codice porte uart

qualcuno può spiegarmi il seguente codice per programmazione porta uart e come funziona?? ( lo ho messo anche in allegato)

grazie:

#include "msp430g2553.h"

//

---

// Hardware-related definitions
//

---

#define UART_TXD 0x02 // TXD on P1.1 (Timer0_A.OUT0)
#define UART_RXD 0x04 // RXD on P1.2 (Timer0_A.CCI1A)

//

---

// Conditions for 9600 Baud SW UART, SMCLK = 1MHz
//

---

#define UART_TBIT_DIV_2 (1000000 / (9600 * 2))
#define UART_TBIT (1000000 / 9600)

//

---

// Global variables used for full-duplex UART communication
//

---

unsigned int txData; // UART internal variable for TX
unsigned char rxBuffer; // Received UART character

//

---

// Function prototypes
//

---

void TimerA_UART_init(void);
void TimerA_UART_tx(unsigned char byte);
void TimerA_UART_print(char *string);

//

---

// main()
//

---

void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

DCOCTL = 0x00; // Set DCOCLK to 1MHz
BCSCTL1 = CALBC1_1MHZ;
DCOCTL = CALDCO_1MHZ;

P1OUT = 0x00; // Initialize all GPIO
P1SEL = UART_TXD + UART_RXD; // Timer function for TXD/RXD pins
P1DIR = 0xFF & ~UART_RXD; // Set all pins but RXD to output
P2OUT = 0x00;
P2SEL = 0x00;
P2DIR = 0xFF;

__enable_interrupt();

TimerA_UART_init(); // Start Timer_A UART
TimerA_UART_print("G2xx2 TimerA UART\r\n");
TimerA_UART_print("READY.\r\n");

for (;
{
// Wait for incoming character
__bis_SR_register(LPM0_bits);

// Update board outputs according to received byte
if (rxBuffer & 0x01) P1OUT |= 0x01; else P1OUT &= ~0x01; // P1.0
if (rxBuffer & 0x02) P1OUT |= 0x08; else P1OUT &= ~0x08; // P1.3
if (rxBuffer & 0x04) P1OUT |= 0x10; else P1OUT &= ~0x10; // P1.4
if (rxBuffer & 0x08) P1OUT |= 0x20; else P1OUT &= ~0x20; // P1.5
if (rxBuffer & 0x10) P1OUT |= 0x40; else P1OUT &= ~0x40; // P1.6
if (rxBuffer & 0x20) P1OUT |= 0x80; else P1OUT &= ~0x80; // P1.7
if (rxBuffer & 0x40) P2OUT |= 0x40; else P2OUT &= ~BIT2; // P2.2
if (rxBuffer & 0x80) P2OUT |= 0x80; else P2OUT &= ~BIT4; // P2.4

// Echo received character
TimerA_UART_tx(rxBuffer);
}
}
//

---

// Function configures Timer_A for full-duplex UART operation
//

---

void TimerA_UART_init(void)
{
TACCTL0 = OUT; // Set TXD Idle as Mark = '1'
TACCTL1 = SCS + CM1 + CAP + CCIE; // Sync, Neg Edge, Capture, Int
TACTL = TASSEL_2 + MC_2; // SMCLK, start in continuous mode
}
//

---

// Outputs one byte using the Timer_A UART
//

---

void TimerA_UART_tx(unsigned char byte)
{
while (TACCTL0 & CCIE); // Ensure last char got TX'd
TACCR0 = TAR; // Current state of TA counter
TACCR0 += UART_TBIT; // One bit time till first bit
TACCTL0 = OUTMOD0 + CCIE; // Set TXD on EQU0, Int
txData = byte; // Load global variable
txData |= 0x100; // Add mark stop bit to TXData
txData <<= 1; // Add space start bit
}

//

---

// Prints a string over using the Timer_A UART
//

---

void TimerA_UART_print(char *string)
{
while (*string) {
TimerA_UART_tx(*string++);
}
}
//

---

// Timer_A UART - Transmit Interrupt Handler
//

---

#pragma vector = TIMER0_A0_VECTOR
__interrupt void Timer_A0_ISR(void)
{
static unsigned char txBitCnt = 10;

