//******************************************************************************
//  MSP430F22x4 Demo - USCI_B0 I2C Master TX/RX multiple bytes from MSP430 Slave
//                     with a repeated start in between TX and RX operations.
//
//  Description: This demo connects two MSP430's via the I2C bus. The master
//  transmits to the slave, then a repeated start is generated followed by a 
//  receive operation. This is the master code. This code demonstrates how to 
//  implement an I2C repeated start with the USCI module using the USCI_B0 TX 
//  interrupt.
//  ACLK = n/a, MCLK = SMCLK = BRCLK = default DCO = ~1.2MHz
//
// ***to be used with msp430x22x4_uscib0_i2c_13.c***
//
//                                /|\  /|\
//               MSP430F24x      10k  10k     MSP430F22x4
//                   slave         |    |        master
//             -----------------   |    |  -----------------
//           -|XIN  P3.1/UCB0SDA|<-|---+->|P3.1/UCB0SDA  XIN|-
//            |                 |  |      |                 |
//           -|XOUT             |  |      |             XOUT|-
//            |     P3.2/UCB0SCL|<-+----->|P3.2/UCB0SCL     |
//            |                 |         |                 |
//
//  R. B. Elliott / H. Grewal
//  Texas Instruments Inc.
//  April 2008
//  Built with IAR Embedded Workbench Version: 3.42A
//******************************************************************************
#include "msp430x22x4.h"

#define NUM_BYTES_TX 3                         // How many bytes?
#define NUM_BYTES_RX 2

int RXByteCtr, RPT_Flag = 0;                // enables repeated start when 1
volatile unsigned char RxBuffer[128];       // Allocate 128 byte of RAM
unsigned char *PTxData;                     // Pointer to TX data
unsigned char *PRxData;                     // Pointer to RX data
unsigned char TXByteCtr, RX = 0;
unsigned char MSData = 0x55;

void Setup_TX(void);
void Setup_RX(void);
void Transmit(void);
void Receive(void);

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P3SEL |= 0x06;                            // Assign I2C pins to USCI_B0

  while(1){

  //Transmit process
  Setup_TX();
  RPT_Flag = 1;
  Transmit();
  while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent

  //Receive process
  Setup_RX();
  Receive();
  while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent
  }
}

//-------------------------------------------------------------------------------
// The USCI_B0 data ISR is used to move received data from the I2C slave
// to the MSP430 memory. It is structured such that it can be used to receive
// any 2+ number of bytes by pre-loading RXByteCtr with the byte count.
//-------------------------------------------------------------------------------
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  if(RX == 1){                              // Master Recieve?
  RXByteCtr--;                              // Decrement RX byte counter
  if (RXByteCtr)
  {
    *PRxData++ = UCB0RXBUF;                 // Move RX data to address PRxData
  }
  else
  {
    if(RPT_Flag == 0)
        UCB0CTL1 |= UCTXSTP;                // No Repeated Start: stop condition
      if(RPT_Flag == 1){                    // if Repeated Start: do nothing
        RPT_Flag = 0;
      }
    *PRxData = UCB0RXBUF;                   // Move final RX data to PRxData
    __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0
  }}

  else{                                     // Master Transmit
      if (TXByteCtr)                        // Check TX byte counter
  {
    UCB0TXBUF = MSData++;                   // Load TX buffer
    TXByteCtr--;                            // Decrement TX byte counter
  }
  else
  {
    if(RPT_Flag == 1){
    RPT_Flag = 0;
    PTxData = &MSData;                      // TX array start address
    TXByteCtr = NUM_BYTES_TX;                  // Load TX byte counter
    __bic_SR_register_on_exit(CPUOFF);
    }
    else{
    UCB0CTL1 |= UCTXSTP;                    // I2C stop condition
    IFG2 &= ~UCB0TXIFG;                     // Clear USCI_B0 TX int flag
    __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0
    }
  }
 }

}

void Setup_TX(void){
  _DINT();
  RX = 0;
  IE2 &= ~UCB0RXIE;
  while (UCB0CTL1 & UCTXSTP);               // Ensure stop condition got sent// Disable RX interrupt
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
  UCB0CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK, keep SW reset
  UCB0BR0 = 12;                             // fSCL = SMCLK/12 = ~100kHz
  UCB0BR1 = 0;
  UCB0I2CSA = 0x48;                         // Slave Address is 048h
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  IE2 |= UCB0TXIE;                          // Enable TX interrupt
}
void Setup_RX(void){
  _DINT();
  RX = 1;
  IE2 &= ~UCB0TXIE;
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
  UCB0CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK, keep SW reset
  UCB0BR0 = 12;                             // fSCL = SMCLK/12 = ~100kHz
  UCB0BR1 = 0;
  UCB0I2CSA = 0x48;                         // Slave Address is 048h
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  IE2 |= UCB0RXIE;                          // Enable RX interrupt
}
void Transmit(void){
    PTxData = &MSData;                      // TX array start address
    TXByteCtr = NUM_BYTES_TX;                  // Load TX byte counter
    while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent
    UCB0CTL1 |= UCTR + UCTXSTT;             // I2C TX, start condition
    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
}
void Receive(void){
    PRxData = (unsigned char *)RxBuffer;    // Start of RX buffer
    RXByteCtr = NUM_BYTES_RX-1;              // Load RX byte counter
    while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent
    UCB0CTL1 |= UCTXSTT;                    // I2C start condition
    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
}