[资料分享] MSP432开发板串口调试

先将串口调试好，便于下一步工作的展开。首先，查看TI提供的代码例子，这个例子就在TI的MSPWare代码包内。注释如下：

 

//******************************************************************************

//  MSP432P401 Demo - eUSCI_A0 UART echo at 9600 baud using BRCLK = 12MHz

//

// Description: This demo echoes back characters received via a PC serialport.

//  SMCLK/DCO is used as a clock source and the device is put in LPM3

//  Theauto-clock enable feature is used by the eUSCI and SMCLK is turned off

//  when theUART is idle and turned on when a receive edge is detected.

//  Note thatlevel shifter hardware is needed to shift between RS232 and MSP

//  voltagelevels.

//

//  Theexample code shows proper initialization of registers

//  andinterrupts to receive and transmit data.

//  To testcode in LPM3, disconnect the debugger.

//

//

//

//               MSP432P401

//            -----------------

//        /|\|                 |

//          ||                 |

//         --|RST              |

//           |                 |

//           |                 |

//           |     P1.3/UCA0TXD|----> PC(echo)

//           |     P1.2/UCA0RXD|<---- PC

//           |                 |

//

//   Wei Zhao

//   TexasInstruments Inc.

//   October2015 (updated) | June 2014 (created)

//   Builtwith Code Composer Studio V6.0

//******************************************************************************

从以上信息我们可以看出，此段例程所要做的事情就是将板载串口配置成9600波特率工作的串口，并原样送回我们发送进去的数据。从示意图中我们可以看出，我们只需要一对收发线即可完成本实验。接下来分析其源代码。

#include "msp.h"

int main(void)

{

  WDTCTL =WDTPW | WDTHOLD;               // Stopwatchdog timer

 

  CS->KEY= 0x695A;                        //Unlock CS module for register access

  CS->CTL0= 0;                            // Resettuning parameters

  CS->CTL0= CS_CTL0_DCORSEL_3;                   //Set DCO to 12MHz (nominal, center of 8-16MHz range)

                                         //Select ACLK = REFO, SMCLK = MCLK = DCO

  CS->CTL1= CS_CTL1_SELA_2 | CS_CTL1_SELS_3 | CS_CTL1_SELM_3;

  CS->KEY= 0;                             // LockCS module from unintended accesses

 

  //Configure UART pins

  P1SEL0 |=BIT2 | BIT3;                  // set2-UART pin as second function

 

 __enable_interrupt();

 NVIC->ISER[0] = 1 << ((EUSCIA0_IRQn) & 31); // EnableeUSCIA0 interrupt in NVIC module

 

  //Configure UART

  UCA0CTLW0|= UCSWRST;

  UCA0CTLW0|= UCSSEL__SMCLK;             // PuteUSCI in reset

  // BaudRate calculation

  //12000000/(16*9600) = 78.125

  //Fractional portion = 0.125

  // User'sGuide Table 21-4: UCBRSx = 0x10

  // UCBRFx =int ( (78.125-78)*16) = 2

  UCA0BR0 =78;                           //12000000/16/9600

  UCA0BR1 =0x00;

  UCA0MCTLW= 0x1000 | UCOS16 | 0x0020;    //注意这一行的设定

 

  UCA0CTLW0&= ~UCSWRST;                  //Initialize eUSCI

  UCA0IE |=UCRXIE;                       // EnableUSCI_A0 RX interrupt

 

  __sleep();

 __no_operation();                      // For debugger

}

 

// UART interrupt service routine

void EUSCIA0_IRQHandler(void)

{

    if(UCA0IFG & UCRXIFG)

    {

     while(!(UCA0IFG&UCTXIFG));

     UCA0TXBUF = UCA0RXBUF;

     __no_operation();

    }

}

我们首先粗略地研究一下这段测试代码，忽略前半部分关于时钟设置的内容，检查我标记的注意行。UCA0MCTLW0寄存器的设定在芯片TechnicalReference Manual的745页，例程中基本是使用默认串口配置。串口通信波特率已经在前面代码中设定为9600。看明白了上述内容，就掌握了这块开发板串口的基本内容，有精力可以继续探索一下芯片手册，尝试串口的其他功能。重要提示，不要使用盗版ghost win7，这样会导致xds110板载调试器的驱动安装失败。