How to Interface external circuits with MSP430

#include <msp430.h>

void setup_uart(void);
void caliberate_clock(void);
void setup_adc(void);

//Counter for 1 second delay
unsigned int counter = 15; 
unsigned int timer = 0;
unsigned int i;
unsigned int var;

int main(void)
{
	// Stop WDT
	WDTCTL = WDTPW + WDTHOLD;                 
	caliberate_clock();

	// Select lowest DCOx and MODx settings
	DCOCTL = 0;
	// Set DCO
	BCSCTL1 = CALBC1_1MHZ;                    
	DCOCTL = CALDCO_1MHZ;
	// Configure Timer
	// CCR0 interrupt enabled
	CCTL0 = CCIE;                             
	CCR0 = 30000;
	// CCR0 = 65535;

	// SMCLK, continuous mode
	TACTL = TASSEL_2 + MC_1;  
        
	setup_uart();
        
        P2SEL |= BIT3; //ADC Input pin P2.3
	setup_adc();
	
	// Enter LPM0 w/ interrupt
	_BIS_SR(LPM0_bits + GIE);                 
}

void setup_uart(void)
{
	// UART setup section
	// Refer data sheet, pg 43
	P1SEL = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
	P1SEL2 = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
	UCA0CTL1 |= UCSSEL_2; // SMCLK

	// 1MHz 9600 (N=BRCLK/baudrate)
	UCA0BR0 = 0x6D;  //refer user guide
	UCA0BR1 = 0; // 1MHz 9600
	UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
	UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
}

void caliberate_clock(void)
{
	// If calibration constant erased
	if (CALBC1_1MHZ==0xFF)    
	{
		while(1); // do not load, trap CPU
	}
}

void setup_adc(void)
{
	// ADC10 control register 1 - Select the in-built temperature sensor
	// ADC10 control register 0 - Select sample and hold time, turn on ADC10
	// Select reference (Vr+ and Vr-
	ADC10CTL1 = INCH_5 + ADC10DIV_3 ;
	ADC10CTL0 = SREF_0 + ADC10SHT_3 + ADC10ON + ADC10IE;
        ADC10AE0 |= BIT3;
}

// Timer A0 interrupt service routine
#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
	// Add Offset to CCR0 
	CCR0 += 30000;

	// Increase timer1 value 
	timer++; 
	if (timer >= counter) {
		// start the conversion using ADC10SC as source for SHI 

		ADC10CTL0 |= ENC ; 

		var = ADC10MEM;

		// Send data over UART
		UCA0TXBUF = var;

		for (i = 0; i < 50000; i++);

		timer = 0;
	}
}

//******************************************************************************
// Filename: lab-final.c
// Read analog voltage and display that value over UART
//
//******************************************************************************
#include <msp430.h>

void setup_uart(void);
void caliberate_clock(void);
void setup_adc(void);

//Counter for 1 second delay
unsigned int counter = 15; 
unsigned int timer = 0;
unsigned int i;
unsigned int var;

int main(void)
{
    // Stop WDT
    WDTCTL = WDTPW + WDTHOLD;                 
    caliberate_clock();

    // Select lowest DCOx and MODx settings
    DCOCTL = 0;
    // Set DCO
    BCSCTL1 = CALBC1_1MHZ;                    
    DCOCTL = CALDCO_1MHZ;
    // Configure Timer
    // CCR0 interrupt enabled
    CCTL0 = CCIE;                             
    CCR0 = 30000;

    // SMCLK, continuous mode
    TACTL = TASSEL_2 + MC_1;  
        
    setup_uart();
        
    //P2SEL |= BIT3; //ADC Input pin P2.3
    setup_adc();
    
    // Enter LPM0 w/ interrupt
    _BIS_SR(LPM0_bits + GIE);                 
}

void setup_uart(void)
{
    // UART setup section
    // Refer data sheet, pg 43
    P1SEL = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
    P1SEL2 = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
    UCA0CTL1 |= UCSSEL_2; // SMCLK

    // 1MHz 9600 (N=BRCLK/baudrate)
    UCA0BR0 = 0x6D;  //refer user guide
    UCA0BR1 = 0; // 1MHz 9600
    UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
    UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
}

void caliberate_clock(void)
{
    // If calibration constant erased
    if (CALBC1_1MHZ==0xFF)    
    {
        while(1); // do not load, trap CPU
    }
}

void setup_adc(void)
{
    // ADC10 control register 1
    // ADC10 clock source select; ADC10SSELx
    // Input Channel
    // ADC10 clock divider
    ADC10CTL1 = INCH_5 + ADC10DIV_3 | ADC10SSEL0|ADC10SSEL1;
    
    // ADC10 control register 0
    // Select Internal reference voltage(Vr+ = VCC and Vr- = VSS) using REFON
    // and SREF_0
    // Sample and hold time set to 64 × ADC10CLKs using ADC10SHT_3
    // Enable the ADC10 core using ADC10ON bit
    
    ADC10CTL0 = SREF_0 + ADC10SHT_3 +  REFON + ADC10ON;
    
    //BIS.B #08h,&ADC10AE0 ; P2.3 ADC10 function and enable
    // Input channel 5 INCH_5 was selected above
    // These bits enable the corresponding pin for analog input. BIT0 
    // corresponds to A0, BIT1 corresponds to A1, etc.
    ADC10AE0 |= BIT5;
}

// Timer A0 interrupt service routine
#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
    // Add Offset to CCR0 
    CCR0 += 30000;

    // Increase timer1 value 
    timer++; 
    if (timer >= counter) {
        
        // start the conversion using ADC10OSC as source of conversion clock 
        ADC10CTL0 |= ENC + ADC10SC; 

        var = ADC10MEM;

        // Send data over UART
        UCA0TXBUF = var;

        for (i = 0; i < 50000; i++);

        timer = 0;
    }
}

    P2SEL |= BIT3;
    ADC10CTL1 = INCH_3 + ADC10DIV_3 | ADC10SSEL0|ADC10SSEL1;
    ADC10AE0 |= BIT3;