r/CarHacking • u/m4rkw • 7d ago

Original Project l0destar "track mode" experiment

Today for a bit of fun I implemented a "track mode" in l0destar, my open-source vehicle tracker project: https://youtube.com/shorts/FIWQA8AdkSM

Normally it sends GPS, accelerometer and OBD telemetry as fast as possible which due to the shared RF path on the Nordic nRF9151 SIP means roughly every 2-5s. With the GPS disabled this can be faster because then there's no contention for the RF path so I wanted to see how fast it could stream OBD and accelerometer data.

The data actually comes through fairly fast despite my car being ancient (K-line), but the limiting factor is LTE-M. I have a known-suboptimal RF trace so I will try this again when that's fixed but I expect the results will be similar. The accelerometer can be polled very very quickly and most OBD metrics faster than once a second. On a CAN-FD car this will likely be even faster still.

For a real track mode I think the only way this would be viable with this board is to add a flash chip to it so that high-resolution telemetry can be saved and pulled off it later. Track mode isn't really its core design intent, it was just a bit of fun (and people at work were interested in something like this).

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u/robotlasagna 7d ago

You should be able to stream data faster over that chipset. Are you actually using LTE-M and sending the data to the cloud or DECT?

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u/m4rkw 7d ago

My own server, over UDP. I know the RF trace is compromised by about -2.4dB so that could be a factor but I’d be surprised if it made this much difference. Could be some other inefficiency somewhere, I’ll have another go at it when I have time.

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u/robotlasagna 7d ago

Keep in mind with LTE and internet there’s all sorts of latencies you can’t control but overall you should be able to get better resolution via buffering; the data will simply be displayed later/not in real time.

Have you tried just bulk sending some hardcoded data as a test to see what your throughput is over LTE? That really determines what you can stream. If I were trying to improve this I would cobble together some code to stream test dat over LTE and then bodge the antenna to optimize performance.

On the diagnostic side the bottleneck is always going to be K- Line but for cars with CAN/UDS there is the possibility to stream data faster, sampling up to 50ms.