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我正在尝试使用 uart 连接到 STM8。STM 似乎可以正常传输数据，但它接收到的似乎大多是垃圾，并且通常似乎一次接收 2 个字节。这是代码：

#include "../stm8.h"


//
//  Setup the system clock to run at 16MHz using the internal oscillator.
//
void InitialiseSystemClock()
{
    CLK_ICKR = 0;                       //  Reset the Internal Clock Register.
    CLK_ICKR |= CLK_ICKR_HSIEN ;                 //  Enable the HSI.
    CLK_ECKR = 0;                       //  Disable the external clock.
    while ((CLK_ICKR & CLK_ICKR_HSIRDY) == 0);       //  Wait for the HSI to be ready for use.
    CLK_CKDIVR = 0;                     //  Ensure the clocks are running at full speed.
    CLK_PCKENR1 = 0xff;                 //  Enable all peripheral clocks.
    CLK_PCKENR2 = 0xff;                 //  Ditto.
    CLK_CCOR = 0;                       //  Turn off CCO.
    CLK_HSITRIMR = 0;                   //  Turn off any HSIU trimming.
    CLK_SWIMCCR = 0;                    //  Set SWIM to run at clock / 2.
    CLK_SWR = 0xe1;                     //  Use HSI as the clock source.
    CLK_SWCR = 0;                       //  Reset the clock switch control register.
    CLK_SWCR |= CLK_SWCR_SWEN;                  //  Enable switching.
    while ((CLK_SWCR & CLK_SWCR_SWBSY) != 0);        //  Pause while the clock switch is busy.
}


//
//  Setup the UART to run at 115200 baud, no parity, one stop bit, 8 data bits.
//
//  Important: This relies upon the system clock being set to run at 16 MHz.
//
void init_uart()
{
    //
    //  Clear the Idle Line Detected bit in the status register by a read
    //  to the UART1_SR register followed by a Read to the UART1_DR register.
    //
    //unsigned char tmp = UART1_SR;
    //tmp = UART1_DR;

    //UART1_SR = 0xC0; // mcarter set to default value

    //
    //  Reset the UART registers to the reset values.
    //
    UART1_CR1 = 0;
    UART1_CR2 = 0;
    UART1_CR4 = 0;
    UART1_CR3 = 0;
    UART1_CR5 = 0;
    UART1_GTR = 0;
    UART1_PSCR = 0;
    //
    //  Now setup the port to 115200,n,8,1.
    //

    // clear certain bits
    UART1_CR1 &= ~UART1_CR1_M ;        //  8 Data bits.
    UART1_CR1 &= ~UART1_CR1_PCEN;     //  Disable parity

    // stop bits
    UART1_CR3 &= 0b11001111; // unmask the stop bit to default (1 stop bit)
    //UART1_CR3 |= 0b00100000; // two stop bits
    //UART1_CR3 |= 0b00110000; // 1.5 stop bits
    //UART1_CR3 &= ~UART1_CR3_STOP;     //  1 stop bit.

#if 1 //115200 baud
    //UART1_BRR2 = 0x0a;      //  given in original example
    UART1_BRR2 = 0x0b;      //  Set the baud rate registers to 115200 baud
    UART1_BRR1 = 0x08;      //  based upon a 16 MHz system clock.
#else // 9600 baud, but seems to be worse than 115200
    UART1_BRR2 = 0x03;
    UART1_BRR1 = 0x69;
#endif

    //
    //  Disable the transmitter and receiver.
    //
    //UART1_CR2_TEN = 0;      //  Disable transmit.
    //UART1_CR2_REN = 0;      //  Disable receive.
    //
    //  Set the clock polarity, lock phase and last bit clock pulse.
    //
    UART1_CR3 |= UART1_CR3_CPOL;
    UART1_CR3 |= UART1_CR3_CPHA;
    //UART1_CR3 |= UART1_CR3_LBCL; // this seems to cause problems

    UART1_CR2 |= UART1_CR2_TEN; // enable transmit
    UART1_CR2 |= UART1_CR2_REN; // enable receive
    UART1_CR3 |= UART1_CR3_CLKEN; // unable uart clock
}


char uart_getc()
{
    while((UART1_SR & UART1_SR_RXNE)==0); //  Block until char rec'd
    //char c =  UART1_DR;
    //return c;
    return UART1_DR;
}

void uart_putc(char c)
{
    while((UART1_SR & UART1_SR_TXE)==0); //  Wait for transmission complete
    UART1_DR = c; //  transmit char
}

void UARTPrintf(char *message)
{
    char *ch = message;
    while (*ch)
        uart_putc(*ch++);
}

void main()
{
    disable_interrupts();
    InitialiseSystemClock();
    init_uart();
    enable_interrupts();
    UARTPrintf("Uart example: you type, I echo\n\r");
    while (1)
    {
        //continue;
        char c = uart_getc();
        uart_putc(c);
        //UARTPrintf("Hello from my microcontroller....\n\r");
        //for (long counter = 0; counter < 2500000; counter++);
    }
}

相关的声明标题是：

#define UART1_SR   *(uchar*)(0x5230)
#define UART1_DR   *(uchar*)(0x5231)
#define UART1_BRR1 *(uchar*)(0x5232)
#define UART1_BRR2 *(uchar*)(0x5233)
#define UART1_CR1  *(uchar*)(0x5234)
#define UART1_CR2  *(uchar*)(0x5235)
#define UART1_CR3  *(uchar*)(0x5236)
#define UART1_CR4  *(uchar*)(0x5237)
#define UART1_CR5  *(uchar*)(0x5238)
#define UART1_GTR  *(uchar*)(0x5239)
#define UART1_PSCR *(uchar*)(0x523A)


#define UART1_CR1_M (1<<4)
#define UART1_CR1_PCEN (1<<2)

#define UART1_CR2_TEN           (1<<3)
#define UART1_CR2_REN           (1<<2)

#define UART1_CR3_STOP 4
#define UART1_CR3_CPOL (1<<2)
#define UART1_CR3_CPHA (1<<1)
#define UART1_CR3_LBCL (1<<0)
#define UART1_CR3_CLKEN (1<<3)

#define UART1_SR_TXE            (1<<7)
#define UART1_SR_TC             (1<<6)
#define UART1_SR_RXNE           (1<<5)

我不太确定停止位，以及所有这些。这只是“常规”串行通信。

我发现如果我取消注释该行

//UART1_CR3 |= UART1_CR3_LBCL; // this seems to cause problems

然后 stm8 打印出连续的垃圾流。但是随着它被注释掉，单片机似乎正确地知道有一个传输。不过，它所看到的似乎没有任何模式。

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1 回答 1

0

唔。违规行似乎是

UART1_CR3 |= UART1_CR3_CLKEN;

它的目的似乎是“启用 SCLK 引脚”。我不太明白这里发生了什么，但根据引脚图，引脚 PD4 的用途之一是 UART1_CK。因此，您可以将 UART 时钟连接到 STM8 并启用它？如果没有连接时钟，则会导致问题。真的，这没有多大意义；我不知道 uart 可以有外部时钟。

无论如何，注释掉这条线似乎已经解决了问题。

于 2020-09-19T21:16:23.220 回答