Master data should increment from 0x55 with each transmitted byte.
Trang 1*******
// MSP430F20xx Demo - 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
// (msp430x20x3_usi_12.c)
// MSP430F20x2/3 MSP430F20x2/3
//
-// /|\| /|\|
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
//
// R B Elliott / H Grewal
// Texas Instruments Inc
// February 2008
// Built with IAR Embedded Workbench Version: 3.42A
//***********************************************************************
*******
#include <msp430x20x3.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!!
Trang 2}
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){
Trang 3I2C_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;
Trang 4case 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;
Trang 5_EINT(); }