/*
 * Sound the speaker at 440Hz
 * The speaker is connected to PORTC 4.
 * Default system clock 16 MHz is used.
 */

#include "TM4C123GH6PM.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 PC4
        delayUs(1136);
        GPIOC->DATA &= ~0x10;       // turn on PC4
        delayUs(1136);
    }
}

// delay n microseconds (16 MHz CPU clock)
void delayUs(int n)
{
    int i, j;
    for(i = 0 ; i < n; i++)
        for(j = 0; j < 3; j++)
            {}  // do nothing for 1 us
}

// This function is called by the startup assembly
// code to perform system specific initialization tasks.
void SystemInit(void)
{
    // Grant coprocessor access
    // This is required since TM4C123G has
    // a floating point coprocessor
    SCB->CPACR |= 0x00f00000;
}