Problem in UART Library using P16F877A

int uart_rd;
int i=0;

void main() {
     ADCON1=0b111110;
     PORTC=0;
     PORTB=0;
     TRISB=0b000001;
     CMCON=7;
 
 UART1_Init(9600);               // Initialize UART module at 9600 bps
 Delay_ms(100);                  // Wait for UART module to stabilize



 while (1) {                    // Endless loop
    if (UART1_Data_Ready()){     // If data is received,
       uart_rd = UART1_Read();     // read the received data,
       if(uart_rd == 123){
        PORTB.RB1=1;
       }
       else if(uart_rd == 321){
        PORTB.RB1=0;
       }
    }
  }
}

 UART1_Read_Text(uart_rd,"s", 255);   // read input from uart

// ADC Variables
double temp_res;
const double res = 0.25;

// PID Variables
double Input, Output;
double errSum, lastErr;
double dErr,error;
unsigned long lastTime,now;
double timeChange;

// Clock Variable
int time;

// Position contral variables
double xPos,yPos,zPos;
double theta_1N,theta_2N,theta_3N;
double theta_1O,theta_2O,theta_3O;
double setPoint;
const int link_1 = 6;
const int link_2 = 4;
double d_1,DD;
double phi;

char uart_rd[7];
int Duty,x,y,_rd,flag;



// Resolution adjustment
double resAdjust(double theta_1N){

 setPoint=0;
 if(theta_1N < res){
   setPoint = res;
 }
 else{
  while(setPoint < theta_1N){
   setPoint+=res;
  }
 }
 return setPoint;
}

// Time function
void time() {

  if(INTCON.T0IF) { // TMR0 Overflow Interrupt Flag bit 1=> has overflowed &  0=> did not overflow
    time++ ; // Increase each 260us
    INTCON.T0IF = 0 ;
   }
}


// PID Computation Function
double Compute(double Input,double setPoint){

   /*How long since we last calculated*/
    now=time;
    timeChange = (now - lastTime);

   /*Compute all the working error variables*/
    error = setPoint - Input;
    errSum += (error * timeChange);
    dErr = (error - lastErr) / timeChange;

   /*Compute PID Output*/
     Output =  error +  errSum +  dErr;

   /*Remember some variables for next time*/
   lastErr = error;
   lastTime = time;
   return  error;
}

void serialPort(){
     
     for(x=0; x<7; x++){
     uart_rd[x] = '\0';      //  Initialize string with all '\0'
     }

   if (PIR1.RCIF) {    // test the interrupt for uart rx

     UART1_Read_Text(uart_rd,"s", 255);   // read input from uart
     
     PORTB.RB7=1; delay_ms(100);
     PORTB.RB7=0; delay_ms(100);
     
     flag = 1;
   }

   if(flag == 1){
      for(y=1; y<=atoi(uart_rd); y++){
       PORTB.RB3=1; delay_ms(100);
       PORTB.RB3=0; delay_ms(100);
      }
      flag = 0;
     }
          /*
     _rd = strcmp(uart_rd, "g");
     if(_rd == 0){
      Duty = 0;
      PWM1_Set_Duty(Duty);
     }
     */
 }


void main() {

     ADCON1=0b111110;
     PORTC=0;
     PORTB=0;
     TRISB=0b000001;
     CMCON=7;
     OPTION_REG.T0CS=0;
     INTCON.GIE = 1;
     INTCON.PEIE = 1;
     INTCON.TMR0IE = 1;
     PIE1.RCIE = 1; //enable interrupt.
     PWM1_Init(20000);
     PWM1_Start();
     Duty = 255;
     PWM1_Set_Duty(Duty);
     UART1_Init(9600);               // Initialize UART module at 9600 bps
     Delay_ms(100);                  // Wait for UART module to stabilize



 while(1){


      serialPort();
      time();
      theta_1N = 35;
      theta_1O = 100;
      setPoint = resAdjust(theta_1N);
      temp_res =  ADC_Read(0);
      temp_res *= 0.25;
      temp_res = Compute(temp_res,setPoint);

      // Motor Forward & Backward
      if(temp_res < 0.25){
       PORTB.RB5 = 0;
       PORTB.RB1 = 0;
      }
      else{
       if(theta_1N > theta_1O){
        PORTB.RB1 = PORTC.RC2;
        PORTB.RB5 = 0;
       }
       else{
        PORTB.RB5 = PORTC.RC2;
        PORTB.RB1 = 0;
       }
      }
     }
      theta_1O = theta_1N;
}