msp430g2xx2 usi 07

Master data is sent and increments from 0x00 with each transmitted // byte which is verified by the slave.. // LED off for address or data Ack; LED on for address or data NAck.

//****************************************************************************** // MSP430G2xx2 Demo - I2C Master Transmitter, single byte

//

// Description: I2C Master communicates with I2C Slave using

// the USI Master data is sent and increments from 0x00 with each transmitted // byte which is verified by the slave

// LED off for address or data Ack; LED on for address or data NAck

// ACLK = n/a, MCLK = SMCLK = Calibrated 1MHz

//

// ***THIS IS THE MASTER CODE***

//

// Slave Master

// (MSP430G2xx2_usi_08.c)

// MSP430G2xx2 MSP430G2xx2

//

-// /|\| /|\|

XIN|-// | | | | | |

// |RST |RST

XOUT|-// | | | |

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

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

// | SDA/P1.7|< -|P1.7/SDA |

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

char MST_Data = 0; // Variable for transmitted data

char SLV_Addr = 0x90; // Address is 0x48 << 1 bit + 0 for Write int I2C_State = 0; // State variable

void main(void)

{

volatile unsigned int i; // Use volatile to prevent removal

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;

P1OUT = 0xC0; // P1.6 & P1.7 Pullups, others to 0

P1REN |= 0xC0; // P1.6 & P1.7 Pullups

P1DIR = 0xFF; // Unused pins as outputs

P2OUT = 0;

P2DIR = 0xFF;

USICTL0 = USIPE6+USIPE7+USIMST+USISWRST; // Port & USI mode setup

USICTL1 = USII2C+USIIE; // Enable I2C mode & USI interrupt

USICKCTL = USIDIV_3+USISSEL_2+USICKPL; // Setup USI clocks: SCL = SMCLK/8 (~125kHz)

USICNT |= USIIFGCC; // Disable automatic clear control

USICTL0 &= ~USISWRST; // Enable USI

USICTL1 &= ~USIIFG; // Clear pending flag

_EINT();

while(1)

{

USICTL1 |= USIIFG; // Set flag and start communication LPM0; // CPU off, await USI interrupt

_NOP(); // Used for IAR

for (i = 0; i < 5000; i++); // Dummy delay between communication cycles

}

}

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

// USI interrupt service routine

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

#pragma vector = USI_VECTOR

interrupt void USI_TXRX (void)

{

switch(I2C_State)

{

case 0: // Generate Start Condition & send address to slave

P1OUT |= 0x01; // LED on: sequence start

USISRL = 0x00; // Generate Start Condition

USICTL0 |= USIGE+USIOE;

USICTL0 &= ~USIGE;

USISRL = SLV_Addr; // and transmit address, R/W = 0 USICNT = (USICNT & 0xE0) + 0x08; // Bit counter = 8, TX Address I2C_State = 2; // Go to next state: receive address (N)Ack

break;

case 2: // Receive Address Ack/Nack bit

USICTL0 &= ~USIOE; // SDA = input

USICNT |= 0x01; // Bit counter = 1, receive (N)Ack bit I2C_State = 4; // Go to next state: check (N)Ack

break;

case 4: // Process Address Ack/Nack & handle data TX

USICTL0 |= USIOE; // SDA = output

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

{ // Send stop

USISRL = 0x00;

USICNT |= 0x01; // Bit counter = 1, SCL high, SDA low I2C_State = 10; // Go to next state: generate Stop

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

}

else

{ // Ack received, TX data to slave

USISRL = MST_Data; // Load data byte

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

I2C_State = 6; // Go to next state: receive data (N)Ack P1OUT &= ~0x01; // Turn off LED

}

break;

case 6: // Receive Data Ack/Nack bit

USICTL0 &= ~USIOE; // SDA = input

USICNT |= 0x01; // Bit counter = 1, receive (N)Ack bit I2C_State = 8; // Go to next state: check (N)Ack

break;

case 8: // Process Data Ack/Nack & send Stop

USICTL0 |= USIOE;

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

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

else // Ack received

{

MST_Data++; // Increment Master data

P1OUT &= ~0x01; // Turn off LED

}

// Send stop

USISRL = 0x00;

USICNT |= 0x01; // Bit counter = 1, SCL high, SDA low I2C_State = 10; // Go to next state: generate Stop break;

case 10:// Generate Stop Condition

USISRL = 0x0FF; // USISRL = 1 to release SDA

USICTL0 |= USIGE; // Transparent latch enabled

USICTL0 &= ~(USIGE+USIOE);// Latch/SDA output disabled

I2C_State = 0; // Reset state machine for next transmission

LPM0_EXIT; // Exit active for next transfer break;

}

USICTL1 &= ~USIIFG; // Clear pending flag

}