/* Sound the speaker at 440Hz
 *
 * The speaker is connected to PORTC 4.
 * Default clock 50 MHz is used.
 * Delay loop is used for time interval. The number
 * of delay cycles is determined empirically. 
 *
 * Built and tested with Keil MDK-ARM v5.24a and TM4C_DFP v1.1.0
 */

#include "TM4C123.h"

void delayUs(int n);

int main(void) {
    volatile unsigned char readback;

    // enable PORTC 4 as output
    SYSCTL->RCGCGPIO |= 0x04;       // enable clock to GPIOC
    readback = SYSCTL->RCGCGPIO;    // make sure the clock is enabled
    GPIOC->AMSEL &= ~0x10;          // disable analog function of PORTC 4
    GPIOC->DIR |= 0x10;             // set PORTC 4 as output pins
    GPIOC->DEN |= 0x10;             // set PORTC 4 as digital pins

    for (;;) {
        GPIOC->DATA |= 0x10;        // turn on PB2, 0
        delayUs(1184);
        GPIOC->DATA &= ~0x10;       // turn on PB3, 1
        delayUs(1184);
    }
}

/* delay n microseconds (50 MHz CPU clock) */
void delayUs(int n) {
    int i, j;
    for(i = 0 ; i< n; i++)
        for(j = 0; j < 6; j++)
            {}  /* do nothing for 1 ms */
}