Why is the amount of time needed to turn the screen on not always the same?

Question

This may very well be a nit-picking type of question about Android devices, and in particularly about the Samsung Galaxy SIII. The concern here, is of a UX nature. When the screen has gone blank to save the battery, and I click the power button, sometimes the screen turns on relatively quickly, othertimes more slowly. This happens also on relatively close carrying outs of such action (e.g. the screen goes blank, I press the power button, and the screen comes on quickly, then the screen goes blank to save power, I press the power button, but this time the screen comes on slowly).

The problematic usability scenario to consider is the following: sometimes, when the screen is taking longer than normal, my brain sends the signal to my hand to press the power button once more, thinking the reason the screen didn't come on is that I haven't pressed the button hard enough (especially since my phone's cover, made of plastic, makes such pressing even harder). However, as my thumb starts to press the button, but before I've completed the action, the screen comes on, and, as I complete the initiated press, the screen goes off again. So I must repeat this again. Sometimes the screen doesn't come on at all during such action because my thumb ends up finishing pressing the button just before the screen turns on, but the phone intercepts the keypress nevertheless and hence stays off. Every time this happens, I don't know if it's because the screen is taking too long to power on, if I haven't pressed the button hard enough, or if I've managed to press the button a second time just before the screen would have turned on, as a second attempt.

So my questions are:

• Why is the amount of time needed to turn the screen on not always the same?
• What's the best way to deal with the problem I described from the user's point of view?
• What about from the point of view of an electrical engineer/hardware designer7UX engineer?
• Is this problem dealt with in newer phones and fixed?

Thanks!!! :-)

Regards.

Answer 1

Here are your answers:

1. Depending on how many of the CPU cores are asleep (clocking at less than 200mHz for your phone), the system needs to wake up those. This takes time.
   If the device is not asleep (doing background work), the screen will turn on very quickly.
2. Best way to deal with: Don't use the power button to turn on the screen, but rather use the Home button. The Home button will not lock your phone and thus pressing it more than once doesn't have an impact on usability.
3. The hardware/electrical designer will tell you that conserving battery is slightly more important than quick screen-turn-on times. The UX engineer can't do anything about it. Making sure the system runs as it should does not depend on the hardware configuration (most notably the minimum clock rate/time until deep sleep ).
4. Newer phones may have a better kernel wake-up configuration, that turns on the screen faster (custom kernels for your phone can do that, too), but I can't promise anything.

It's a trade-off between battery and user experience.
I must admit that Samsung's TouchWiz has plenty problems like that one, which led me to switch to custom roms.