1 #include "msp430g2553.h" 2 #include "stdio.h" 3 4 5 unsigned char RxFlag; 6 unsigned char Byte_H; 7 unsigned char Byte_L; 8 unsigned int Dist; 9 unsigned int DistData[8]; 10 unsigned int DistAverage; 11 12 13 int putchar(int ch) 14 { 15 while(!(IFG2&UCA0TXIFG)); 16 UCA0TXBUF=ch; 17 return ch; 18 } 19 20 21 void sendChar(unsigned char c) 22 { 23 while(!(IFG2&UCA0TXIFG)); 24 UCA0TXBUF=c; 25 } 26 27 void sendStr(unsigned char *s) 28 { 29 while(*s!='\0') 30 { 31 sendChar(*s); 32 s++; 33 } 34 } 35 36 void main(void) 37 38 { 39 40 unsigned char i; 41 42 WDTCTL = WDTPW + WDTHOLD; // Stop WDT 43 44 BCSCTL1 = CALBC1_1MHZ; // Set DCO 45 DCOCTL = CALDCO_1MHZ; 46 BCSCTL2 &= ~(DIVS_3); 47 48 49 P1SEL = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD 50 P1SEL2 = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD 51 52 UCA0CTL1 |= UCSSEL_2; // SMCLK 53 UCA0BR0 = 104; // 1MHz 9600 54 UCA0BR1 = 0; // 1MHz 9600 55 UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1 56 UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine** 57 58 IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt 59 60 61 RxFlag=0; 62 63 _EINT(); 64 65 66 printf("\n%s\n","========超声波模块测试========="); 67 68 //__bis_SR_register(LPM0_bits + GIE); // Enter LPM0, interrupts enabled 69 70 71 while(1) 72 { 73 for(i=0;i<8;i++) 74 { 75 sendChar(0x55); 76 __delay_cycles(1000); 77 DistData[i]=Dist; 78 } 79 for(i=0;i<8;i++) 80 81 DistAverage += DistData[i]; 82 DistAverage = DistAverage >> 3; 83 84 __delay_cycles(1200000); 85 if(RxFlag == 0) 86 87 printf("\n距离: %d mm\n\n",DistAverage); 88 89 } 90 91 92 } 93 94 // Echo back RXed character, confirm TX buffer is ready first 95 96 #pragma vector=USCIAB0RX_VECTOR 97 __interrupt void USCI0RX_ISR(void) 98 { 99 100 while (!(IFG2&UCA0TXIFG)); // USCI_A0 TX buffer ready? 101 102 if(RxFlag == 0) 103 { 104 Byte_H=UCA0RXBUF; 105 RxFlag=1; 106 } 107 else 108 { 109 Byte_L=UCA0RXBUF; 110 Dist=Byte_H*256+Byte_L; 111 RxFlag = 0; 112 } 113 } 114
超声波使用串口通讯，与PC串口通讯共用RXD，TXD引脚，MSP430每隔一段时间，向串口发送0x55，在PC机上显示字符‘U’，发送8次，取平均值，在PC机上会看到
UUUUUUUU
距离: 3170 mm
可以知道程序是正确的，下面的工作加入超声波的测温功能，或进一步使用电平触发测量，并加入低功耗