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sudeep nandiki

by assigning the required DATA to USISRL register  will transmit the data from one launchpad to other or any PINs have to be used

Depending on the processor you have on the LaunchPad, different pins are used and in a different way. Some G2 processors have an USI module, some an USCI, and the two are completely different to handle.

However, an PSI communication needs an absolute minimum of 4 wires between the two peers: SOMI, SIMO, SCLK and GND. You may also add VCC if you want to power both from one supply, and a snychronisation signal that is controlled/checked by GPIO. Almost every commercial SPI slave requires such a signal, usually called chip select (CS).
And maybe an interrupt signal that tells teh SPI master that the SPi slave has something to tell.

Hi Jens-Michael Gross

       thank you very much , i used slave only in receiving mode and master only in transmitting mode. can you please check the code pasted below. please

master

#include <msp430g2231.h>
void main(void)
{
  volatile unsigned int i;

  WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer
  P1OUT =  0x10;                        // P1.4 set, else reset
  P1REN |= 0x10;                        // P1.4 pullup
  P1SEL |=0x06;
  //P1DIR = 0x01;                         // P1.0 output, else input
  USICTL0 |= USIPE7 +  USIPE6 + USIPE5 + USIMST + USIOE; // Port, SPI master
  USICTL1 |= USIIE;                     // Counter interrupt, flag remains set
  USICKCTL = USIDIV_4 + USISSEL_2;      // /16 SMCLK
  USICTL0 &= ~USISWRST;                 // USI released for operation
  USISRL = 0X02;                        // init-load data

  P1DIR |= 0x04;                        // Reset Slave
  P1DIR &= ~0x04;
  for (i = 0xFFF; i > 0; i--);          // Time for slave to ready
  USICNT = 8;                           // init-load counter

while (1)                                 // Loop
{
  unsigned i;
  for (i = 0xFFFF; i > 0; i--);           // Delay
  while (!(USIIFG & USICTL1));            // Counter clear?
  USISRL=0X02;

                   // Read data are ready to be written
  USICNT = 8;         // re-load counter
  for (i = 0xFFFF; i > 0; i--);

  USISRL=0X03;

  USICNT=8;
}
}

slave

#include <msp430g2231.h>


void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer
 // P1OUT =  0x10;                        // P1.4 set, else reset
 // P1REN |= 0x10;                        // P1.4 pullup
  //P1DIR = 0x01;                       // P1.0 output, else input
   // P1SEL |=0x0A;
  USICTL0 |= USIPE7  + USIPE5 + USIOE; // Port, SPI slave
  USICTL1 |= USIIE;                     // Counter interrupt, flag remains set
  USICTL0 &= ~USISWRST;                 // USI released for operation
  //USISRL = P1IN;                        // init-load data
  USICNT = 8;                           // init-load counter
  while (1)                                 // Loop
   {

      unsigned i,m;
     for (i = 0xFFFF; i > 0; i--);           // Delay
     while (!(USIIFG & USICTL1));            // Counter clear?
    m=USISRL;
     if( m== 0X02)
         P1OUT |=0x01;
         else
             P1OUT &=~0x01;
            USICNT = 8;                             // re-load counter
   }
}