title: Change UIButton Background Image more than once per second
body: <p>I am currently working with the iPhone SDK.</p>
  
  <p>I have a NSTimer that changes the background image of a UIButton.
  Once this is complete, it will trigger the same action again (reset the NSTimer) for a predetermined number of times.</p>
  
  <p>My problem is that if my NSTimer is set to execute more than once per second. (0.75, say) The background image wont change.</p>
  
  <p>I am using NSLog to check that the event fires. But the button image will just remain in its original state.</p>
  
  <p>Is there any way to change the background image more often than once per second?</p>
  
  <p>This is my timer :</p>
  
  <pre><code>[NSTimer scheduledTimerWithTimeInterval: tmpLvlSpeed
                                       target: self
                                     selector: @selector(simPressRed:)
                                     userInfo: nil
                                      repeats: NO];
  </code></pre>
  
  <p>And the code to change the image:</p>
  
  <pre><code>[btnRed setImage:[UIImage imageNamed:@"btn_red.png"] forState:UIControlStateNormal];
  </code></pre>
  
  <p>if tmpLvlSpeed is less than 1.0, the button image will never change. Even though the simPressRed function will still fire.</p>
  
  <p>Any clues? Is there an update cycle I can modify?</p>