关于波特率的问题。有程序有现象，求解决。

只看该作者 · 2013-9-3 16:50

本帖最后由中国白杨于 2013-9-5 16:43 编辑

用的是MSP430F149这个芯片。利用usart时出现了这样一个现象：usart0在波特率2400,4800,9600,38400下都能实现收发，usart1在波特率2400,4800,9600,19200,下实现收发也没有问题，在38400波特率下发送也没有问题，就是在接收的时候接收不到，我测试了一下。串口发送FF,RXBUF1接收到FE,发送FE,RXBUF1接收到FC,发送FC,RXBUF1接收到F8，发送F8，RXBUF1接收到F0，发送F0，RXBUF1接收到E0，发送E0，接收C0，发送C0，接收80，发送80，接收00。发送EF,接收CE,发送CF,接收8E,发送8F,接收0E。7F及小于7F的接收不到。这个问题是怎么回事？

只看该作者 · 2013-9-3 17:09

哪位大侠给看看啊？咋没人呢？着急啊？

只看该作者 · 2013-9-3 17:10

只看该作者 · 2013-9-3 20:19

好贴顶一个~~顶顶

3万 · 2013-9-3 20:53

貌似接受的数据总是比发出来的小啊，好奇怪
能上传一下你的电路图和程序吗

只看该作者 · 2013-9-5 16:32

#include <msp430x14x.h>
#define MAX_RD_LEN    16
void Init_sys(void);
void Init_Uart(void);
unsigned char Receive[MAX_RD_LEN+3+1]={0};          //receive byte
unsigned int  Receive_Cnt=0;
unsigned char R_Time_cnt=0;
unsigned char R_Flag=0;
unsigned char R_End_Flag=0;             //If receive end flag equal 1,then receive end and storage message.
unsigned char Tmp_data_Len=0;
unsigned char *R_Data_Ptr=(unsigned char *)0x1000;//Storage message pointer;
//..........................................................................................................
void main(void)
{
  unsigned char i;
  Init_sys();
  Init_Uart();
  U0TCTL |=TXEPT;
  while(1)
  {
if(R_End_Flag==1)
   {
      if((Receive[0]==0xAA)&&(Receive[1]==0x00)&&(Receive[2]==0x00))
         {
         if(Receive_Cnt>MAX_RD_LEN+3) //if the length that program receive is longer than max receive data length,initialize the length.
            Receive_Cnt=MAX_RD_LEN+3;
         Tmp_data_Len=Receive_Cnt-3;
         WDTCTL=WDTPW+WDTHOLD;       //Disable WDT
         _DINT();                   //Disable interrupts
         while((BUSY&FCTL3)==1);    //Test BUSY  Loop while busy
         FCTL2=FWKEY+FSSEL1+FN0;    //SMCLK/2
         FCTL3=FWKEY;                //Clear LOCK
         FCTL1=FWKEY+ERASE;          //Enable erase
         *R_Data_Ptr=0;
         while((BUSY&FCTL3)==1);    //Test BUSY  Loop while busy
         FCTL1=FWKEY+WRT;          //Enable write and Disable erase
         *R_Data_Ptr++=Tmp_data_Len;  //First byte for storaging data length
         while((BUSY&FCTL3)==1);    //Test BUSY  Loop while busy
         for(i=3;i<Receive_Cnt;i++)
         {
         *R_Data_Ptr++=Receive[i];
            while((BUSY&FCTL3)==1);
         }
         FCTL3=FWKEY+LOCK;          //Done, set LOCK
         _EINT();                   //Enable interrupts
         R_Data_Ptr=(unsigned char *)0x1000;  //initialize pointer
         if(*R_Data_Ptr==Receive_Cnt-3)
         {
         //P5OUT|=RTS10;             //485处于发送状态
         TXBUF1=0xAA;
         while((U1TCTL&0x01)==0);
         TXBUF1=0x00;
         while((U1TCTL&0x01) ==0);
         TXBUF1=0x00;
         while((U1TCTL&0x01) ==0);
         //P5OUT&=~RTS10;             //485处于接收状态
         }
         }
      if((Receive[0]==0xAB)&&(Receive[1]==0x00)&&(Receive[2]==0x00))
         {
         //P5OUT|=RTS10;             //485处于发送状态
         TXBUF1=0xAB;
         while((U1TCTL&0x01)==0);
