Problems this weekend VBOX Sport and GoPoint BT1 autocross

[gplracerx]

Crash Logs attached. HLPTRL file in the mail

Problems:

Accelerometer never calibrated in video mode.
Data link to VBOX sport was only solid for one of the three runs. The first run claims to be on the internal GPS, but that doesn't exist and the data was far too good. The third run reported only 10 Hz rather than 20.
The VBOX Sport logged the first run on its internal SD card, but none of the rest. I'm assuming that means that it doesn't log internally when connected to HLT.
OBDII data all over the map.

[gplracerx]

I think that the problem with the GPS data in the third run (LAPINDEX 4) was that the external antenna became disconnected from the VBOX Sport. That still doesn't explain the 64,000+ rpm readings, though.

[Harry]

Looks like a odd collection of sensor connection issues... Looking into the OBD data, the only theory I have is OBD input dropped out (the 01:14.91 receive OBD fixes for the first third only, the rest in extrapolated (except rpm, which is still delivered), the 01:16.55 had a drop out for the 4th fifth of the distance recorded). I will recheck interpolation / extrapolation for OBD again, especially in cases the GPS update rate is a lot higher than the OBD rate. The GPS data for all three laps sent is delivered from the VBOX (I can see that from the time stamps), but a lot of fixes do not arrive. Not sure the reason is the antenna cable, looks more like an BT overload. This results in the update rates shown (4, 20, 10Hz). The crash logs are not related to all of this, they show some database issues.

As the biggest issue is definitively the flaky BT connection, can you please recheck your configuration? Just reboot everything, connect the VBOX and the BT1, and watch the Sensor List in LapTimer. Do you get the usual update rates here (20 Hz for the VBOX and something between 2 and 8 Hz for the BT1)? Do you have any other BT enabled devices in your car? In case you have, please disable them.

- Harry

[Harry]

FYI: Did some checks on your OBD data. LapTimer usually uses interpolation to get valid OBD values store aside of GPS fix data. As OBD data has not been delivered for several seconds in some areas (named connection problems), LapTimer ran into situations it actually extrapolated OBD data far beyond the last OBD fix received. Consider the example the last two OBD fixes delivered show 1000 rpm at t and 900 rpm at t[i+1]. In case LapTimer does not receive a value for t[i+2] it will extrapolate the rpm value to 800, 700, and so on. In this example, LapTimer will be at 0 after 9 missing fixes and will cross zero afterwards. This produces actually an overflow resulting in these 64000+ values for rpm. One could argue LapTimer should actually turn off extrapolation at some time (and I will add this), but actually it is working around a pathological case data wise...

- Harry

[gplracerx]

My phone Bluetooth is on and shows up on the iPod Bluetooth list as available, but it wasn't paired. I'll try turning it off as well as Bluetooth in the car, which is paired with the phone.

[Harry]

Don't believe the first one will disturb much, the second definitively will. VBOX+BT1 already adds a small penalty to the BT1's update rate (1 Hz), additional traffic (even simple stay alive communication) will have an impact.

Harry

[gplracerx]

I'm pretty sure it's the antenna. Look at the number of satellites. In the first two runs, it's 9 or 10. But right at the end of the second run it suddenly drops to 3. Then in the third run it's about five but varies from a high of 8 to a low of 3. I had to rearrange the wire because I had a passenger on the second run and I think I put some strain on the wire that eventually caused it to be disconnected. I found it was disconnected when I was packing up the car to go home.

[gplracerx]

The BT1 was running at 3Hz and would drop out occasionally to 0 Hz. No other Bluetooth devices were running in the car. I unpaired and reconnected the BT1 and rebooted the iPod. The BT1 was running at 5Hz with the VBOX off and 4HZ with it on. I need to drive around some more and see if it still drops out. I'm trying a different throttle PID. I'll let you know how that works out and which one seems best.

[Harry]

For the 0 Hz OBD drop outs: please check if you get a red indicator in the OBD Gadget ("Engine ..." in e.g. GPS View) from time to time. This would be an indicator it is not about a bluetooth issue, but a protocol problem between LapTimer and your car.

- Harry

[gplracerx]

The OBD rate box does turn red when it goes to 0 Hz.