Multiple Ultrasonic Distance Sensors on a Single PIC 18F4550.

PIC18F4550lib.c

#include "PIC18F4550lib.h"

void ___init_core___() {
        ADCON1 = 0x0F; // page 268, disable analaog
        CMCON = 0x07; // disable comparator
        INTCON2 = 0x80; // disable pull up in port b

        LATA = 0x00; // Make all output ports 0
        LATC = 0x00; // Make all output ports 0
        LATD = 0x00; // Make all output ports 0
        LATE = 0x00; // Make all output ports 0

        TRISA = 0x03; // Make 00000011 directional ports.
        TRISC = 0x00; // Make all ports output
        TRISD = 0x00; // Make all ports output
        TRISE = 0x00; // Make all ports output

        PORTA = 0x00; // Make all ports 0
        PORTC = 0x00; // Make all ports 0
        PORTD = 0x00; // Make all ports 0
        PORTE = 0x00; // Make all ports 0

        LATA = 0x03;
}

void main_init() {
     ___init_core___();
}

PIC18F4550lib.h

#ifndef ___PIC18F4550lib_H__
#define ___PIC18F4550lib_H__

void ___init_core___();
void main_init();

#endif

ping.c

#include "PIC18F4550lib.h"
unsigned long count_distance[3];
unsigned char finalcount[3];
double calculation[3];
char txt[15];
char msg[40];

void main() {
    ADCON1 |= 0x0F;
    CMCON  |= 7;
    main_init();
    
    TRISD = 0x2A;
    TRISB = 0x00;
    LATB = 0x00;
    LATD = 0;

    UART1_Init(9600);
    Delay_ms(100);

    while(1){
        count_distance[0] =0;
        count_distance[2] =0;
        count_distance[1] =0;
        
        LATD = 0x01;
        Delay_us(20);
        LATD = 0x00;
        while (PORTD.RD1 == 0)
        count_distance[0] = 0;
        while (PORTD.RD1 == 1)
        {
            count_distance[0]++;
        }
        if (count_distance[0] > 1000)
            count_distance[0] = 1000;

        calculation[0] = (255*count_distance[0]/1000);
        finalcount[0] = calculation[0];
        UART1_Write(finalcount[0]);
        ////////////////////////////////////////////////
        LATD = 0x04;
        Delay_us(20);
        LATD = 0x00;
        while (PORTD.RD3 == 0)
        count_distance[1] = 0;
        while (PORTD.RD3 == 1)
        {
            count_distance[1]++;
        }
        if (count_distance[1] > 1000)
            count_distance[1] = 1000;

        calculation[1] = (255*count_distance[1]/1000);
        finalcount[1] = calculation[1];
        UART1_Write(finalcount[1]);
        ////////////////////////////////////////////////
        LATD = 0x10;
        Delay_us(20);
        //Delay_ms(1000);
        LATD = 0x00;
        while (PORTD.RD5 == 0)
        count_distance[2] = 0;
        while (PORTD.RD5 == 1)
        {
            count_distance[2]++;
        }
        if (count_distance[2] > 1000)
            count_distance[2] = 1000;

        calculation[2] = (255*count_distance[2]/1000);
        finalcount[2] = calculation[2];
        UART1_Write(finalcount[2]);
        ////////////////////////////////////////////////

        UART1_Write(0);
        Delay_ms(1000);
        LATB = !PORTB;
    }
}

random.txt

rd0 output -> trigger
rd1 input -> echo
rd2 output -> led if (lessthan 3 inches)

trisd 
0000 1010
7654 3210
0010 0000
initial output
0000 0001

7654 3210
0000 0001
0010 1010
0000 0100
0001 0000

trisD
7654 3210
0010 1010
latc
0001 0000

serial.ino

char inputString[200] = "";         // a string to hold incoming data
boolean stringComplete = false;  // whether the string is complete

void setup() {
  // initialize serial:
  Serial.begin(9600);
  Serial1.begin(9600);
}

void loop() {
  // print the string when a newline arrives:
  while (Serial1.available() ) {
    
    stringComplete=true;
    
    Serial.println(Serial1.read(),DEC);
  }
}