Difficulty in generating square wave using DM3730

I made the following program for generating the square wave using DM3730 but i get a lot of jitter in generation of square wave
and do not get the required frequency even. Please look into it and suggest methods immediately.

My observation 

for usleep = 10^6, I get 0.5 hertz
for usleep = 10^4, I get 50 hertz
for usleep = 10^2, I get 1.5 Kilo hertz,
for usleep = 1, I get 1.5 Kilo hertz,

Please suggest some program to generate square wave faithfully upto a frequency of 10MHz or so....

#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

int main() {

  int fd = open("/dev/mem", O_RDWR | O_SYNC);

  if (fd < 0) {
    printf("Could not open memory\n");
    return 0;
  }

  // Pad configuration
  volatile ulong *pinconf;
  pinconf = (ulong*) mmap(NULL, 0x10000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0x48000000);
  if (pinconf == MAP_FAILED) {
    printf("Pinconf Mapping failed\n");
    close(fd);
    return 0;
  }

   // Configure ONE Expansion HEADER PIN AS OUTPUT FOR SOC.
  //CONFIGURE ONE EXPANSION HEADER PIN AS OUTPUT FOR EOC
  //CONFIGURE ONE EXPANSION HEADER PINS AS BIDIRECTIONAL



  pinconf[0x2158/4] = 0x011C011C; //PIN CONFIGURED AS BIDIRECTIONAL
  pinconf[0x215C/4] = 0x011C011C; //PIN CONFIGURED AS
  pinconf[0x2160/4] = 0x011C011C; //PIN CONFIGURED AS  
  pinconf[0x2164/4] = 0x011C011C; //PIN CONFIGURED AS
  pinconf[0x2168/4] = 0x011C011C; //PIN CONFIGURED AS
  pinconf[0x216C/4] = 0x011C011C; //PIN CONFIGURED AS
  pinconf[0x2170/4] = 0x011C011C; //PIN CONFIGURED AS
  pinconf[0x2188/4] = 0x011C011C; //PIN CONFIGURED AS  
  close(fd);

 
  fd = open("/dev/mem", O_RDWR | O_SYNC);
 
  // GPIO Configuration: configure are input ---FOR ADC INPUT DATA
  volatile ulong *gpio;
  gpio = (ulong*) mmap(NULL, 0x10000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0x49050000);
  if (gpio == MAP_FAILED) {
     printf("Gpio Mapping failed\n");
     close(fd);
     return 0;
  }

  // Configure all GPIO pins on bank 5 as OUTPUT
  gpio[0x6034/4] = 0x00000000;
  int c=0;
  int count;
  for(;;) {
      gpio[0x603c/4] = 0xffffffff;
      usleep(1);   
      gpio[0x603c/4] = 0x00000000;
      usleep(1);   
  }
}