UART tansmission erroe when baud rate above 9600 bps?

hg-chen · ‎2007-04-19

Posted on April 19, 2007 at 10:08

hg-chen · ‎2007-04-19

Posted on April 19, 2007 at 09:42

STR711FR2 us used,

when setting UART at baud rate 9600 bps,it works fine,

but above 9600 bps, transmission data received become scramble!

any advise?

setting as below,

//----------------------------------------------------------------Uart2 config

/* GPIO peripheral configuration -------------------------------------------*/

/* Configure the GPIO pins */

GPIO_Config(GPIO0, UART2_Tx_Pin, GPIO_AF_PP);

GPIO_Config(GPIO0, UART2_Rx_Pin, GPIO_IN_TRI_CMOS);

/* UART peripheral configuration -------------------------------------------*/

/* Configure the UART X */

/* Turn UART0 on */

UART_OnOffConfig(UART2, ENABLE);

/* Disable FIFOs */

UART_FifoConfig (UART2, DISABLE);

/* Reset the UART_RxFIFO */

UART_FifoReset (UART2 , UART_RxFIFO);

/* Reset the UART_TxFIFO */

UART_FifoReset (UART2 , UART_TxFIFO);

/* Disable Loop Back */

UART_LoopBackConfig(UART2 , DISABLE);

/* Configure the UART0 as following:

- Baudrate = 115200 Bps

- No parity

- 8 data bits

- 1 stop bit */

UART_Config(UART2,19200,UART_NO_PARITY,UART_1_StopBits,UARTM_8D);

/* Enable Rx */

UART_RxConfig(UART2 ,ENABLE);

kleshov · ‎2007-04-19

Posted on April 19, 2007 at 10:08

Given a certain APB clock frequency, possible baud rates are limited to a series of values:

BaudRate = Fapb / (16 * UARTn_BR), UARTn_BR = 1, 2, 3, ..., 65535

See Reference Manual for details.

When the difference between baud rates on the transmitting and receiving sides exceeds a certain limit, errors in reception occur.

In order to be able to precisely generate standard baud rates like 9600, 19200, 38400, 57600, 115200 and so on you have to use a special frequency for MCU clock, like 7.3728 MHz.

Regards,

- mike