基于atmega88的超声波测距仪

1、基于atmega88的超声波测距仪作品采用ATMEL公司的ATMGEA88 作为MCU，内部有8K FLASH，1kram。工作在内部8M RC振荡下，耗电仅为2MA左右。采用RISC指令集的AVR核心，运算速度大大超过传统的51单片机。内部带有3个定时器，8路10位AD（模数转换器）,串口，硬件SPI，方便使用。大批量采购价格目前由于炒货的原因涨价到12RMB。（具体问题可以搜索下，网上吹捧得很多）推荐你看一下中文的PDF，到处都有下载的。采用这块芯片主要来说就有一点，比51先进，功耗低，内带AD，而且外部不需要加晶振。使用一块LCD5110手机屏作为显示设备，可以显示输出电压以及当前状态。

2、液晶屏参数为72*48，点阵式，使用一个驱动库作为支持，方便开发，工作在3.3V电压下。耗电极低，小于1MA，背光耗电为20MA。屏的资料到使用一片LDO（低压差线性稳压源）作为系统电源，LM1117-3.3V，输出电压为3.3V，最大电流500MA以下为单片机的复位电路和烧录程序用的接口本设计中应用了MAX232来放大发射的40K信号，MAX232本来是用作串口电源转换器，它的本质是一个电荷泵升压器，所以可以直接将发射电压提高到正负9伏，使信号发射能力大大加强。超声波发射头使用的是普通的压电式头，中心频率都在40KHZ。有R,T之分。由于接受到的信号比较小，所以使用运放将接收后的信号放大。A

3、D623为ADI公司的轨至轨仪表放大器，单电源优化，可以工作在3V的极低电压。只需要使用一个电阻就可以改变放大倍率，最大放大倍率为1000，带宽增益乘积比为1M。功耗极低，可以满足长期工作的需要。信号放大后，将输入到单片机的模拟比较器中进行比较。当信号输入幅度大于一定值时，定义为接受到信号。超声波发射后，等待第一次回波经过后，打开中断，就可以等待超声波信号的到来。只要将发射时间和接收时间用定时器计时，就可以精确的得出超声波回声所用的时间。然后通过18B20采集温度后便可以计算出当前测距仪与被测物体的距离经过测算后，我选择将AIN1的值确定为2.7V，这样在接收的回波中，可以通过延时去掉。具体可

4、以看波形。如图中所示，第一个黑点是我们发出的信号的时候，直接从发射头横向送到接收头造成的误差信号。第二个黑店是接收信号的回波。当我将触发点选择到2.7V时，延时0.5MS后，就可以将发射的第一个误差信号消去，并将中断打开，等待第二个信号的进入。当信号电平高于2.7V后（这个是一个正弦波，会上下波动的），模拟比较器将触发，并通过AVR内部的选通，进入定时器1的输入捕捉中断中。只要此时停下计时器，便可以得出信号发射到信号接收的时间差。造成这种状况的主要原因为PWM发射和关断有延时，而发射头本身的电容会导致发射继续持续一段时间软件流程图#include <mega88p.h>#inclu

5、de <delay.h>#include "lcd5110.h"unsigned int time,t;unsigned long int juli,c;unsigned char chufa,run,time0,time1,yichu,chaoshi;#define uint unsigned int#define uchar unsigned char/ Pin change 8-14 interrupt service routine#ifndef RXB8#define RXB8 1#endif#ifndef TXB8#define TXB8 0#end

6、if#ifndef UPE#define UPE 2#endif#ifndef DOR#define DOR 3#endif#ifndef FE#define FE 4#endif#ifndef UDRE#define UDRE 5#endif#ifndef RXC#define RXC 7#endif#define FRAMING_ERROR (1<<FE)#define PARITY_ERROR (1<<UPE)#define DATA_OVERRUN (1<<DOR)#define DATA_REGISTER_EMPTY (1<<UDRE)

7、#define RX_COMPLETE (1<<RXC)/ USART Receiver buffer#define RX_BUFFER_SIZE0 8char rx_buffer0RX_BUFFER_SIZE0;#if RX_BUFFER_SIZE0<256unsigned char rx_wr_index0,rx_rd_index0,rx_counter0;#elseunsigned int rx_wr_index0,rx_rd_index0,rx_counter0;#endif/ This flag is set on USART Receiver buffer ove

8、rflowbit rx_buffer_overflow0;/ USART Receiver interrupt service routineinterrupt USART_RXC void usart_rx_isr(void)char status,data;status=UCSR0A;data=UDR0;if (status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN)=0) rx_buffer0rx_wr_index0=data; if (+rx_wr_index0 = RX_BUFFER_SIZE0) rx_wr_index0=

9、0; if (+rx_counter0 = RX_BUFFER_SIZE0) rx_counter0=0; rx_buffer_overflow0=1; ; ;#ifndef _DEBUG_TERMINAL_IO_/ Get a character from the USART Receiver buffer#define _ALTERNATE_GETCHAR_#pragma used+char getchar(void)char data;while (rx_counter0=0);data=rx_buffer0rx_rd_index0;if (+rx_rd_index0 = RX_BUFF

10、ER_SIZE0) rx_rd_index0=0;#asm("cli")-rx_counter0;#asm("sei")return data;#pragma used-#endif/ Standard Input/Output functions#include <stdio.h>/ Timer 0 overflow interrupt service routineinterrupt TIM0_OVF void timer0_ovf_isr(void) #asm("cli")if(chaoshi=10) run=1;

11、chaoshi+; #asm("sei")/ Place your code hereuchar ds1820_reset(void) uchar i; DDRD.4=1; PORTD.4=0; delay_us(500); /*延时500uS(480-960)*/ PORTD.4=1; DDRD.4=0; delay_us(80); /*延时80uS*/ i =PIND.4; delay_us(500); /*延时500uS(保持>480uS)*/ if (i) return 0x00; else return 0x01; uchar ds1820_read_byt

