STM8--UART2

UART starts communication with a start bit, which is a low level output from the TX pin. Following the start bit is the 8-bit or 9-bit data to be sent. If there is a parity check, the data is followed by the parity check data information, and finally the stop bit, which can be set to 1, 2, or 1.5.

Sending configuration and single-byte communication process:

Register introduction:

Control Register 1 (UART_CR1):

 Control Register 2 (UART_CR2):

 Control Register 3 (UART_CR3):

 Baud Rate Register 1 (UART_BRR1):

 Baud Rate Register 2 (UART_B):

 Status Register (UART_SR):

 Data Register (UART_DR):

 manual:

1: Set data length, parity check, stop bit, interrupt usage, etc. The operation registers are CR1, CR2, CR3. The following is my serial port configuration code.

/*urat2 initialization*/

void uart2_init()

{

  UART2_CR1=0X14; //8 data, 1 parity check, 1 stop, enable receive interrupt

  UART2_CR2=0X2c;

  UART2_CR3=0X00;

  UART2_BRR2=0X03; //Baud rate configuration --9600

  UART2_BRR1=0X68;

}

2: Send data: The code is as follows. It is very simple. Just write data into the register.

        UART2_CR2&=0Xf7;

        UART2_DR=uart_put; //Serial port sends

        UART2_CR2|=0X08;

          while((UART2_SR&0X80)==0);//Wait for sending to complete

3: Receive output: I used the receive interrupt, so I received data in the interrupt processing function

#pragma vector=UART2_R_RXNE_vector

__interrupt void UART2_IRQHandler (void)

{

  while((UART2_SR&0X20)==0);//Wait for receiving to complete

      uart_get=UART2_DR; //Read the received value and clear the flag bit

}

Notice:

1: In STM8S, the M bit defines the frame length, not the length of the data bit! That is to say, the length located by the M bit is the sum of the number of "data bits + parity bits". When the data bit is 8 bits, when parity check is not used, the length of M is 8 bits; when parity check is used, the length of M should be 9 bits! Therefore, when writing a program, you cannot simply change the setting of the check bit;

2: Looking at the STM8S reference manual, we found that Bit0 in the status register UART_SR is PE, which indicates a parity error: PE=0, no parity error; PE=1, parity error. Under what circumstances is the PE flag cleared? We can see in the reference manual: To clear the PE flag, the software must follow the following sequence of operations: first read UART_SR, then read UART_DR. The program needs to detect PE and then determine whether to receive, because no matter what parity mode the sender uses or no parity, the microcontroller serial port will receive data. 

For example, I encountered such a problem during the sending process: 

Sender: 9600, N, 8, 1 (the number of data bits sent is 8) sends a byte 0xC5 1100 0101 

Recipient: 9600, O, 8, 1 

The receiver's PE bit is 0 and can be connected to 0xC5; at this time, the sender's stop bit is used as a check bit by the receiver. Since it is odd parity, and the check bit is 1 at this time, only data containing an even number of 1s can be received correctly.

3: When using the serial port debugging tool, please note that the parity bit of some serial port tools does not work. The parity bit of the sscom42 test can be used!