PIC18F4520 single chip ultrasonic distance measurement main part program-EEWORLD

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Test environment: MPLAB IDE v8.73a

Microcontroller model: PIC18F4520
Required devices: Ultrasonic module
The circuit connection diagram is as follows: Ultrasonic ranging subfunction:

unsigned int chaosheng()
{
unsigned int temp1, temp2; //Define two unsigned integer variables to store distance values

INPUT = 1;
delay(50); //delay
INPUT = 0;

while(!OUTPUT); //When the ultrasonic output pin outputs a high level, turn on timer 0 and start timing
TMR1ON = 1;
while(OUTPUT); //When the ultrasonic output pin outputs a low level, turn off timer 0 and stop timing
TMR1ON = 0;

//Calculate the distance measured by ultrasound
temp1 = TMR1L; //Assign the lower 8 bits of TMR1 to the temp1 variable
temp2 = TMR1H; //Assign the upper 8 bits of TMR1 to the temp2 variable
temp2 = (temp2 << 8) + temp1; //Shift temp2 left by 8 bits and add temp1

TMR1H = 0; //The high 8 bits of TMR1 are cleared to prepare for the next distance measurement
TMR1L = 0; //The low 8 bits of TMR1 are cleared to prepare for the next distance measurement

//Distance = time/2 * speed
//Distance: distance; time: temp2/2 in μs; speed: 340m/s
//Pay attention to the units here, and need to convert them so that the final distance unit is cm/s
distance = temp2 * 1.7/100; //There is a certain error, which can be filled by software. According to the actual measured value, add or subtract an error value to the expression on the right.

return distance; //Return the distance value measured by ultrasound. Here, distance is a global variable and can be used in other programs, such as the LCD display part, which can be passed as an actual parameter to its corresponding program for display.

}

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