12、e(void) uchar i; uchar value = 0; for (i = 8; i != 0; i-) value >>= 1; DDRD.4=1;PORTD.4=0;PORTD.4=1; DDRD.4=0; if (PIND.4) value|=0x80; delay_us(60); /*延时60uS*/ return(value); void ds1820_write_byte(uchar value) uchar i; for (i = 8; i != 0; i-) DDRD.4=1;PORTD.4=0; delay_us(4); if (value &

13、0x01) PORTD.4=1; delay_us(80); /*延时80uS*/ PORTD.4=1; /*位结束*/ value >>= 1; void ds1820_start(void) ds1820_reset(); ds1820_write_byte(0xCC); /*勿略地址*/ ds1820_write_byte(0x44); /*启动转换*/ unsigned int ds1820_read_temp(void) unsigned int i; uchar buf9; ds1820_reset(); ds1820_write_byte(0xCC); /*勿略地址*

14、/ ds1820_write_byte(0xBE); /*读取温度*/ for (i = 0; i < 9; i+) bufi = ds1820_read_byte(); i = buf1; i <<= 8; i |= buf0; i=i*0.625*100; return i; / Timer1 overflow interrupt service routineinterrupt TIM1_OVF void timer1_ovf_isr(void) #asm("cli") yichu+; #asm("sei") / Place yo

15、ur code here/ Timer1 input capture interrupt service routineinterrupt TIM1_CAPT void timer1_capt_isr(void) /定时器中断，处理停止计数器之后的工作 #asm("cli") TCCR1B=0x00; /停止计数器 time1=TCNT1L; time0=TCNT1H; time=time0*256+time1; ds1820_start(); delay_us(210); t=ds1820_read_temp(); /读取18b20的温度 LCD_write_6_8str

16、ing(0,0," Temperature "); LCD_write_6_8string(0,1," "); LCD_write_float(24,1,(float)t/1000); c=(unsigned long int)t*607/10000+33150; /计算声速 juli=(unsigned long int)time*c/80000/2; LCD_write_6_8string(0,2," Sound speed "); LCD_write_6_8string(0,3," cm "); LCD_wr

17、ite_float(12,3,(float)c/100); LCD_write_6_8string(0,4," Distance "); LCD_write_6_8string(0,5," cm "); LCD_write_float(12,5,(float)juli/100); /LCD_write_number(0,5,time); #asm("sei") / Place your code here / Declare your global variables herevoid main(void)/ Declare your

18、 local variables here/ Crystal Oscillator division factor: 1#pragma optsize-CLKPR=0x80;CLKPR=0x00;#ifdef _OPTIMIZE_SIZE_#pragma optsize+#endif/ Input/Output Ports initialization/ Port B initialization/ Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out / State7=0 State6=

19、0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0 PORTB=0x00;DDRB=0xFF;/ Port C initialization/ Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In / State6=T State5=T State4=T State3=P State2=P State1=T State0=T PORTC=0x0C;DDRC=0x00;/ Port D initialization/ Func7=In Func6=In Func5=

20、In Func4=In Func3=Out Func2=In Func1=In Func0=In / State7=T State6=T State5=T State4=T State3=0 State2=T State1=T State0=T PORTD=0x00;DDRD=0x08;/ Timer/Counter 0 initialization/ Clock source: System Clock/ Clock value: 7.813 kHz/ Mode: Normal top=FFh/ OC0A output: Disconnected/ OC0B output: Disconne

21、ctedTCCR0A=0x00;TCCR0B=0x05;TCNT0=0x00;OCR0A=0x00;OCR0B=0x00;/ Timer/Counter 1 initialization/ Clock source: System Clock/ Clock value: 8000.000 kHz/ Mode: Normal top=FFFFh/ OC1A output: Discon./ OC1B output: Discon./ Noise Canceler: Off/ Input Capture on Rising Edge/ Timer1 Overflow Interrupt: On/

22、Input Capture Interrupt: On/ Compare A Match Interrupt: Off/ Compare B Match Interrupt: OffTCCR1A=0x00;/TCCR1B=0x41;TCCR1B=0X00;TCNT1H=0x00;TCNT1L=0x00;ICR1H=0x00;ICR1L=0x00;OCR1AH=0x00;OCR1AL=0x00;OCR1BH=0x00;OCR1BL=0x00;/ Timer/Counter 2 initialization/ Clock source: System Clock/ Clock value: 800

23、0.000 kHz/ Mode: CTC top=OCR2A/ OC2A output: Disconnected/ OC2B output: Toggle on compare matchASSR=0x00;TCCR2A=0x12;TCCR2B=0x00;/TCCR2B=0x01;TCNT2=0x00;OCR2A=0x66;OCR2B=0x00;/*/ External Interrupt(s) initialization/ INT0: Off/ INT1: Off/ Interrupt on any change on pins PCINT0-7: Off/ Interrupt on a

24、ny change on pins PCINT8-14: On/ Interrupt on any change on pins PCINT16-23: OffEICRA=0x00;EIMSK=0x00;PCICR=0x02;PCMSK1=0x0C;PCIFR=0x02;*/ Timer/Counter 0 Interrupt(s) initializationTIMSK0=0x01;/ Timer/Counter 1 Interrupt(s) initializationTIMSK1=0x21;/ Timer/Counter 2 Interrupt(s) initializationTIMSK2=0x00;/ USART initialization/ Communication Parameters: 8 Data, 1 Stop, No Parity/ USART Receiver: On/ USART Transmitter: On/ USART0 Mode: Asyn