D once :

BR

Alice

[biafra]

Hi Alice_Yang‌,

It's the same in the latest SDK for TWR-K65F180M (2.4.1 2018-09-14).

Many thanks

Biafra

[NicolasP]

Hi,

Same problem with SDK 2.4.1 and K22FN51212

Best regards,

Nicolas

[paulsandys]

FRDM-KL25Z

[Alice_Yang]

Hello ,

Thanks for your sharing , I will report it to the SDK team.

And I recommend you can use the UART driver file of FRDM-KL26.

I also attached it for you.

Hope it helps

Alice

[paulsandys]

I've wrote my own IRQ handler.

It would be very useful if the UART async driver could callback after receiving "special" character specified in the xfer structure, similar to SPI. (I.E.  NewLine, CarriageReturn, NULL or whatever)