Harry's GPS Suite Forum

When I use iPhone 14's internal GPS with GPS Storage Rate sets to 10 Hz, OBD data updates at 10 Hz.

If I use DUAL XGPS 160 with GPS Storage Rate sets to 10 Hz, OBD update rate gets much slower like 1 Hz to 2 Hz. Even worse, OBD update becomes very intermittent like if data was getting stuck. The System Status says OBD update rate is good (green) so that I didn't realize the data update issue until I download the data from HLT.

Is this due to the bandwidth limit of the Bluetooth transmision because two Bluetooth devices (PLX Kiwi 3 and DUAL XGPS 160) are running simultaneously?

Any solution or mitigation for using two Bluetooth devices at high update rate?

I set GPS Storage Rate to 10 Hz in order to get OBD data at that rate regardless of the GPS (especially required with the internal GPS).
I wonder if I should set it to "GPS Rate" even if DUAL XGPS 160 runs at 10 Hz anyway.

Are these OBD Tweaks you mentioned in other thread going to help?
OBD Tweaks / Adaptive Timing ‣ Enabled
OBD Tweaks / ECUs Addressed ‣ ECM
OBD Tweaks / Disable Parallel Requests ‣ YES

Yes, I assume this is a bandwidth issue. In a greenfield environment, with just the XGPS and an OBD adapter active, both will be able to achieve their full update rate. What I want to say is, that it may not be a conflict between the two but other BT devices around. To check, please install an app like LightBlue and scan for BT networks. Especially car stereo devices tend to broadcast discovery messages reducing available bandwidth significantly.

- Harry

If car stereo devices broadcast discovery messages that are enough to reduce available bandwidth, how can I see those messages on LightBlue?
The Log tab doesn't seem to show those messages.

I do not think it shows packages, it is just to see all BT devices around. In case you see a car stereo, make sure it is not in discovery mode or off. Car stereos have their own fuse mostly, so you can remove mute it completely to test if it is the culprit.

Any idea why the System Status doesn't warn if the OBD update rate is low in this case?

Does setting the "Storage Rate" to 10 Hz rather than "GPS Rate" have any negative impact on the OBD data rate when the GPS rate is 10 Hz?
The reason why I leave the "Storage Rate" to 10 Hz even if XGPS is 10 Hz is to prevent the OBD data rate from going down when for some reason GPS drops to the internal GPS that runs at 1 Hz.

A higher storage rate results in higher internal processing load. For a modern smartphone, it will not have any impact on rates achieved - the bottleneck is the wireless connection bandwidth.

After running into all those issues with XGPS and based on my test that I found XGPS is less accurate than iPhone's GPS for some reason, I decided to ditch XGPS and go back to iPhone's GPS. Thank you for your suggestion and help on this anyway.

Digging in the forums, I found the exact same problem reported a number of times already.
viewtopic.php?p=27861#p27861
https://www.youtube.com/watch?v=RKsuf2QNIWo

So I'm actually running into this data fusion problem where the OBD data gets choppy and stepped.
It's been several years since all those problems were reported but no solution for this data fusion yet so far?

If the data fusion problem is caused due to the update rate or the difference in the cadence of the two data streams (OBD 7~12 Hz vs GPS 10 Hz), using a higher storage rate say 20 Hz may mitigate the problem because all the data will be oversampled?