MSP430G2553 with XBee Module

Wireless & IoT
1

I am new to serial communication and have been running into some issues. I have been trying to interface my msp430g2553 chip with my XBee modules and have not had much success. Using RealTerm, I would like to be able to press a button on my protoboard and have the chip send a message to the terminal via XBee wireless communication. Also, I would like to send a value from the terminal to the chip and light up an LED on the board. I found this code online and attempted to modify it to do what I had in mind.

#include "msp430g2553.h"

#define BOUNCINGDELAY 250000

void main(void)
{
	WDTCTL = WDTPW + WDTHOLD;

	if(CALBC1_1MHZ == 0xFF || CALDCO_1MHZ == 0xFF)
		while(1);

	BCSCTL1 = CALBC1_16MHZ;
	DCOCTL = CALDCO_16MHZ;

	P1REN = BIT5;
	P1OUT |= BIT5;

	P2SEL = 0;
	P2SEL2 = 0;

	P2DIR |= (BIT0 | BIT1 | BIT2 | BIT3 | BIT4 | BIT5 | BIT6 | BIT7);
	P2OUT &= ~(BIT0 | BIT1 | BIT2 | BIT3 | BIT4 | BIT5 | BIT6 | BIT7);

	P1IE |= BIT5;
	P1IES &= ~BIT5;
	P1IFG &= ~BIT5;

	P1SEL = BIT1 | BIT2;		// P1.1 = RXD, P1.2 = TXD
	P1SEL2 = BIT1 | BIT2;		// P1.1 = RXD, P1.2 = TXD
	UCA0CTL1 |= UCSSEL_2;		// SMCLK
	UCA0BR0 = 138;				// 16MHz 9600
	UCA0BR1 = 0;				// 16MHz 9600
	UCA0MCTL = UCBRS_7;			// Modulation UCBRSx = 6
	UCA0CTL1 &= ~ UCSWRST;		// **Initialize USCI state machine**
	IE2 |= UCA0RXIE;			// Enable USCI_A0 RX interrupt

	_BIS_SR(GIE);
	
	while(1);
}

#pragma vector = USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR(void)
{
	switch(UCA0RXBUF)
	{
		case 1:
			P2OUT |= BIT0;
			P2OUT &= ~BIT7;
			break;
		case 2:
			P2OUT &= ~BIT0;
			P2OUT |= BIT7;
			break;
		default:
			P2OUT &= ~(BIT0 | BIT7);
	}
}

#pragma vector = PORT1_VECTOR
__interrupt void Port_1(void)
{
	if(P1IFG & BIT5)
	{
		int i = 0;
		char string[] = "Hello guys!";
		while(string[i] != '\0')
		{
			while(!(IFG2 & UCA0TXIFG));
			UCA0TXBUF = string[i];
			i++;
		}
		while(!(IFG2 & UCA0TXIFG));
		UCA0TXBUF = '\r';
		_delay_cycles(BOUNCINGDELAY);
		P1IFG &= ~BIT5;
	}
	P1IFG = 0;
}

Not only did this code not work for me, I ran into some peculiarities while experimenting with the board. I am using an XBee Explorer Regulated to attached one of the XBees to the protoboard. I removed the connection from my 9-Volt to the 5V pin on the Explorer and noticed that power was getting into the Explorer via the DOUT pin which is connected to the TXD pin of my chip? Maybe some information on how these pins are configured would be helpful? Furthermore, I have used X-CTU to configure both modules with the same baud rate. I have also been able to get the RSSI LED to light up on my boards XBee by sending a command through the terminal. Other than that, no message is sent to the terminal when I press the button and no LED lights up when the terminal sends to the board. Any information would be appreciated. Thanks!

2

Are the XBees Series 1 or Series 2? Vastly different products.

are the XBee’s in the transparent serial mode?

Same RF channel? Same PAN ID?

Both are end-devices? No PAN Coordinator?

COnfigured for no-association required?

DH:DL set to the other XBee’s address? And vice versa?

Using DIgi’s standard XBee firmware (virtual wire), you can eliminate the microprocessor if you wish. Connect push button to XBee DIO pin, configure accordingly to send message when button is pushed.

Some SFE XBee boards have a diode in series with the serial data line, in an invalid attempt at 5V to 3.3V level shifting.

3

Since you are new to serial comm on the msp430g2553, first directly connect (with an RS232 level translator, MAX232) the msp430g2553 to your PC. Once you can send the correct data from the msp430g2553 to the PC without the XBees then connect the XBees.

This way you only have one problem to solve at a time.