Posted on May 17, 2011 at 15:04I’ am having some problems with the UART Baudrate.
I using the STM8s208RB microcontroller.
I am cofiguring the UART3 with the STM libs that are provided by STMicroelectronics.
clock setting; ''high speed internal clock prescaler: 1''. (16MHz)
Baudrate_UART3 = 38400
when I check the serial communication an UART3 the baudrate of the send 10 bit messages are almost 10% off, 34598.
the send messages of the PC and chip that I want to communicate with have both a baudrate of 38450 ~ 38460.
in the AN2659 bootloader example code they rewrite BRR1 en BRR2 to set correct baudrate - bug in library.
void SetUARTSpeed(u16 AutobaudPulse)
{
u32 BaudRate;
//compute baudrate
AutobaudPulse += 20; //correct systematic error (experimental)
AutobaudPulse /= 7; //pulses ber one bit (sync byte has 7 ones)
BaudRate = CLK_GetClockFreq() / AutobaudPulse; //calculate baudrate
//set push-pull on UART_tx pin
GPIO_Init(UART1_TX_PORT, UART1_TX_PIN, GPIO_MODE_OUT_PP_HIGH_FAST);
//remove software pull-up on UART_rx pin
GPIO_Init(UART1_RX_PORT, UART1_RX_PIN, GPIO_MODE_IN_FL_NO_IT);
//init UART 8-bits, 1 stop bit, even parity
UART1_Cmd(ENABLE);
UART1_Init(BaudRate, UART1_WORDLENGTH_8D, UART1_STOPBITS_1, UART1_PARITY_NO, UART1_SYNCMODE_CLOCK_DISABLE, UART1_MODE_TXRX_ENABLE);
//to set correct baudrate - bug in library
UART1->BRR2 = (AutobaudPulse & 0x000F) | ((AutobaudPulse & 0xF000) >> 4);
UART1->BRR1 = (AutobaudPulse & 0x0FF0) >> 4;
}//SetUARTSpeed
//**************************************************************************
Is it correct that there is a bug in the UART libraries?
Is there a solution for it?
