source: PlatformSupport/User_IO/examples/UserIO_Sound_Demo.c

#include <string.h>
#include "ascii_characters.h"
#include "warp_userioboard_util.h"
#include "Sound_Test.h"
#include "xparameters.h"

#define CLKFREQ 50000000

#define MIDDLE_A (CLKFREQ / 440)
#define LOUD 7500

int main()
{
    xil_printf("Starting Sound v00.1\r\n");

    int i, status;
    unsigned int trackball, trackball_prev;

    unsigned char buzzer_en = 0;
    unsigned int buzzer_duty = LOUD;
    unsigned int buzzer_period = MIDDLE_A;

    warp_userioboard_buzzer_set(buzzer_period, buzzer_duty);

    //Initialize the LCD for slot 1 (i.e. don't flip the image) and non-inverted colors
    warp_userioboard_lcd_init(1, 0);

    while(1)
    {
        trackball_prev = trackball;
        //Read the trackball inputs
        trackball = warp_userioboard_get_trackball();

        switch(trackball ^ trackball_prev)
        {
            case TRACKBALL_PUSH:
                if(trackball & TRACKBALL_PUSH)
                    buzzer_en = buzzer_en ^ 1;
            break;
            case TRACKBALL_UP:
                if(trackball & TRACKBALL_UP)
                    buzzer_period = buzzer_period + 2500;
            break;
            case TRACKBALL_DOWN:
                if(trackball & TRACKBALL_DOWN)
                    buzzer_period = buzzer_period - 2500;
            break;
            case TRACKBALL_RIGHT:
                if(trackball & TRACKBALL_RIGHT)
                    buzzer_duty = buzzer_duty + 250;
            break;
            case TRACKBALL_LEFT:
                if(trackball & TRACKBALL_LEFT)
                    buzzer_duty = buzzer_duty - 250;
            break;
            default:
            break;
        }

        warp_userioboard_set_buzzer_en(buzzer_en);
        warp_userioboard_buzzer_set(buzzer_period, buzzer_duty);
    }
    
    return 0;
}