Use 8051 and HC-SR04 to measure distance in the range of 1 to 8 inches.

1.35/100 = 1/x => 74.074 us for 1 inch one direction), so in both 2 direction it is 148.148 us and code need to modify is below, thank you..

Summary of the 8051 software you develop:

Configure timer peripherals

use 8051 to generate 10us TRIGGER pulse for HC-SR04

use 8051 to measure ECHO pulse from HC-SR04

convert ECHO pulse to distance in inches and display distance on P1 LEDs as a bar graph

Distance from the sensor in Inches will be displayed on the LED as a bar graph according to the table below

Distance D (inches)	LEDs 7-0 ( - is off, + is on )
less than 1	---- ----
1 to 2	---- ---+
2 to 3	---- --++
3 to 4	---- -+++
4 to 5	---- ++++
5 to 6	---+ ++++
6 to 7	--++ ++++
7 to 8	-+++ ++++
more than 8	++++ ++++

Your program should perform about 1 measurement per second

#define TH0_INITIAL_VALUE 0xFC

#define TL0_INITIAL_VALUE 0x68

#include

unsigned int msCount;

// timer should execute every ms when gate pin == 1

void timer0() interrupt 1{

msCount++;

TH0 = TH0_INITIAL_VALUE; // reload timer high 0

TL0 = TL0_INITIAL_VALUE; // reload timer low 0

//TF0 = 0; // clear timer flag - statement not needed

}

void timer0_Config1(){

// Configure timer 0 in mode 1 with GATE control

TMOD |= 0x09; // Tiemr0 Gate = 1 and {M1,M0} = 0b01

TH0 = TH0_INITIAL_VALUE;

TL0 = TL0_INITIAL_VALUE;

ET0 = 1; // Enable timer0 interrupts

TR0 = 1; // Start timer 0

EA = 1; // Enable All interrupts

}

void main( void ){

timer0_Config1();

P1 = 0; // initialize P1

while( 1 ){ // BEGIN super loop

msCount = 0; // initialize microsecond count

while( !INT0 ); // wait for port 3 pin 2 to go to logic 1

while( INT0 ); // wait while the external interrupt pin is high

P1 = msCount;

// while( P0 != 0xF0 ) ; // wait until unlock code is entered on P0

} // END of super loop

}

/*

CALCULATION

Machine Cycle Frequencey = Fc / 12

Machine Cycle Frequencey = 11.0592MHz / 12 = 921600Hz

Machine Cycle Frequency = 921.6kHz

Machine Cycle Time = 1/921600

Machine Cycle Time = 1.085us

timerTickTime = Machine Cycle Time

1ms count requires how many timeouts?

numTimerTicks = 1ms / 1.085us

numTimerTicks = 1000us / 1.085us

numTimerTicks = 921

{ TH0, TL0 } = -920 -> FC68

*/