TACCR0 += UART_TBIT; // Add Offset to CCRx
if (txBitCnt == 0) { // All bits TXed?
TACCTL0 &= ~CCIE; // All bits TXed, disable interrupt
txBitCnt = 10; // Re-load bit counter
}
else {
if (txData & 0x01) {
TACCTL0 &= ~OUTMOD2; // TX Mark '1'
}
else {
TACCTL0 |= OUTMOD2; // TX Space '0'
}
txData >>= 1;
txBitCnt--;
}
}
//

---

// Timer_A UART - Receive Interrupt Handler
//

---

#pragma vector = TIMER0_A1_VECTOR
__interrupt void Timer_A1_ISR(void)
{
static unsigned char rxBitCnt = 8;
static unsigned char rxData = 0;

switch (__even_in_range(TA0IV, TA0IV_TAIFG)) { // Use calculated branching
case TA0IV_TACCR1: // TACCR1 CCIFG - UART RX
TACCR1 += UART_TBIT; // Add Offset to CCRx
if (TACCTL1 & CAP) { // Capture mode = start bit edge
TACCTL1 &= ~CAP; // Switch capture to compare mode
TACCR1 += UART_TBIT_DIV_2; // Point CCRx to middle of D0
}
else {
rxData >>= 1;
if (TACCTL1 & SCCI) { // Get bit waiting in receive latch
rxData |= 0x80;
}
rxBitCnt--;
if (rxBitCnt == 0) { // All bits RXed?
rxBuffer = rxData; // Store in global variable
rxBitCnt = 8; // Re-load bit counter
TACCTL1 |= CAP; // Switch compare to capture mode
__bic_SR_register_on_exit(LPM0_bits); // Clear LPM0 bits from 0(SR)
}
}
break;
}
}



// Definizioni relative all'hardware
//

---

# define UART_TXD 0x02 / / TXD su P1.1 ( Timer0_A.OUT0 )
# define UART_RXD 0x04 / / RXD su P1.2 ( Timer0_A.CCI1A )

//

---

// Condizioni di 9600 Baud SW UART , SMCLK = 1MHz
//

---

# define UART_TBIT_DIV_2 ( 1000000 / ( 9600 * 2) )
# define UART_TBIT (1000000/9600)
//

---

// Variabili globali utilizzati per la comunicazione UART full-duplex
//

---

unsigned int txData ; / / UART variabile interna per TX
unsigned char rxBuffer ; / / carattere UART Ricevuto
//

---

// funzione prototipi
//

---

void TimerA_UART_init(void);
void TimerA_UART_tx(unsigned char byte);
void TimerA_UART_print(char *string);

//

---

// main ( )
//

---

void main ( void)
{
    WDTCTL = WDTPW + WDTHOLD ; // Stop watchdog timer

    DCOCTL = 0x00 ; / / Set DCOCLK a 1MHz
    BCSCTL1 = CALBC1_1MHZ ;
    DCOCTL = CALDCO_1MHZ ;

    P1OUT = 0x00 ; / / inizializzare tutte le GPIO
    P1SEL = UART_TXD + UART_RXD ; / funzione Timer per pin TXD / RXD
    P1DIR = 0xFF & ~UART_RXD ; / / Imposta tutti i pin , ma RXD all'uscita
    P2OUT = 0x00 ;
    P2SEL = 0x00 ;
    P2DIR = 0xFF ;

    __enable_interrupt () ;

    TimerA_UART_init ( ) ; / / Avvio Timer_A UART
    TimerA_UART_print ( " G2xx2 TimerA UART \r\ n" ) ;
    TimerA_UART_print ( " READY.\r\n" ) ;

    for (;
    {
        // Attesa per il personaggio in arrivo( INCOMING CARACTER)
        __bis_SR_register ( LPM0_bits );

        // Aggiorna Uscite in secondo byte ricevuto
   // Update board outputs according to received byte
if (rxBuffer & 0x01) P1OUT |= 0x01; else P1OUT &= ~0x01; // P1.0
if (rxBuffer & 0x02) P1OUT |= 0x08; else P1OUT &= ~0x08; // P1.3
if (rxBuffer & 0x04) P1OUT |= 0x10; else P1OUT &= ~0x10; // P1.4
if (rxBuffer & 0x08) P1OUT |= 0x20; else P1OUT &= ~0x20; // P1.5
if (rxBuffer & 0x10) P1OUT |= 0x40; else P1OUT &= ~0x40; // P1.6
if (rxBuffer & 0x20) P1OUT |= 0x80; else P1OUT &= ~0x80; // P1.7
if (rxBuffer & 0x40) P2OUT |= 0x40; else P2OUT &= ~BIT2; // P2.2
if (rxBuffer & 0x80) P2OUT |= 0x80; else P2OUT &= ~BIT4; // P2.4

