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canbus logging dropping logs?



Have the ovms v3 and wanted to capture canbus logs for my I-Miev to hopefully find ways to control the car remotely -- I know it's not been done, but going to try :)

When doing a full can bus log, such as

can log start vfs crtd /sd/canLog.crtd 

I see very high amount of discards (50+%). Ofcourse when I filter to a specific pid I do not get discards. Since I don't know which pids I am looking for, I need them all tho :) 

Performance tweaks:

  • If I set vehicle module to none, I no longer see any can bus traffic. Even tho can list shows can 1 active. 
  • Increasing the queue to 200 makes no noticeable improvement.
  • Increasing the freq of the sd card causes it to just in general have write issues, I normally keep it at 16k. 


Before buying a dedicated can bus logger (CLX2000 or equiv) or a new SD card, thought i'd ask here. Is it possible to get 100% success on can logging of all pids? For the purpose of reverse engineering, or is that use case better to buy a dedicated unit? Is the OVMS better suited when you can filter specific pids? 



(On a side note; unsure if the cause. But after trying to do can bus logging with vehicle module none (key ready), I eventually noticed the dashboard was very funky -- empty fuel gauge, range, etc. Anti skid, traction control disabled, etc. Disconnecting OBD and restarting the car with removing the ckey caused the SoH to go from 62% to 92%, and range from 75km to 115km and go into ready state. Not sure how or what, but seemingly I triggerd some sort of reset. Unfortunately a couple on/off with keys and the SoH returned to 62% :( Not sure if changing to Vehicle Module None triggered this or something else I was doing. )



markwj's picture
Sounds like you are exceeding

Sounds like you are exceeding the capability of the SD CARD.

I normally log over wifi to a laptop. That is relatively simple to do (especially with linux/osx workstation).

Thank. I went the way of

Thank. I went the way of using canusb, and ultimately dedicated sniffers from CSS. 


I did the network streaming to savvy can which definitely worked, but since i'm trying to do reverse engineering I was nervous whether I could trust the discard stats on ovms console -- given the network was UDP if I am not mistaken. SD Card felt more confident in knowing if/how much was lost. 

Decided ulitmately better to use a dedicated device while reverse engineering to not miss anything as it's confusing enough without having to doubt if you missed a PID in the capture :) 


Now to just find something interesting so I can contribute to ovms..

markwj's picture
The OVMS logging is over TCP

The OVMS logging is over TCP/IP, and there are counts (show log status) of discarded packets, etc.

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