msp430g2xx2 usi 15

Master data should increment from 0x55 with each transmitted byte.

//****************************************************************************** // MSP430G2xx2 - I2C Slave Receiver / Slave Transmitter, multiple bytes

//

// Description: I2C Master communicates with I2C Slave using

// the USI Master data should increment from 0x55 with each transmitted byte // ACLK = n/a, MCLK = SMCLK = Calibrated 1MHz

//

// ***THIS IS THE SLAVE CODE***

//

// Slave Master

// (MSP430G2xx2_usi_12.c)

// MSP430G2xx2 MSP430G2xx2

//

-// /|\| /|\|

XIN|-// | | | | | |

// |RST |RST

XOUT|-// | | | |

// LED <-|P1.0 | | |

// | | | P1.0|-> LED

// | SDA/P1.7| ->|P1.6/SDA |

// | SCL/P1.6|< -|P1.7/SCL |

//

// Note: internal pull-ups are used in this example for SDA & SCL

//

// D Dang

// Texas Instruments Inc

// December 2010

// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10

//******************************************************************************

#include <msp430g2452.h>

#define Number_of_Bytes 5 // **** How many bytes?? ****

void Setup_USI_Slave(void);

char MST_Data = 0; // Variable for received data

char SLV_Data = 0x55;

char SLV_Addr = 0x90; // Address is 0x48<<1 for R/W

int I2C_State, Bytecount, transmit = 0; // State variables

void Data_RX(void);

void TX_Data(void);

void main(void)

{

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog

if (CALBC1_1MHZ ==0xFF || CALDCO_1MHZ == 0xFF) {

while(1); // If calibration constants erased // do not load, trap CPU!!

}

BCSCTL1 = CALBC1_1MHZ; // Set DCO

DCOCTL = CALDCO_1MHZ;

Setup_USI_Slave();

LPM0; // CPU off, await USI interrupt _NOP();

}

//****************************************************************************** // USI interrupt service routine

// Rx bytes from master: State 2->4->6->8

// Tx bytes to Master: State 2->4->10->12->14

//******************************************************************************

#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( even_in_range(I2C_State,14))

{

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 master read

SLV_Addr = 0x91; // Save R/W bit

transmit = 1;}

else{transmit = 0;

SLV_Addr = 0x90;}

USICTL0 |= USIOE; // SDA = output

if (USISRL == SLV_Addr) // Address match?

{

USISRL = 0x00; // Send Ack

P1OUT &= ~0x01; // LED off

if (transmit == 0){

I2C_State = 6;} // Go to next state: RX data

if (transmit == 1){

I2C_State = 10;} // Else go to next state: TX data }

else

{

USISRL = 0xFF; // Send NAck

P1OUT |= 0x01; // LED on: error

I2C_State = 8; // next state: prep for next Start }

USICNT |= 0x01; // Bit counter = 1, send (N)Ack bit break;

case 6: // Receive data byte

Data_RX();

break;

case 8:// Check Data & TX (N)Ack

USICTL0 |= USIOE; // SDA = output

if (Bytecount <= (Number_of_Bytes-2))

// If not last byte

{

USISRL = 0x00; // Send Ack

I2C_State = 6; // Rcv another byte

Bytecount++;

USICNT |= 0x01; // Bit counter = 1, send (N)Ack bit }

else // Last Byte

{

USISRL = 0xFF; // Send NAck

USICTL0 &= ~USIOE; // SDA = input

SLV_Addr = 0x90; // Reset slave address

I2C_State = 0; // Reset state machine

Bytecount =0; // Reset counter for next TX/RX }

break;

case 10: // Send Data byte

TX_Data();

break;

case 12:// Receive Data (N)Ack

USICTL0 &= ~USIOE; // SDA = input

USICNT |= 0x01; // Bit counter = 1, receive (N)Ack I2C_State = 14; // Go to next state: check (N)Ack break;

case 14:// Process Data Ack/NAck

if (USISRL & 0x01) // If Nack received

{

USICTL0 &= ~USIOE; // SDA = input

SLV_Addr = 0x90; // Reset slave address

I2C_State = 0; // Reset state machine

Bytecount = 0;

// LPM0_EXIT; // Exit active for next transfer }

else // Ack received

{

P1OUT &= ~0x01; // LED off

TX_Data(); // TX next byte

}

break;

}

USICTL1 &= ~USIIFG; // Clear pending flags

}

void Data_RX(void){

USICTL0 &= ~USIOE; // SDA = input

USICNT |= 0x08; // Bit counter = 8, RX data

I2C_State = 8; // next state: Test data and (N)Ack }

void TX_Data(void){

USICTL0 |= USIOE; // SDA = output

USISRL = SLV_Data++;

USICNT |= 0x08; // Bit counter = 8, TX data

I2C_State = 12; // Go to next state: receive (N)Ack }

void Setup_USI_Slave(void){

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

transmit = 0;

_EINT();

}