ultrasonic range finder problem

[cheenu02]

Hi,
I am doing ultrasonic range finder project using pic18f4552.while reading the values through serial port I am getting some error values like this
272
272
272
272
10
272
10
272
272
10
I dont know why this 10 comes.My ultrasonic module is Ts601.I attached the data sheet of Ts1601.Please help me

 

[engshahrul]

Which platform you receive? Show on hyperterminal or VB?

 

[FvM]

while reading the values through serial port I am getting some error values like this

Your report is incomprehensible. According to the datasheet, the said ultrasonic module hasn't a serial output.

 

[cheenu02]

hi,
This is my program.I am using PICC(CCSC) compiler

#include<18f452.h>
#fuses HS,NOWDT,NOLVP,NOPROTECT
#use delay(clock=12000000)
#use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C7)

#define rs PIN_C0
#define rw PIN_C1
#define en PIN_C2

void signal()
{
	output_low(PIN_B0);
	delay_us(2);
	output_high(PIN_B0);
	delay_us(5);
	output_low(PIN_B0);
}

void lcd_command(int16 command)
{
   output_d(command);
   delay_ms(50);
   output_low(rs);
   output_low(rw);
   output_high(en);
   delay_cycles(1);
   output_low(en);
}

void lcd_data(int16 data)
{
   output_d(data);
   delay_ms(50);
   output_high(rs);
   output_low(rw);
   output_high(en);
   delay_cycles(1);
   output_low(en);
}

void hex2dec(float value)
{
	int16 x,f1,f2,d1,d2,d3,int_val;
	float float_val;
	float_val=value+0.2;
	int_val=(int16)value+1;

	lcd_command(0x80);
   	lcd_data('v');
   	lcd_data('=');
	
	/*****************************************
		 Integer value calculation
	*****************************************/
   	x=int_val/10;          //102       
   	//d4=value%10;         //3
   	d3=int_val%10;    //2
   	d2=x%10;        //0
   	d1=x/10;        //1 

	lcd_command(0x82);
   	lcd_data(d1+48);
   	lcd_data(d2+48);
	lcd_data(d3+48);

	lcd_command(0x85);	
	lcd_data('.');
	
	/*****************************************
		Float value calculation
	*****************************************/
	f1=(int16)(float_val*10)%10;
	f2=(int16)(float_val*100)%10;
   
   	lcd_command(0x86);
	lcd_data(f1+48);
	lcd_data(f2+48);

	lcd_command(0x88);
	lcd_data('c');
   	lcd_data('m');
   	//lcd_data(d3+48);
   	//lcd_data(d4+48);
}
int16 range()
{
	int16 count=0;
	int1 state;

	set_tris_b(0x00);		//make PIB_B0 output
    signal();				//Trigger Ultrasonic*/
		
	set_tris_b(0xff);		//make PIN_B0 input

	while(state==0)
	{
		delay_cycles(2);
		state=input_state(PIN_B0);
	}
	while(state==1)
	{
		count++;
		delay_cycles(2);
		state=input_state(PIN_B0);
		delay_cycles(2);
	}
	//if(count>10)
	{
		printf("count=%ld\r\n",count);
		return(count);
	}
}
void main()
{
	float distance, value;
	lcd_command(0x38);
	lcd_command(0x0c);
	lcd_command(0x01);
	lcd_command(0x06);
	while(1)
	{
		value=range();
		distance=(value/19.2); 
		if(distance>2.5)
			hex2dec(distance);
	}
}

 

[FvM]

Variable state isn't initialized in your code, in so far the result is unpredictable.

Apart from this obvious problem, there may be a problem of additional spikes not shown in datasheet waveform. You should preferably check the real waveform with an oscilloscope. Possibly you need to supplement addidtional timing conditions when a pulse edge will be accepted.

In the present code, you don't need a state variable. You can simply perform a while(1) loop and break it conditionally.