My Program

Hello Everyone,
with the help of codes found in the net, I have written these codes for controlling pressure in a pneumatic system.The pressure sensor has the range 2.5-4.5 volts. The set point is 3.5 volts.
[CODE]
#include <stdio.h>

#include <reg167.h>


// **************** GLOBAL VARIABLES AND CONSTANTS **************************

// for sensors

int sensorValue ;


// for PID control

int output ;

float currentError=0;

float setPoint=512 ;

#define maxValue 1023

#define minValue 0



//ISR address

#define INT 0x3F


//**************** FUNCTION PROTOTYPES *************************


// General function

void Initialize(void);


// control function

void PID(float);


// A/D converter

void AToDInitialize(void);

unsigned int ReadSensor(unsigned int);



// Interrupt routine

void Interrupt(void);



// ********************* MAIN PROGRAM ******************************



void main(void)

{

// ALWAYS DO THIS FIRST!

Initialize();


while(1)

;

}


// *************************** FUNCTION DEFINITIONS *************************



// Function: Initialize

// Purpose: Avoid floating pins by setting all of them to GND.

// Input conditions: None

// Arguments: None

// Return value(s): None

// Destroys: ALL REGISTERS - DPx and Px!



void Initialize(void)

{


P3 |= 0x0400; //set port 3.10 output latch (TXD)
DP3 |= 0x0400; // configure port 3.10 for output


// Initialize Analog/Digital

AToDInitialize();


// GLOBALLY ENABLE INTERRUPTS

IEN = 1;


}



// Function: PID

// Purpose: controller for driving the actuator

// Input conditions: None

// Arguments: Kp, Kd, Ki

// Return value(s): None

// Destroys: None



void PID(float currentError)

{

static float oldError = 0 ;

static float integralError = 0;

int temp ;

static float Kp = 1.2;

static float Ki = 9.5;

static float Kd = 0.05;

// Accumulate error for integral control

integralError += currentError;


temp=(currentError) * Kp + (currentError - oldError)* Kd+Ki * integralError ;

// Sanity checks

if(output + temp > minValue)

output = minValue ;

else if(output + temp < maxValue)

output = maxValue;

else

output += temp ;

//P3.10=output;


// Update your error

oldError = currentError ;

}


/************* Sensor functions - AToD module *******************/

// Function: AToDInitialize

// Purpose: Initialize AToD converter module

// Input conditions: None

// Arguments: None

// Return values: None

// Destroys: ADCON



void AToDInitialize(void)

{

ADCON = 0x0000; // ADM = 0x00, fixed channel SINGLE conversion

}



// Function: ReadSensor

// Purpose: Reads a sensor value from the specified analog input port (Port P5_0 to P5_15).

// Input conditions: None

// Arguments: input analog port to be read (0 to 15)

// Return values: converted digital value

// Destroys: no registers are destroyed



unsigned int ReadSensor(unsigned int port_no)

{

ADCON = (ADCON & 0xFFF0) | port_no;

ADST = 1; // start conversion

while(ADBSY) // wait for conversion

;

ADCIR = 0; // stop it

return (ADDAT & 0x0FFF);

}



//************ INTERRUPT ROUTINE *******

void Interrupt(void) interrupt INT

{

sensorValue=ReadSensor(0);

currentError=setPoint-sensorValue;

PID(currentError) ;


}
[/CODE]
As you can see 'output' is the output of PID contrller. I have set 3.10 port as output. How can I associate it with the output from the PID function?
Thanks