MSP430G2553: Pulse Sensor ,I can not read the BPM(beat per minute ) value on the Lcd Display

#include <msp430g2553.h>
#include "lcdLib.h"
#include <stdint.h>
unsigned int ADC_Result = 0x0000;
void adc_init();
void i2s(int i,char *s);
char s[100];
unsigned int BPM=0;       // used to hold the pulse rate
unsigned int IBI = 600;    // holds the time between beats
volatile int Signal;       // holds the incoming raw data
unsigned int Noise =0;     // the expected time for the second after a pulse,The variable Noise will help avoid noise later.
unsigned long sampleCounter=0; //The sampleCounter variable is what we use to keep track of time
unsigned long lastBeatTime=0;   
unsigned int P =512; 
unsigned int T = 512; 
unsigned int thresh = 512;  // Threshold value for 10 bit adc
unsigned int amp = 100; 
unsigned int Pulse= 0;   // true when pulse wave is high, false when it's low

unsigned int secondBeat= 0;
unsigned int firstBeat= 1;
unsigned int rate[10];
void timer_init();
//void lcd (void);
volatile int QS=0;     //becomes true when Msp430 finds a beat.
volatile int runningTotal = 0;
void BPM_Hesapla(void);
int main(void) {

WDTCTL = WDTPW + WDTHOLD;
DCOCTL = CALDCO_1MHZ;
BCSCTL1 = CALBC1_1MHZ;


P1DIR = 0x40;
P1SEL = 0x01;

lcdInit();
adc_init();
timer_init();
__bis_SR_register(GIE);


while (1) {
lcdSetText("BPM: ", 0, 0); 
i2s(BPM,s);
lcdSetText(s, 0, 1); 


}
}
//adc configuration
void adc_init(){ 
ADC10CTL0 &= ~ENC;
ADC10CTL0 = SREF_0 + ADC10SHT_3 + ADC10ON + MSC;//ADC10IE;
ADC10CTL1 = INCH_0 + SHS_0 + ADC10SSEL_0 + ADC10DIV_0 + CONSEQ_0; 
ADC10AE0 = BIT0; 
}
//timer configuration
void timer_init(){
CCTL0 = CCIE;
CCR0 = 1000;
TACTL = TASSEL_2 + ID_0 + MC_1;
}

#pragma vector=TIMER0_A0_VECTOR

__interrupt void timer_interrupt(void){
ADC10CTL0 |= ENC + ADC10SC; 
while (ADC10CTL1 & ADC10BUSY);
Signal = ADC10MEM;    // adc değerini sinyale atadık
sampleCounter += 2;    // we increased our time variable by two
Noise = sampleCounter - lastBeatTime;   

/* This function is called every 2 milliseconds. First thing to do is to take an analog reading of the Pulse Sensor. 
Next, we increment the variable sampleCounter. The sampleCounter variable is what we use to keep track of time. 
The variable N will help avoid noise later.
Next, we keep track of the highest and lowest values of the PPG wave, to get an accurate measure of amplitude.   */

if(Signal < thresh && Noise > (IBI/5)*3)  //
{
if (Signal < T){
T = Signal;
} 
}
if(Signal > thresh && Signal > P){
P = Signal;
} 
/* Variable P and T hold peak and trough values, respectively. 
The thresh variable is initialized at 512 (middle of analog range) and changes during run time to track a point at 50% of amplitude as we will see later. 
There is a time period of 3/5 IBI that must pass before T gets updated as a way to avoid noise and false readings from the dicroic notch. 
Now, lets check and see if we have a pulse. */

if (Noise > 250){
if ( (Signal > thresh) && (Pulse == 0) && (Noise > ((IBI/5)*3) )){ 
Pulse = 1; 
P1OUT |= 0x40;
IBI = sampleCounter - lastBeatTime;
lastBeatTime = sampleCounter; 
/*
Before we even consider looking for a heart beat, a minimum amount of time has to pass.
 This helps avoid high frequency noise. 250 millisecond minimum N places an upper limit of 240 BPM. 
 If you expect to have a higher BPM, adjust this accordingly and see a doctor. 
 When the waveform rises past the thresh value, and 3/5 of the last IBI has passed, we have a pulse! Time to set the Pulse flag and turn on the pulsePin LED. 
 (note: if you want to do something else with pin 13, comment out this line, and the later one too). 
 Then we calculate the time since the last beat to get IBI, and update the lastBeatTime.

The next bit is used to make sure we begin with a realistic BPM value on startup.   
*/
if(secondBeat){ 
secondBeat = 0; 
for(int i=0; i<=9; i++){ 
rate[i] = IBI; 
}
} 
if(firstBeat){ 
firstBeat = 0; 
secondBeat = 1; 
return; 
}
/*
The boolean firstBeat is initialized as true and secondBeat is initialized as false on start up, so the very first time we find 
a beat and get this far in the ISR, we get kicked out by the return; in the firstBeat conditional. That will end up throwing the
 first IBI reading away, cause it's lousy. The second time through, we can trust (more or less) the IBI, and use it to seed the 
 rate[] array in order to start with a more accurate BPM. The BPM is derived from an average of the last 10 IBI values, hence the need to seed.
Lets calculate BPM!
*/



runningTotal = 0;
for(int i=0; i<=8; i++){
rate[i] = rate[i+1]; 
runningTotal += rate[i]; 
}
rate[9] = IBI; 
runningTotal += rate[9]; 
runningTotal /= 10; 
BPM = 60000/runningTotal;
QS = 1; 
}}
/*
First, we grab a large variable, runningTotal, to collect the IBIs, then the contents of rate[] are shifted over and added to runnungTotal.
 The oldest IBI (11 beats ago) falls out of position 0, and the fresh IBI gets put into position 9. Then it's a simple process to average 
 the array and calculate BPM. Last thing to do is to set the QS flag (short for Quantified Self, awesome kickstarter supporters!) so the 
 rest of the program knows we have found the beat. That's it for the things to do when we find the beat.

There's a couple of other loose ends that need tying off before we're done, like finding the not-beat.
*/

if (Signal < thresh && Pulse == 1){ 
P1OUT &= ~0x40;
Pulse = 0; 
amp = P - T; 
thresh = amp/2 + T; 
P = thresh; 
T = thresh;
}
/*Pulse was declared true during the upward rise in Pulse Sensor signal when we found the beat, above, 
so when the signal crosses thresh going down, we can figure that the pulse is over. A little housekeeping 
in clearing pulsePin and the Pulse boolean. Then the amplitude of the wave that just passed is measured,
 and thresh is updated with the new 50% mark. P and T are reset to the new thresh. The algorithm is now primed and ready to find the next beat.

There's one more question to ask before the ISR is done. What if there are no beats?*/
if (Noise > 2500){ 
thresh = 512; 
P = 512; 
T = 512; 
firstBeat = 1; 
secondBeat = 0;
lastBeatTime = sampleCounter;
}
/*If there is no beat event for 2.5 seconds, variables used to find the heartbeat are 
reinitialized to the start up values. Sort of a soft soft-reset. That's the end of the ISR!*/

}

void i2s(int i,char *s) // Convert Integer to String
{char sign;short len;char *p;
sign='+';len=0;p=s;
if(i<0){sign='-';i=-i;}
do{*s=(i%10)+'0';s++;len++;i/=10;}while(i!=0);
if(sign=='-'){*s='-';s++;len++;}
for(i=0;i<len/2;i++){p[len]=p[i];p[i]=p[len-1-i];p[len-1-i]=p[len];}
p[len]=0;
}