BT GPS connection, low device update rate?


Have been happy Racechrono used for several years with RR trackdays. This summer I started to have issues, same phone and same BT GPS as last season...

First I noticed that the system is not recording all the laps, connection seems to work but after 10-12 laps set there is only 2 laps recorded. Then started to look more carefully about the data and noticed that my BT GPS update rate is extremely low. It should be around 10 Hz, but actual numbers are around 0.3-0.6 Hz. Last season the recording was happening more or less with full 10Hz rate. This might be reason also on the missing laps on some sessions (or might not be...).

I started to figure out if there would be any means to restore the connection by changing setting. The power saving schemes on the Android has been updated recently and I turned all the recommended settings on (Performance mode, application specific settings). This did not help on this issue. Then removed the BT pairing, re-installed the Racechrono, but not with permanent luck but with some improvement. For 2 laps the system was able to use the 10Hz again, but during the same session it did not record all laps, missed ~8-9 ones... One interesting observation, I have seen that after the new pairing is done and starting a new session and when the GPS fix is established, for short time (few seconds) the system shows 10Hz at the detailed view, but it will drop to low 0.3-0.6Hz rate. That few seconds kind of reminds me of the power saving enabling, but cannot be sure.

But how to investigate this more? Is there any ways to have some log enabled to see what is going on here? My system is Huawei Honor 8 Lite (Android version 8.0.0, PRA-LX1 build), Qstar BT-Q818XT in 10Hz mode, Racechrono Pro 6.0.8.

This is the best SW for lap timing, but this issue needs to be fixed. I can try to help by getting logs or anything else that would help if needed. Has anyone else noticed this same issue? I know that my teammate sees the same issue with different type of BT GPS and different model phone so I am not totally alone with this.



  • edited July 2019
    Two possibilities:

    1) New power saving measures by the phone. Something that many times can be turned off in the phone's power saving settings. Usually they do not affect apps on the foreground (basically using the app screen turned on, and the app visible).

    2) The phone has new Bluetooth stack or driver through the system updates. These are then slighly more incompatible with the Qstarz BT-Q818XT, which is already known to be problematic since Android 5.0... And the problem always causes bad update rate, like you just described. This is the reason why this GPS is not on my recommended list.

    I'll try to source a phone like yours and test same combination.
  • Thanks aol for quick response! Here are my five cents:

    1) I assume this would not be the case as the screen is on when the rate drops. Still, there might be some power saving enabling that point... But like wrote, I did change the Settings - Apps - Racechrono - Battery - Manage manually. Could not find anything else that might affect on this, am I right?

    2) This is my assumption too. Something changed at the BT stack which now breaks the data rate. But, it might be stack internal power saving feature as the 10Hz communication works for a short while. I know that the BT-Q818XT is not the easiest in this sense, but my team mate is using different BT (some 5Hz device) with same symptoms so would not totally blame the Qstar at this point...
  • @ziili, the other GPS might be using the same chipset, I know there has been several on different brands. Usually though, configuring the 818XT to 5 Hz has fixed or at least improved the situation.

    I've ordered a Huawei Honor 8 Lite for testing this. I have plenty of different GPS to test this.

    If you want to test some stuff related to this, you can first try your GPS in 1 Hz mode. It has a switch for this. See if the update rate drops from 1 Hz. Then you could test it in 5 Hz mode by configuring it with Qstarz PC configuration software. Finally you should try the GPS with another Android phone.
  • @aol, tested today leaving the 818XT to 1Hz mode by the selection switch. Same issue was seen, but the 1Hz data rate stayed stable longer time than the 10Hz mode, but still it was dropping to 0.3-0.5Hz in 5-6s.

    I can try to configure the 818XT to the 5Hz mode, but assumption is that as the 1Hz was not working the 5Hz would work neither properly...

    You have a great dedication to solve this issue as you have ordered same phone to do the testing, kudos for that!!!!
  • edited July 2019
    @ziili, it looks like a bug in the firmware, Bluetooth specific. Firmware worked perfectly for one 5 minute session and is immediately broken just like you describe. Tested GPS was Qstarz BT-Q818XT just like yours.

    Notice that you get 10 Hz initially, but the clock is already running slow. It just takes few seconds to fill the transmit buffer, and start dropping data.

    Here's my quick tests with the broken firmware:

    Old GPS with roughly similar hardware as your GPS:

    - Qstarz BT-Q818XT broken
    - Qstarz BT-Q818X broken, same chipset
    - Qstarz BT-Q818 broken, same chipset
    - Holux M1000B broken, same chipset
    - iBlue 747 works (5 Hz), a bit surprising as I thought it's same hardware as Q818X but I guess not

    Some modern Bluetooth GPS receivers:

    - Garmin GLO works (7 Hz)
    - Garmin GLO 2 works (7 Hz)
    - Dual XGPS 160 works (10 Hz)
    - Dual XGPS 150 works (5 Hz)
    - Holux RCV-3000 works (1 Hz)
    - Qstarz BL-1000GT works (9 Hz), BLE device so really didn't expect any problem here :)

    So my summary would be that firmware on Huawei Honor 8 Lite is broken, so that it has become incompatible with Qstarz BT-Q818 series GPS receivers. I have contact at Qstarz so maybe they can contact Huawei about this. Other than that, there's no further action from me. Sorry to say that there's no quick fix.
  • Small update, my team mate device looks to be i-Blue 737 with different label (Racing GPS label), and looking from here it seems to be done with MTK chipset: So same manufacturer as the Qstar chipset (and assumption for iBlue 747 to be same MTK chipset). So this issue is affecting to all MTK based receivers?
  • edited July 2019
    It might be my tested receiver is actually iBlue 737, just remembering the name incorrectly. Anyway it looks like most MTK-II chipset devices are affected. I'm not sure if the Bluetooth chip is part of that chipset or is it just coincidence that they use the same chipset that has this problem.
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