        // Echo ricevuto il carattere
        TimerA_UART_tx ( rxBuffer ) ;
    }
}
/ /

---

---

/ / Funzione configura Timer_A per il funzionamento UART full-duplex
/ /

---

---

void TimerA_UART_init(void)
{
    TACCTL0 = OUT ; / / Set TXD Idle come Mark = '1 '
    TACCTL1 = SCS + CM1 + CAP + CCIE ; / / Sync, Neg Edge, Capture , Int
    TACTL = TASSEL_2 + MC_2 ; / / SMCLK , avviare in modalità continua
}
/ /

---

---

/ / Uscite di un byte usando l' UART Timer_A
/ /

---

---

vuoto TimerA_UART_tx ( byte unsigned char )
{
    while ( TACCTL0 & CCIE ) ; / / Assicurarsi ultimo carattere ottenuto TX'd
    TACCR0 = TAR ; / / Stato attuale del contatore TA
    TACCR0 += UART_TBIT ; / / Un po 'di tempo fino al primo bit
    TACCTL0 = OUTMOD0 + CCIE ; / / Set TXD su EQU0 , Int
    TxData = byte ; / / Carico variabile globale
    TxData |= 0x100 ; / / Aggiungere mark bit di stop per TxData
    TxData <<= 1; bit / / Aggiungere inizio space
}

/ /

---

---

/ / Stampa una stringa sopra utilizzando la UART Timer_A
/ /

---

---

TimerA_UART_print void ( char * string )
{
    while ( *string ) {
        TimerA_UART_tx ( *string++) ;
    }
}
/ /

---

---

/ / Timer_A UART - Transmit Interrupt Handler
/ /

---

---

#pragma vector = TIMER0_A0_VECTOR
__interrupt void Timer_A0_ISR(void)
{
    static unsigned char txBitCnt = 10;

    TACCR0 += UART_TBIT ; // Aggiungi Differenza CCRX
    if ( txBitCnt == 0 ) { // Tutti i bit TXed ?
        TACCTL0 & = ~CCIE ; // Tutti i bit TXed , disabilitare interrupt
        txBitCnt = 10; / / ricaricare contatore di bit
    }
    else {
        if ( txData & 0x01 ) {
          TACCTL0 & = ~OUTMOD2 ; // TX Mark '1 '
        }
        else {
          TACCTL0 |= OUTMOD2 ; // TX Spazio '0 '
        }
        txData >>= 1 ;
        txBitCnt--;
    }
}
/ /

---

---

/ / Timer_A UART - Receive Interrupt Handler
/ /

---

---

#pragma vector = TIMER0_A1_VECTOR
__interrupt void Timer_A1_ISR(void)
{
    static unsigned char rxBitCnt = 8;
    static unsigned char rxData = 0 ;

     switch (__even_in_range(TA0IV, TA0IV_TAIFG)) { // Use calculated branching
case TA0IV_TACCR1: // TACCR1 CCIFG - UART RX
TACCR1 += UART_TBIT; // Add Offset to CCRx
if (TACCTL1 & CAP) { // Capture mode = start bit edge
TACCTL1 &= ~CAP; // Switch capture to compare mode
TACCR1 += UART_TBIT_DIV_2; // Point CCRx to middle of D0
}
else {
rxData >>= 1;
if (TACCTL1 & SCCI) { // Get bit waiting in receive latch
rxData |= 0x80;
}
rxBitCnt--;
if (rxBitCnt == 0) { // All bits RXed?
rxBuffer = rxData; // Store in global variable
rxBitCnt = 8; // Re-load bit counter
TACCTL1 |= CAP; // Switch compare to capture mode
__bic_SR_register_on_exit(LPM0_bits); // Clear LPM0 bits from 0(SR)
}
}
break;
}
}

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