UART problem with KL26Z128

rafaeldalazen — Thu, 09 Jul 2015 15:29:27 GMT

Hi,

I'm dealing with a UART problem, I can't transmit any data from UART1 (which share the same pin with OpenSDA on KL26Z128 board) to the serial port terminal. I must not use interrupt mode, only polling; and I'm testing the code forcing it to transmit the character '5' (0x35 in ASCII), but without success. The UART_D buffer remains equal to 0x00 all the time. I thought that the problem could be the baud rate (115200 bps) , but the UART_TX (PTC4) signal is a normal UART signal.

The UART's code follows below:

void uart1_init (void){

SIM_SCGC5 = SIM_SCGC5_PORTC_MASK;

SIM_SCGC4 = SIM_SCGC4_UART1_MASK;

SIM_SOPT5 |= SIM_SOPT5_UART1TXSRC(0);

PORTC_PCR3 = PORT_PCR_MUX(0x3);

PORTC_PCR4 = PORT_PCR_MUX(0x3);

UART1_BDH = 0x00;

UART1_BDL = 0x1A; /* SBR = 26 */

UART1_C1 = 0x00;

UART1_C3 = 0x00;

UART1_C4 = 0x00;

UART1_S2 = 0x00;

UART1_C2 |= UART_C2_TE_MASK;

}

void uart1_send (int data){

while(!(UART1_S1&UART_S1_TDRE_MASK) && !(UART1_S1&UART_S1_TC_MASK));

UART1_D = data;

}

int main (void){

uart1_init();

while(1){

uart1_send( 0x35 );

}

Is there any error on code?

Could someone give me a clue?

Thanks in advance,

Rafael

Re: UART problem with KL26Z128

EarlOrlando — Mon, 02 Nov 2020 13:16:53 GMT

Helo Rafael,

You need to enable the transmitter:

UART1_C2 |= UART0_C2_TE_MASK;

You can take a look into this thread to see how the baudrate is calculated, especially the information that I have copied below.

In the reference manual you can see that the baud rate is generated as follows:

So the SBR value can be calculated:

SBR[12:0] = UART Module Clock / (16 * Baud rate)

The UART Module Clock is the bus clock which does not seem to be configured. By default the Bus Clock is 20.97152 MHz, so:

SBR = 20.97152 MHz / (16 * 115200) = 11.3777

I suggest to change the bus clock to 48 MHz, it will produce a more accurate baud rate:

SBR = 48 MHz / (16 * 115200) = 26.0416

Best regards,

Earl.

topic Re: UART problem with KL26Z128 in Kinetis Microcontrollers

UART problem with KL26Z128

Re: UART problem with KL26Z128