Question

Write programs for two MSP430 boards to do the following:

Board A: If the P1.1 button is pressed, send the message 0xAA via the UART at 9600 baud.
Board B: The red LED shall initially be off. However, if the Board B micro-controller receives a UART message of 0xAA at 9600 baud, turn on the Board B red LED.

Answer 1

Answer:

Explanation:

#include "msp430g2553.h"

#define TXLED BIT0

#define RXLED BIT6

#define TXD BIT2

#define RXD BIT1

const char string[] = { "Hello World\r\n" };

unsigned int i; //Counter

int main(void)

{

WDTCTL = WDTPW + WDTHOLD; // Stop WDT

DCOCTL = 0; // Select lowest DCOx and MODx settings

BCSCTL1 = CALBC1_1MHZ; // Set DCO

DCOCTL = CALDCO_1MHZ;

P2DIR |= 0xFF; // All P2.x outputs

P2OUT &= 0x00; // All P2.x reset

P1SEL |= RXD + TXD ; // P1.1 = RXD, P1.2=TXD

P1SEL2 |= RXD + TXD ; // P1.1 = RXD, P1.2=TXD

P1DIR |= RXLED + TXLED;

P1OUT &= 0x00;

UCA0CTL1 |= UCSSEL_2; // SMCLK

UCA0BR0 = 0x08; // 1MHz 115200

UCA0BR1 = 0x00; // 1MHz 115200

UCA0MCTL = UCBRS2 + UCBRS0; // Modulation UCBRSx = 5

UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**

UC0IE |= UCA0RXIE; // Enable USCI_A0 RX interrupt

__bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ int until Byte RXed

while (1)

{ }

}

#pragma vector=USCIAB0TX_VECTOR

__interrupt void USCI0TX_ISR(void)

{

P1OUT |= TXLED;

UCA0TXBUF = string[i++]; // TX next character

if (i == sizeof string - 1) // TX over?

UC0IE &= ~UCA0TXIE; // Disable USCI_A0 TX interrupt

P1OUT &= ~TXLED; }

#pragma vector=USCIAB0RX_VECTOR

__interrupt void USCI0RX_ISR(void)

{

P1OUT |= RXLED;

if (UCA0RXBUF == 'a') // 'a' received?

{

i = 0;

UC0IE |= UCA0TXIE; // Enable USCI_A0 TX interrupt

UCA0TXBUF = string[i++];

}

P1OUT &= ~RXLED;

}