Question

Write a complete and concise TI-MSP432 C program with suitable comments that would allow the usage of an onboard push button to control the onboard RGB LEDs so that they cycle through the following patterns: only R on, only G on, only B on. An LED stays on until the push button is pushed again. Do not use any of the low power modes. There will be penalty on un-necessary codes.

Answer 1

You can control the color of the 3-color LED by using analogWrite() and using a value of 0-255 for each of the three pins that control the LED. For the MSP432 Those pins are named: RED_LED, GREEN_LED, and BLUE_LED.

The single-color red LED (named LED1) can only have its color changed by desoldering the current LED and replacing it with a comparably specced LED of the color you desire. (This is probably not what you wanted, but I included it just in case it was.)

Here's a quick snippet that creates a purplish color:

analogWrite( RED_LED , 64 ); // PWM at about one quarter intensity

analogWrite( BLUE_LED , 64 ); // PWM at about one quarter intensity

analogWrite( GREEN_LED , 0 ); // full off

And the color orange would be a tiny bit of green and blue, combined with a little red.

#include <io.h>
#include <signal.h>

#define BUTTON BIT3 // Port 1.3
#define REDLED BIT0 // Port 1.0
#define GRNLED BIT6 // Port 1.6

int doflip = 1;

int main(void) {
// Watchdog setup
WDTCTL = WDTPW + WDTHOLD; // stop watchdog (password + hold counter)

// LED initial setup
P1DIR |= REDLED + GRNLED; // set P1.0 and P1.6 as output (1) pins
P1OUT |= REDLED; // Enable REDLED
P1OUT &= ~GRNLED; // Disable GRNLED

// Button setup
P1DIR &= ~BUTTON; // button is an input
P1OUT |= BUTTON; // pull-up resistor
P1REN |= BUTTON; // resistor enabled
P1IES |= BUTTON; // interrupt on low-to-high transition
P1IE |= BUTTON; // interrupt enable

// Timer setup
BCSCTL3 |= LFXT1S_2; // Set clock source to VLO
TACCR0 = 2500; // Count to this, then interrupt
TACTL = TASSEL_1 | MC_1; // Clock source ACLK
TACCTL1 = CCIE; // Timer A interrupt enable

// Shut down CPU, General Interrupt Enabled
__bis_SR_register(CPUOFF | GIE);
return 0;
}

interrupt(TIMERA1_VECTOR) ta1_isr(void) {
TACCTL1 &= ~CCIFG; // reset the interrupt
if (doflip)
P1OUT ^= (REDLED + GRNLED); // flip LED output
}

interrupt(PORT1_VECTOR) port1_isr(void) {
P1IFG = 0; // reset interrupt
doflip ^= 1; // toggle LED flipping
}