[Ovmsdev] Introduction - message replay and other topics

Ludovic LANGE ll-ovmsdev at lange.nom.fr
Mon Oct 10 06:34:46 HKT 2022

Hello everyone,

My name is Ludovic and I've just bought an OVMS for a R&D project I'm 
working on. I know how to read/write some (easy) code, and am not afraid 
of (digital) electronics too. I've managed to compile, and flash FW to 
this unit.

My use-case is to use OVMS as an aid during the testing phase / tuning 
of an EV vehicle:

  * Using OVMS as a pure data-logger of the CAN Bus (to SD card, with an
    automatic offload to a remote server as soon as a network connexion
    is available) - i.e. logging during the runs, and dumping the data
    either as soon as possible, or when the vehicle is back in the shop.
  * Also making use of the "dashboard" functions to have an in-vehicle
    display (phone/tablet) of the main parameters of interest : GPS
    Speed, Motor RPM, some BMS parameters, some controller parameters,
    ... so that the test driver can have some feedback on the internals
    of the vehicle.

Part of my plan is to explore the DBC-based vehicles of OVMS, and for 
that I was interested in using the "replay mode" that has been 
contributed to the code in 2019 : 
; however it does indeed look like a work in progress - as I wasn't able 
to make it replay something.

I've not delved much into the code (yet ?) but it looks that some 
implementations are incomplete (like `canplay_vfs::InputMsg`) and could 
explain that. But first I wanted to ask here what was your experience 
with this part - is it working for you in some state, even buggy ?

"replay mode" is not absolutely necessary but could be a huge time saver 
- otherwise I'd have to replay from another CANBus transceiver - and I'd 
prefer an integrated environment.

"replaying" is interesting for the setup phase as I'll be able to 
fine-tune the DBC setup ; have the metrics generated and then have the 
dashboard displaying "live" data - without needing a real vehicle test.

Also in the plan is to build a customized dashboard from a chosen set of 
metrics. This looks easy and well documented as far as I could tell, and 
I do not expect a lot of difficulties here ; what do you think ?

Also part of the plan would be to have a way to log to fixed-size files 
(either based on the number of events captured on the CANBus ; or based 
on the duration of the capture - like every 5 minutes) and to find a way 
to "rsync" them to a remote server. I do not intend to use the "server" 
connection (be it V2 or V3) as my use-case is a little bit different and 
I need to retrieve raw CANBus data, not processed metrics - for later 
post-processing (with SavvyCAN etc...). I'm open to any advices on the 
feasibility of this.

Finally, as a newcomer I'll also try to help with documentation on 
things that I struggled with or that are evident but not in the doc yet.

Thanks everybody who created (and contributed to) this project that 
looks a fantastic tool to observe and tinker with vehicles!

Please feel free to share your thoughts on this.

Regards from France,
Ludovic LANGE
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