[Zybo] Xilinx Hello World in C

/*****************************************************
Getting Started Guide for Zybo

This demo displays the status of the switches on the
LEDs and prints a message to the serial communication
when a button is pressed.

Terminal Settings:
   -Baud: 115200
   -Data bits: 8
   -Parity: no
   -Stop bits: 1

1/6/14: Created by MarshallW
****************************************************/

#include <stdio.h>
#include "platform.h"
#include <xgpio.h>
#include "xparameters.h"
#include "sleep.h"

int main()
{
   XGpio input, output;
   int button_data = 0;
   int switch_data = 0;

   XGpio_Initialize(&input, XPAR_AXI_GPIO_0_DEVICE_ID); //initialize input XGpio variable
   XGpio_Initialize(&output, XPAR_AXI_GPIO_1_DEVICE_ID);    //initialize output XGpio variable

   XGpio_SetDataDirection(&input, 1, 0xF);          //set first channel tristate buffer to input
   XGpio_SetDataDirection(&input, 2, 0xF);          //set second channel tristate buffer to input

   XGpio_SetDataDirection(&output, 1, 0x0);     //set first channel tristate buffer to output

   init_platform();

   while(1){
      switch_data = XGpio_DiscreteRead(&input, 2);  //get switch data

      XGpio_DiscreteWrite(&output, 1, switch_data); //write switch data to the LEDs

      button_data = XGpio_DiscreteRead(&input, 1);  //get button data

      //print message dependent on whether one or more buttons are pressed
      if(button_data == 0b0000){} //do nothing

      else if(button_data == 0b0001)
         xil_printf("button 0 pressed\n\r");

      else if(button_data == 0b0010)
         xil_printf("button 1 pressed\n\r");

      else if(button_data == 0b0100)
         xil_printf("button 2 pressed\n\r");

      else if(button_data == 0b1000)
         xil_printf("button 3 pressed\n\r");

      else
         xil_printf("multiple buttons pressed\n\r");

      usleep(200000);           //delay

   }
   cleanup_platform();
   return 0;
}