CPU (resources) usage

I suppose using a 5Hz GPS receiver brings a high amount of data processing.
Personally, I own a N95 8Gb, which is quite powerful in the Nokia smartphone range, but I really do not have any idea on the impact of RaceChrono on it. Is the N95 CPU powerful enough ? Does the bandwidth between the phone and GPS receiver wide enough ? Is there any bottleneck, if so, which one ?

Do you know if the hardware of some smartphones is a little bit short, if so, could you give us a matrix with recommendations about which kind of smartphone is good for a 5Hz GPS receiver, which one is known to be good only for 1Hz, etc.

My question comes from something I noticed when testing statically my new 818X. When running a fake session, I switched to Live Timer, and started to look at the "GPS time" counter. I figured out it wasn't regular, sometimes freezing... I do not know what the reason is, but I though it may be due to the difficulty to process data at the right speed.


  • I'm using the same setup (N95 8GB & BT-818X). My timestamps (according to the CSV output) are on the button. Are you running any software in the background? I don't run any background apps but when I've used Google's app, I notice the phone slows down quite badly.
  • edited July 2009
    If you look at the GPS time and it's freezing, there is problem with the Bluetooth connection.

    What kind of 5 Hz do you have? If you have set the GPS to 5 Hz via some software, it can run out of bandwidth. Try so that you enable only GGA and RMC sentences to 5 Hz and GSA and GSV would be only 1 Hz? Others are not needed.

    Might also be some kind other Bluetooth problem.

    RaceChrono uses a lot of CPU when drawing the maps etc (traveled route). Otherwise it draws power mainly due it tries to keep backlight on and the Bluetooth connections.
  • I did not try a "real" session (I mean while driving/moving). I was static and only had a look at the "GPS Timer" screen (when you toggle the live timer screen), this one refreshing every 0.2s in my 5Hz case. Maybe that's a wrong problem, but I found a little bit strange not to have a fluid "GPS Timer" sequence of values.

    My GPS receiver is a Qstarz 818X, right out of the box. I didn't modify any value like GGA, RMC, GSA, ... but I'll have a look at them. I set the 5Hz mode with the switch on the side of the GPS case.

    And I never let any program running at the same time.

    My question was quite open : are the smartphone like N95 powerful enough to handle the data processing coming from a 5Hz GPS unit ? And do you know what is the first bottleneck ? CPU ? Bluetooth bandwidth ? any other ?
  • I set it up as recommanded (GSA and GSV at 1 Hz, others at 5Hz).
    GPS Time is still freezing time to time, as previously mentionned (it freezes for at max 1 sec).
    But, I had a closer look at the data in Traveled route and despite the fact that GPS time lags, Traveled route data are all there (every 0.2 sec I've got something).

    Maybe the problem is only related to GPS time display ?

    Note that I've also have the same behavior when setting the GPS to 1Hz (it freezes every 5-6 seconds).
  • Ok, so no Bluetooth problem then if you can see every 0.2sec in the Traveled Route. Sorry for mis-diagnosis :-)

    One thing that comes to mind is that can you try to switch the "Storage selection" to your Phone memory (C:) just for testing? Maybe your memory card is slow for reason or another.

    Also it might be you're running some background app that is freezing.
  • edited July 2009
    In fact it happens even if I change the storage device (I set C: instead of E:) and using the internal GPS results in the same behavior.

    I have really no other program running (I switched off JBAK, Google Search, RotateMe, T9Nav, ... and all of these background tasks) and I still see the display freezing.

    But if it doesn't affect the main purpose of RaceChrono (logging timestamped information about position), so it may be ignored, just a weird thing...

    As in my initial post my main question was : "is my smartphone powerful enough for my new 5Hz GPS receiver ?" I think I've got the answer : "yes, it is, just don't rely on the GPS Time display, everything else works fine."

    I just wonder if I'm the only one noticing this on a N95.
  • Well your smart phone _should_ be powerful enough to have smooth timer as well :) The Nokia N95 is quite highly speced compared to some other phones, where I've seen it running just fine, with even bigger resolutions (like Nokia E60, E70).

    On my N95 I have no problems.
  • strange. My N95 is quite normal : 8Gb version, fw 30.0.018, hacked and a few apps installed here and there.

    Gps time is not my priority if everything else works fine:)

    Thank you for trying to find the reason.
  • OK, let me know if you figure out what might be causing it :)
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