Convert analogue voltage to distance value(GP2D12 sensor)??

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hweontey

Joined: 10 Mar 2008
Posts: 8

09 Jun 2008 19:42 Convert analogue voltage to distance value(GP2D12 sensor)??

I am new beginner in PIC microcontroller. I use PIC16F877A and Hi-Tech PICC LITE Compiler (C compiler). I already wrote C codes to get analogue voltage from GP2D12 distance sensor. But, i tried many times to convert it into distance value based on datasheet. I still can't get it. I NEED some help. I hope everyone can share experience and idea with me. The C codes as shown below. Thanks.

Added after 3 minutes:

My C codes:

//==================inckude=================================
#include<pic.h>

//===============configuration==============================
__CONFIG (0x3F32);

//===============define IO port=============================
#define lcd PORTB
#define RS RA2
#define E RA5
#define CHANNEL0 0b10000001 // AN0 sensor0

//==============FUNCTION PTOTOTYPE=========================
void e_pulse(void);//
void delay(unsigned short i);//
void send_char(unsigned char data);//
void send_config(unsigned char data);//
void lcd_goto(unsigned char data);//
void lcd_clr(void);//

void dis_num(unsigned long data);
void read_adc(void);
unsigned short read_temp(void);

//====================MAIN================================
unsigned short result;
unsigned short temp;

void main(void)
{
ADRESH=0; //clear A/D result
ADRESL=0; //clear A/D result

//setting ADCON1 Register
ADCON1=0b11000101; // A/D result right justified,
// configure RA2 and RA5 as digital I/O

TRISA=0b11011011; //configure PORTA I/O direction
TRISB=0b00000000; //configure PORTB as output
TRISC=0b00000000; //configure PORTC as output

PORTA=0;
PORTC=0;

while(1)
{
send_config(0b00000001); //clear display at lcd
send_config(0b00000010); //Lcd Return to home
send_config(0b00000110); //entry mode-cursor increase 1
send_config(0b00001100); //diplay on, cursor off and cursor blink off
send_config(0b00111000); //function set

lcd_goto(0); //cursor start from beginning

send_char('D');
send_char('I');
send_char('S');
send_char('T');
send_char('A');
send_char('N');
send_char('C');
send_char('E');
send_char('=');

while(1) //infinity loop
{

//sensor A
ADCON0=CHANNEL0; //CHANNEL0=0b10000001
lcd_goto(9);

read_adc();

temp=read_temp();//***Question: How to convert analogue voltage from sensor to distance in cm based on GP2D12 sensor??
dis_num(temp/10);
send_char('.');
dis_num(temp%10);
send_char('C');
send_char('M');

delay(2000);

}

}

}

//==================subroutine LCD setting ==========================

void send_config(unsigned char data)
{
RS=0;
lcd=data;
delay(500);
e_pulse();
}

void e_pulse(void)
{
E=1;
delay(500);
E=0;
delay(500);
}

void send_char(unsigned char data)
{
RS=1;
lcd=data;
delay(500);
e_pulse();
}

void lcd_goto(unsigned char data)
{
if(data<16)
{
send_config(0x80+data);
}
else
{
data=data-20;
send_config(0xc0+data);
}
}

void lcd_clr(void)
{
RS=0;
send_config(0x01);
delay(600);
}

void dis_num(unsigned long data)
{
unsigned char hundred_thousand;
unsigned char ten_thousand;
unsigned char thousand;
unsigned char hundred;
unsigned char tenth;

hundred_thousand = data/100000;
data = data % 100000;
ten_thousand = data/10000;
data = data % 10000;
thousand = data / 1000;
data = data % 1000;
hundred = data / 100;
data = data % 100;
tenth = data / 10;
data = data % 10;

if(hundred_thousand>0)
{
send_char(hundred_thousand + 0x30); //0x30 added to become ASCII code
send_char(ten_thousand + 0x30);
send_char(thousand + 0x30);
send_char(hundred + 0x30);
send_char(tenth + 0x30);
send_char(data + 0x30);
}

else if(ten_thousand>0)
{
send_char(ten_thousand + 0x30); //0x30 added to become ASCII code
send_char(thousand + 0x30);
send_char(hundred + 0x30);
send_char(tenth + 0x30);
send_char(data + 0x30);
}
else if(thousand>0)
{
send_char(thousand + 0x30); //0x30 added to become ASCII code
send_char(hundred + 0x30);
send_char(tenth + 0x30);
send_char(data + 0x30);
}
else if(hundred>0)
{
send_char(hundred + 0x30); //0x30 added to become ASCII code
send_char(tenth + 0x30);
send_char(data + 0x30);
}
else if(tenth>0)
{
send_char(tenth + 0x30); //0x30 added to become ASCII code
send_char(data + 0x30);
}
else send_char(data + 0x30); //0x30 added to become ASCII code
}

//==================subroutine ADC=========================

void read_adc(void)
{
unsigned short i;
unsigned long result_temp=0;
for(i=2000;i>0;i-=1) //looping 2000 times for getting average value
{
ADGO = 1; //ADGO is the bit 2 of the ADCON0 register
while(ADGO==1); //ADC start, ADGO=0 after finish ADC progress
result=ADRESH;
result=result<<8; //shift to left for 8 bit
result=result|ADRESL; //10 bit result from ADC

result_temp+=result;
}
result = result_temp/2000; //getting average value

}

unsigned short read_temp(void)
{
unsigned short temp;
temp=result;
return temp;
}

//==================subroutine DELAY==========================
void delay(unsigned short i)
{
for(;i>0;i--);
}

wizpic

Joined: 23 May 2004
Posts: 380
Helped: 26

09 Jun 2008 22:21 Re: Convert analogue voltage to distance value(GP2D12 sensor

I've add a quick look at the data sheet, I can see (I think) that it gives a 0-2.5V out

While I don't use C but the way I would go about doing it is set a distance and measure it with a ruler then see what what the ouput voltage would be at that distance then work out a routine by using floating point maths then set up the maximum distance then compare your reading's

Tell us some voltage reading your getting and I'll see if I can work it out in maths which you would have to convert it to C

wizpic

rikie_rizza

Joined: 05 Aug 2006
Posts: 334
Helped: 20
Location: Bikini Bottom, between a rock and a pineapple

10 Jun 2008 2:09 Convert analogue voltage to distance value(GP2D12 sensor)??

Do a calibration...never trust data sheet just like that.

DO A CALIBRATION FOR ANY INSTRUMENTATION DESIGN WORK!!!! NEVER TRUST DATA SHEET!!!

You know how to get data right? Do least square calculation...use MS Excel, is just that simple!