基于atmega88的超聲波測(cè)距儀

1、基于atmega88的超聲波測(cè)距儀作品采用ATMEL公司的ATMGEA88 作為MCU，內(nèi)部有8K FLASH，1kram。工作在內(nèi)部8M RC振蕩下，耗電僅為2MA左右。采用RISC指令集的AVR核心，運(yùn)算速度大大超過(guò)傳統(tǒng)的51單片機(jī)。內(nèi)部帶有3個(gè)定時(shí)器，8路10位AD（模數(shù)轉(zhuǎn)換器）,串口，硬件SPI，方便使用。大批量采購(gòu)價(jià)格目前由于炒貨的原因漲價(jià)到12RMB。（具體問(wèn)題可以搜索下，網(wǎng)上吹捧得很多）推薦你看一下中文的PDF，到處都有下載的。采用這塊芯片主要來(lái)說(shuō)就有一點(diǎn)，比51先進(jìn)，功耗低，內(nèi)帶AD，而且外部不需要加晶振。使用一塊LCD5110手機(jī)屏作為顯示設(shè)備，可以顯示輸出電壓以及當(dāng)前狀態(tài)。

2、液晶屏參數(shù)為72*48，點(diǎn)陣式，使用一個(gè)驅(qū)動(dòng)庫(kù)作為支持，方便開(kāi)發(fā)，工作在3.3V電壓下。耗電極低，小于1MA，背光耗電為20MA。屏的資料到使用一片LDO（低壓差線性穩(wěn)壓源）作為系統(tǒng)電源，LM1117-3.3V，輸出電壓為3.3V，最大電流500MA以下為單片機(jī)的復(fù)位電路和燒錄程序用的接口本設(shè)計(jì)中應(yīng)用了MAX232來(lái)放大發(fā)射的40K信號(hào)，MAX232本來(lái)是用作串口電源轉(zhuǎn)換器，它的本質(zhì)是一個(gè)電荷泵升壓器，所以可以直接將發(fā)射電壓提高到正負(fù)9伏，使信號(hào)發(fā)射能力大大加強(qiáng)。超聲波發(fā)射頭使用的是普通的壓電式頭，中心頻率都在40KHZ。有R,T之分。由于接受到的信號(hào)比較小，所以使用運(yùn)放將接收后的信號(hào)放大。A

3、D623為ADI公司的軌至軌儀表放大器，單電源優(yōu)化，可以工作在3V的極低電壓。只需要使用一個(gè)電阻就可以改變放大倍率，最大放大倍率為1000，帶寬增益乘積比為1M。功耗極低，可以滿足長(zhǎng)期工作的需要。信號(hào)放大后，將輸入到單片機(jī)的模擬比較器中進(jìn)行比較。當(dāng)信號(hào)輸入幅度大于一定值時(shí)，定義為接受到信號(hào)。超聲波發(fā)射后，等待第一次回波經(jīng)過(guò)后，打開(kāi)中斷，就可以等待超聲波信號(hào)的到來(lái)。只要將發(fā)射時(shí)間和接收時(shí)間用定時(shí)器計(jì)時(shí)，就可以精確的得出超聲波回聲所用的時(shí)間。然后通過(guò)18B20采集溫度后便可以計(jì)算出當(dāng)前測(cè)距儀與被測(cè)物體的距離經(jīng)過(guò)測(cè)算后，我選擇將AIN1的值確定為2.7V，這樣在接收的回波中，可以通過(guò)延時(shí)去掉。具體可

4、以看波形。如圖中所示，第一個(gè)黑點(diǎn)是我們發(fā)出的信號(hào)的時(shí)候，直接從發(fā)射頭橫向送到接收頭造成的誤差信號(hào)。第二個(gè)黑店是接收信號(hào)的回波。當(dāng)我將觸發(fā)點(diǎn)選擇到2.7V時(shí)，延時(shí)0.5MS后，就可以將發(fā)射的第一個(gè)誤差信號(hào)消去，并將中斷打開(kāi)，等待第二個(gè)信號(hào)的進(jìn)入。當(dāng)信號(hào)電平高于2.7V后（這個(gè)是一個(gè)正弦波，會(huì)上下波動(dòng)的），模擬比較器將觸發(fā)，并通過(guò)AVR內(nèi)部的選通，進(jìn)入定時(shí)器1的輸入捕捉中斷中。只要此時(shí)停下計(jì)時(shí)器，便可以得出信號(hào)發(fā)射到信號(hào)接收的時(shí)間差。造成這種狀況的主要原因?yàn)镻WM發(fā)射和關(guān)斷有延時(shí)，而發(fā)射頭本身的電容會(huì)導(dǎo)致發(fā)射繼續(xù)持續(xù)一段時(shí)間軟件流程圖#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); /*延時(shí)500uS(480-960)*/ PORTD.4=1; DDRD.4=0; delay_us(80); /*延時(shí)80uS*/ i =PIND.4; delay_us(500); /*延時(shí)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); /*延時(shí)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); /*延時(shí)80uS*/ PORTD.4=1; /*位結(jié)束*/ value >>= 1; void ds1820_start(void) ds1820_reset(); ds1820_write_byte(0xCC); /*勿略地址*/ ds1820_write_byte(0x44); /*啟動(dòng)轉(zhuǎn)換*/ 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); /*讀取溫度*/ 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) /定時(shí)器中斷，處理停止計(jì)數(shù)器之后的工作 #asm("cli") TCCR1B=0x00; /停止計(jì)數(shù)器 time1=TCNT1L; time0=TCNT1H; time=time0*256+time1; ds1820_start(); delay_us(210); t=ds1820_read_temp(); /讀取18b20的溫度 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; /計(jì)算聲速 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