Stellaris LaunchPad Code Examples: How To Use The RGB LED For Digital Output

Watch the video and/or get the code below.

Relevant Links:

• Stellaris LM4F120H5QR Microcontroller Data Sheet
• Stellaris LM4F120 LaunchPad Evaluation Board User Manual

Blink The Red LED Code:

#include <lm4f120h5qr.h>

void wait(void);

int main()
{
    // General-Purpose Input/Output Run Mode Clock Gating Control (RCGCGPIO), pg. 315
    SYSCTL_RCGCGPIO_R |= 0x20U; // activate the clock for port f
    
    // GPIO Lock (GPIOLOCK), pg. 645
    GPIO_PORTF_LOCK_R = 0x4C4F434BU; // unlock the lock register 
    
    // GPIO Commit (GPIOCR), pg. 646
    GPIO_PORTF_CR_R = 0xFF; // enable commit for PORT F 
    
    // GPIO Analog Mode Select (GPIOASMSEL), pg. 648
    GPIO_PORTF_AMSEL_R = 0x00U; // disable analog functionality 
    
    //  GPIO Port Control (GPIOPCTL), pg. 649
    GPIO_PORTF_PCTL_R = 0x00000000U; // configure port f as GPIO
    
    // GPIO Direction (GPIODIR), pg. 624
    GPIO_PORTF_DIR_R = 0x0EU; // 0xE = 01110 make PF3, PF2, and PF1 output
 
    // GPIO Alternate Function Select (GPIOAFSEL), pg. 633
    GPIO_PORTF_AFSEL_R = 0x00U; // disable alternate functions
    
    // GPIO Digital Enable (GPIODEN), pg. 643
    GPIO_PORTF_DEN_R = 0xFFU; // enable digital on all pins in PORTF
    
    while(1)
    {

        GPIO_PORTF_DATA_R &= ~0x0E; // 0E = 00001110, so ~0E = 11110001 turn off the three leds
        wait();
        GPIO_PORTF_DATA_R |= 0x02; // turn on the red led
        wait();
    }
   
    return 0;
}

void wait(void)
{
  for(int i=0;i<1000000;i++);
}