#include <msp430g2231.h>         // It has the definitions for all the registers, modes, etc.
 
unsigned int temp;               // holds ADC result
char SLV_Data = 0;                     // Variable for transmitted data   
 
int main(void)
{
      WDTCTL = WDTPW + WDTHOLD;            // Stop watchdog
 
      ADC10CTL1 = INCH_10 + ADC10DIV_3;         // Select Channel 10 and clk divided by 4
      ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE;      // Set Reference value Enable interrupts and turns on the ADC10
      TACCR0 = 30;                              // Delay to allow Ref to settle. Definition in the user guide
      TACCTL0 |= CCIE;                          // Interrupt enable for the Capture Compare
      TACTL = TASSEL_2 | MC_1;                  // Source clock TACLK = SMCLK, Count mode :Up
 
      _EINT();                                  // General Interrupt Enable
 
while(1)
  {
     ADC10CTL0 |= ENC + ADC10SC;             // Sampling and conversion start
     temp = ADC10MEM - 50;
  }
}
 
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR (void)
{
        SLV_Data = temp-50;             // To the data readed from the ADC (range 0-1023) substract 50.
}
 
#pragma vector=TIMERA0_VECTOR
__interrupt void ta0_isr(void)
{
    ADC10CTL0 |= ENC;                     // Enable conversion
    TACTL = 0;                            // Clear the Timer A control register
}

#include <msp430g2231.h>
 
char SLV_Data = 0;                     // Variable for transmitted data
char SLV_Addr = 0x90;                  // Address is 0x48
int I2C_State = 0;                     // State variable
 
unsigned int temp;            // holds  ADC result
unsigned int IntDegC;
 
int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;            // Stop watchdog
  if (CALBC1_1MHZ==0xFF)               // If calibration constants erased
  {
    while(1);                          // do not load, trap CPU!!
  }
  DCOCTL = 0;                          // Select lowest DCOx and MODx settings
  BCSCTL1 = CALBC1_1MHZ;               // Set DCO
  DCOCTL = CALDCO_1MHZ;
 
  ADC10CTL1 = INCH_10 + ADC10DIV_3;         // Temp Sensor ADC10CLK/4
  ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE;      // Enable interrupts.
  TACCR0 = 30;                              // Delay to allow Ref to settle
  TACCTL0 |= CCIE;                          // Compare-mode interrupt.
  TACTL = TASSEL_2 | MC_1;                  // TACLK = SMCLK, Up mode.
 
  P1OUT = 0xC0;                        // P1.6 & P1.7 Pullups
  P1REN |= 0xC0;                       // P1.6 & P1.7 Pullups
  P1DIR = 0xFF;                        // Unused pins as outputs
  P2OUT = 0;
  P2DIR = 0xFF;
 
  USICTL0 = USIPE6+USIPE7+USISWRST;    // Port & USI mode setup
  USICTL1 = USII2C+USIIE+USISTTIE;     // Enable I2C mode & USI interrupts
  USICKCTL = USICKPL;                  // Setup clock polarity
  USICNT |= USIIFGCC;                  // Disable automatic clear control
  USICTL0 &= ~USISWRST;                // Enable USI
  USICTL1 &= ~USIIFG;                  // Clear pending flag
  _EINT();
 
  while(1)
  {
     ADC10CTL0 |= ENC + ADC10SC;             // Sampling and conversion start
     temp = ADC10MEM - 50;
 
  }
}
 
//******************************************************
// USI interrupt service routine
//******************************************************
#pragma vector = USI_VECTOR
__interrupt void USI_TXRX (void)
{
  if (USICTL1 & USISTTIFG)             // Start entry?
  {
    P1OUT |= 0x01;                     // LED on: Sequence start
    I2C_State = 2;                     // Enter 1st state on start
  }
 
  switch(I2C_State)
    {
      case 0: //Idle, should not get here
              break;
 
      case 2: //RX Address
              USICNT = (USICNT & 0xE0) + 0x08; // Bit counter = 8, RX Address
              USICTL1 &= ~USISTTIFG;   // Clear start flag
              I2C_State = 4;           // Go to next state: check address
              break;
 
      case 4: // Process Address and send (N)Ack
              if (USISRL & 0x01)       // If read...
                SLV_Addr++;            // Save R/W bit
              USICTL0 |= USIOE;        // SDA = output
              if (USISRL == SLV_Addr)  // Address match?
              {
                USISRL = 0x00;         // Send Ack
                P1OUT &= ~0x01;        // LED off
                I2C_State = 8;         // Go to next state: TX data
              }
              else
              {
                USISRL = 0xFF;         // Send NAck
                P1OUT |= 0x01;         // LED on: error
                I2C_State = 6;         // Go to next state: prep for next Start
              }
              USICNT |= 0x01;          // Bit counter = 1, send (N)Ack bit
              break;
 
      case 6: // Prep for Start condition
              USICTL0 &= ~USIOE;       // SDA = input
              SLV_Addr = 0x90;         // Reset slave address
              I2C_State = 0;           // Reset state machine
              break;
 
      case 8: // Send Data byte
              USICTL0 |= USIOE;        // SDA = output
              USISRL = SLV_Data;       // Send data byte
              USICNT |=  0x08;         // Bit counter = 8, TX data
              I2C_State = 10;          // Go to next state: receive (N)Ack
              break;
 
      case 10:// Receive Data (N)Ack
              USICTL0 &= ~USIOE;       // SDA = input
              USICNT |= 0x01;          // Bit counter = 1, receive (N)Ack
              I2C_State = 12;          // Go to next state: check (N)Ack
              break;
 
      case 12:// Process Data Ack/NAck
              if (USISRL & 0x01)       // If Nack received...
              {
                P1OUT |= 0x01;         // LED on: error
              }
              else                     // Ack received
              {
                P1OUT &= ~0x01;        // LED off
                SLV_Data++;            // Increment Slave data
              }
              // Prep for Start condition
              USICTL0 &= ~USIOE;       // SDA = input
              SLV_Addr = 0x90;         // Reset slave address
              I2C_State = 0;           // Reset state machine
              break;
    }
 
  USICTL1 &= ~USIIFG;                  // Clear pending flags
}
 
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR (void)
{
        SLV_Data = temp-50;
}
 
#pragma vector=TIMERA0_VECTOR
__interrupt void ta0_isr(void)
{
    ADC10CTL0 |= ENC;
    TACTL = 0;
}