firmware for an arduino based usb arrow keypad

ArrowKeys.pde

#include "UsbKeyboard.h"

#define BUTTON_PIN_RIGHT 9
#define BUTTON_PIN_LEFT  10
#define BUTTON_PIN_UP    11
#define BUTTON_PIN_DOWN  12

#define KEY_ARROW_RIGHT 0x4F
#define KEY_ARROW_LEFT  0x50
#define KEY_ARROW_UP    0x51
#define KEY_ARROW_DOWN  0x52

// If the timer isr is corrected
// to not take so long change this to 0.
#define BYPASS_TIMER_ISR 1

int send_stroke = 0;
int right_down = 0;
int left_down = 0;
int up_down = 0;
int down_down = 0;

void setup() {
  pinMode(BUTTON_PIN_RIGHT, INPUT);
  digitalWrite(BUTTON_PIN_RIGHT, HIGH);
  pinMode(BUTTON_PIN_LEFT, INPUT);
  digitalWrite(BUTTON_PIN_LEFT, HIGH);
  pinMode(BUTTON_PIN_UP, INPUT);
  digitalWrite(BUTTON_PIN_UP, HIGH);
  pinMode(BUTTON_PIN_DOWN, INPUT);
  digitalWrite(BUTTON_PIN_DOWN, HIGH);  
  
#if BYPASS_TIMER_ISR
  // disable timer 0 overflow interrupt (used for millis)
  TIMSK0&=!(1<<TOIE0); // ++
#endif
}

#if BYPASS_TIMER_ISR
void delayMs(unsigned int ms) {
   /*
  */ 
  for (int i = 0; i < ms; i++) {
    delayMicroseconds(1000);
  }
}
#endif

void loop() {
  send_stroke = 0;
  
  UsbKeyboard.update();

  digitalWrite(13, !digitalRead(13));

  if (digitalRead(BUTTON_PIN_RIGHT) == 0) {
    if (!right_down){
      UsbKeyboard.sendKeyStroke(KEY_ARROW_RIGHT);
      send_stroke = 1;
    }
    right_down = 1;
  } else {
    right_down = 0;
  }

  if (digitalRead(BUTTON_PIN_LEFT) == 0) {
    if (!left_down){
      UsbKeyboard.sendKeyStroke(KEY_ARROW_LEFT);
      send_stroke = 1;
    }
    left_down = 1;
  } else {
    left_down = 0;
  }

  if (digitalRead(BUTTON_PIN_UP) == 0) {
    if (!up_down){
      UsbKeyboard.sendKeyStroke(KEY_ARROW_UP);
      send_stroke = 1;
    }
    up_down = 1;
  } else {
    up_down = 0;
  }

  if (digitalRead(BUTTON_PIN_DOWN) == 0) {
    if (!down_down){
      UsbKeyboard.sendKeyStroke(KEY_ARROW_DOWN);
      send_stroke = 1;
    }
    down_down = 1;
  } else {
    down_down = 0;
  }
   
  if (send_stroke) {
#if BYPASS_TIMER_ISR  // check if timer isr fixed.
    delayMs(20);
#else
    delay(20);
#endif
  }

}