MSP430 Workshop notes 2/27/2011

Here are the notes from our TI MSP430 programming workshop, held 2/27/2011. Our goal was to get working build environments on our PCs and be able to program the LED on the ez430 development sticks from Texas Instruments. We succeeded!

Code

Here's the blinky code we used to test the toolchain, modified from TI's blinky code to make it more readable for non-C programmers:

#include <msp430x20x3.h>

void main(void)
{
	// The watchdog timer will periodically reset the chip if we haven't poked it
	// Initialize the WDT (WDTPW) and turn that behavior off (WDTHOLD)
	WDTCTL = WDTPW + WDTHOLD;

	// Mark P1.0 as an output pin by setting P1DIR's LSB to 1
	P1DIR = P1DIR | 0x01;

	while (1)	// Infinite loop
	{
		// Flip LED state
		// Invert pin P1.0, port 1 bitwise XOR with 0000 0001
		P1OUT = P1OUT ^ 0x01;

		// Wait
		i = 20000;
		while ( i > 0 ) {
			i--;
		}
	}
}

And here's some code that can make the LED pulse up and down, rather than flash on and off:

#include <msp430x20x3.h>

// Constants for pulse width increment and cycle time (sum of LED on + off time)
#define INCR  1
#define CYCLE 250

void main(void)
{
	// The watchdog timer will periodically reset the chip if we haven't poked it
	// Initialize the WDT (WDTPW) and turn that behavior off (WDTHOLD)
	WDTCTL = WDTPW + WDTHOLD;

	// Mark P1.0 as an output pin by setting P1DIR's LSB to 1
	P1DIR = P1DIR | 0x01;

	// Starting value for the LED pulse width
	unsigned int width = 11;

	// Per-cycle pulse width delta (how much longer to stay lit each cycle)
	unsigned int incr = INCR;

	// Loop counter
	unsigned long i;

	while (1)	// Infinite loop
	{

		// == LED ON ==
		// Turn on pin P1.0, port 1 bitwise OR with 0000 0001
		P1OUT = P1OUT | 0x01;

		// Wait
		i = width;
		while ( i > 0 ) {
			i--;
		}

		// == LED OFF ==
		// Turn off pin P1.0, port 1 bitwise AND with 1111 1110
		P1OUT = P1OUT & 0xFE;

		// Wait out the remainder of the cycle
		i = CYCLE - width;
		while ( i > 0 ) {
			i--;
		}

		// == UPDATE PULSE WIDTH ==
		width += incr;

		// If we've hit the minimum or maximum pulse width, start moving the width
		// in the other direction
		if ( width >= CYCLE - 30 || width < 1) {
			incr = -incr;
		}

	}
}

Links

Tools

• mspgcc4 (sourceforge.net)
  • Extract the latest tarball, run ./build_gcc.sh
  • Will download binutils, gcc, gdb, and compile them (may take a LONG time)
  • Will default to installing under /opt/

• mspdebug (sourceforge.net)
  • In Ubuntu, first install dependencies: apt-get install libreadline-dev libusb-dev
  • Put the 'mspdebug' binary in the bin/ directory established when you installed mspgcc4

Info

• MSP430 USB Stick user's guide (ti.com)
  • Schematic of development board
  • Notes on device capabilities

• Step by Step Guide To MSP430 Programming with Eclipse under Linux (43oh.com)
  • Used mspdebug in the console to program/debug the chip
  • We didn't try mspdebug + Eclipse as documented on this page, but would expect it to work well
  • Couldn't get Eclipse to connect to the msp430-gdbproxy instance and debug on the device
  • In the latest version of Eclipse, if using msp430-gdbproxy, use the debugger type "gdbserver Debugger" instead of "remote gdb/mi"

• TI Launchbread, a practical example of wiring/coding/flashing (simpleavr.com)

• MSP430 basic coding & programing part 1 (justinstech.org)

• MSP430 basic coding & programing part 2, watchdog timer examples (justinstech.org)