         TXBUF1=0x00;
         while((U1TCTL&0x01)==0);
         TXBUF1=0x00;
         while((U1TCTL&0x01)==0);
         if(*R_Data_Ptr==0xFF)
            {
            TXBUF1=0x00;
            while((U1TCTL&0x01) ==0);
            }
         else
            {
            Tmp_data_Len=*R_Data_Ptr++;
            for(i=0;i<Tmp_data_Len;i++)
               {
               TXBUF1=*R_Data_Ptr++;
               while((U1TCTL&0x01) ==0);
               }
            }
         //P5OUT&=~RTS10;             //485处于接收状态
         R_Data_Ptr=(unsigned char *)0x1000; //initialize pointer
         }
      Receive_Cnt=0;
      R_End_Flag=0;                //wait for next
   }
}
}
void Init_sys(void)             //Initalize MSP430 system
{
  unsigned char i;
//New:switch 7.3728MHZ and 32768HZ
WDTCTL=WDTPW+WDTHOLD;          //Stop WDT
BCSCTL1 &=~(XT2OFF+XTS);       //LFXT1 = LF XTAL and Put on XT2!
//BCSCTL1 |=DIVA_3;
do
{
IFG1 &=~OFIFG;                //Clear OSC fault flag
for (i=0xFF;i>0;i--);       // i = Delay*/
}
while((IFG1 & OFIFG)!=0);    //OSC fault flag set?
BCSCTL2 |=(SELM_2+SELS);
BCSCTL2 |=(DIVS0+DIVS1);       //;SMCKLK 分频8
//TIMERA 10ms
TACTL=TASSEL_2+MC0+TACLR;
CCTL0=CCIE;                   //捕获/比较寄存器CCR0
CCR0=9216-1;                   //CCR0  counts to 10ms;
return;
}
//......................................................................................................
void Init_Uart(void)
{
   UCTL1=CHAR+SWRST;             //8-bit characters(p216)
   UTCTL1=SSEL1;                //SMCLK;
   switch(3)
   {
   case 3:
         UBR01=0x18;             //38400;
         UBR11=0x00;
   }
   UMCTL1=0x00;                //7.3728MHz no modulation 115200
   UCTL1 &=~SWRST;
   ME2 |=(UTXE1+URXE1);       //Enable USART0 TXD/RXD
   IE2 |=URXIE1;                //Enable USART0 RX interrupt
   P3SEL |=0xC0;                //P3.6,7 = USART0 TXD/RXD
   P3DIR |=0x40;                //P3.6 = output direction
_EINT();
}
#pragma vector=TIMERA0_VECTOR    //在IAR2.0以上中断函数声明。
__interrupt void TIMERA0_rx (void)
{
   if(R_Flag==1)    //when R_Flag=1，receive time count add.
      {
      R_Time_cnt++;
      if(R_Time_cnt>=2)
      {
      R_End_Flag=1; //receive end and begin to handle in main
      R_Time_cnt=0; //intialize R_Time_cnt 0
      R_Flag=0;    //count stop
      }
      }
}
/*******************************************************************************/
//用来控制单片机与上位机之间的通信  232通信，注意：波特率38400行不通
/*******************************************************************************/
#pragma vector=UART1RX_VECTOR
__interrupt void usart1_rx (void)
  {
  Receive[Receive_Cnt]=RXBUF1;
  Receive_Cnt++;
  R_Flag=1;                   //begin to count
  R_Time_cnt=0;                //restart to count
  }

只看该作者 · 2013-9-5 16:43

现将程序上传如上，硬件电路时没有问题的。usart1
连接光耦，连接max202e，连接电脑。我再2400,4800,9600,19200下测试了，都能实现双向通讯，38400下可实现发送，但不能实现接收，接收出现的现象如我第一版所述。USART0和USART1还是有区别的是吗？在USART0下实现发送和接收知道115200还是很好的。这是怎么个情况，谁给解释一下呢？

关于波特率的问题。有程序有现象，求解决。

相关下载

相关帖子

技术新星奖章

晶莹之水滴

经常做客

永恒之光奖章

坚毅之洋流

十世金身

技术领袖奖章