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这篇文章主要介绍了使用UART与PC通信实现msp430g2553单片机超声波测距示例,需要的朋友可以参考下.

适用于msp430g2553单片机 使用到了hc-sr04超声测距模块，使用UART与PC通信。

代码如下:

#include

long current_time;//最近一次测得时间

/*MyPro*/

#define LED_1 BIT0

#define SW_2 BIT3

#define TA1_1 BIT2 //TA0.1 HC-SR04 Echo

#define TRIG BIT4 //HC-SR04 Trig

#define ACCU_GRD 7 //Accuracy Grade "xxx.x"+''

#define MIN_UNIT_TO1M 1000 //1 m to 1 mm

/*TIMER0*/

#define SOUR_CLK 1045000

#define DIV_CLK_1 1

#define SYS_CLK_SIG_1 SOUR_CLK/DIV_CLK_1

#define DISTANCE 45//dm

#define TIMER_RIG_MAX 0xffff

#define MAX_TIME_1 DISTANCE*2/34*SYS_CLK_SIG_1

#ifdef MAX_TIME_1

#define SYS_CLK SYS_CLK_SIG_1

#endif

#define UART_TXD BIT2

void init_timer1()

{

P2SEL |= TA1_1; //TA1.1 CCI1B be used

P2DIR &= ~TA1_1;

TA1CTL = MC_0 + TASSEL_2; //TimerA_0 stop mode,clock=1Mhz

TA1CCTL1 = CCIE + SCCI + CCIS_1 + SCS + CAP + CM_2; //TA0CC1 capture mode + down edge

}

/*UART*/

void init_uart() //USCI 初始化函数

{

UCA0CTL1 |= UCSWRST; //初始化串口寄存器

UCA0CTL1 |= UCSSEL_2; //选择子系统时钟 1.045MHz

UCA0BR0 = 0x6d; //波特率为9600

UCA0BR1 = 0x00;

P1SEL |= UART_TXD;

P1SEL2 |= UART_TXD;

P1DIR |= UART_TXD; //将P1.2设为第二功能

UCA0CTL1 &= ~UCSWRST; //初始化结束

}

long cal_distance() //通过测得时间计算距离

{

return (long)((340*(0.5000*current_time/SYS_CLK)*MIN_UNIT_TO1M));

}

void delay() //粗略延迟

{

unsigned char i,j;

for(i=124;i>0;i--)

for(j=8;j>0;j--);

}

static char * translater(long distance) //将测得的距离以字符串形式存储

{

static char trans[ACCU_GRD];

int i;

long f;

trans[0]=' ';

if(distance)

for(i=1,f=MIN_UNIT_TO1M;i

{

if(i==4)

{

trans[i] = '.';

continue;

}

trans[i] = '0'+ distance/f;

distance %= f;

f /= 10;

}

trans[ACCU_GRD-1] = '';

return trans;

}

void once_pro() //发一次超声波

{

if(TA1CCTL1 & COV)

TA1CCTL1 &= ~COV;

if(!(P1IN & BIT3))

{

TA1R = 0;

P1OUT |= TRIG; //Trig 10 us 高电平

_EINT();

TA1CTL |= MC_2; //continue mode

P1OUT &= ~TRIG;

P1OUT |= LED_1;

while(TA1CCTL1 & CCIFG); //等待 捕捉中断结束

}

else

{

P1OUT &= ~LED_1;

_DINT();

}

}

void uart_txstring(char *string) //UART_TX 发送一个串

{

int i=0;

while(string[i++])

{

switch (i) //过滤无效 '0'

{

case 1:if(string[i]=='0') continue;

case 2:if(string[i]=='0'&&string[i-1]=='0') continue;

}

UCA0TXBUF = string[i];

delay();

}

}

/*UART_ISR*/

#pragma vector = USCIAB0TX_VECTOR

__interrupt void usci_txdistance() //向 PC 发送 测得的距离

{

uart_txstring("nr");

uart_txstring(" Current ");

uart_txstring(" distance: ");

uart_txstring(translater(cal_distance()));

uart_txstring(" cm");

IE2 &= ~UCA0TXIE;

}

/*TIMER0_INT_ISR*/

#pragma vector = TIMER1_A1_VECTOR

__interrupt void capture()

{

current_time = TA1CCR1;

TA1CTL &= ~MC_2;

TA1CCTL1 &= ~CCIFG; //清CC1中断标志位

IE2 |= UCA0TXIE;

}

/*Main*/

void main()

{

WDTCTL = WDTPW + WDTHOLD; //关狗

DCOCTL = 0;

BCSCTL1 = CALBC1_1MHZ;

DCOCTL = CALDCO_1MHZ;

P1OUT = 0;

P2OUT = 0;

P1REN |= SW_2;

P2REN |= TA1_1;

P1OUT |= SW_2;

P1DIR &= ~SW_2;

P1DIR = TRIG + LED_1;

init_timer1();

init_uart();

while(1)

{

int c = 8;

while(c--)

delay();

if(TA1CCTL1 & CCIFG)

TA1CCTL1 &= ~CCIFG;

once_pro();

}

}

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