[Ovmsdev] Can buses stop after some time

Greg D. gregd2350 at gmail.com
Mon Jul 9 09:49:15 HKT 2018

Hi Tom,

For what it's worth, I'm using an OBDII splitter cable, and Raspberry Pi
3b + PiCAN2 daughter board for capturing traffic with Wireshark.  The
cable lets me snoop on the traffic between the  OVMS and car or HUD,
without interference.



I didn't use the 9-pin connector - didn't find a plug-and-play cable. 
Just wired the CAN+, CAN- and Ground signals into the splitter cable
connector by pushing wires into the socket.  Remember to NOT use the
termination resistor on the PiCan2 board (the default).

Given all the changes to the system, I probably should toss my debugging
hacks and update to the latest, before digging back in.

Taking a deep breath,


Tom Parker wrote:
> On 08/07/18 04:53, Greg D. wrote:
>> Is there a way to compare sent and received data, to see what was
>> lost, for example, were they 3 random single frames, or two in a
>> row?  Might give an idea of the size of the distraction that's
>> causing the overflow.
> This is important, checking for correctness during performance testing
> is often overlooked!
>> Do we have any timing data from Tom's vehicle?  Just wondering what
>> the inter-frame gaps are, and such.  Since it locks up so quickly, a
>> Wireshark trace would be wonderful to pick through, or perhaps even
>> replay.
> https://carrott.org/pcaps/leaf-2016-car-driving.pcap.bz2
> I'm not sure of the time resolution of my can bus hardware (one of
> these https://www.mictronics.de/projects/usb-can-bus/ ), the
> timestamps look quite funky, it seems that they count up in 10uS
> increments and then jump 10ms. So I think maybe it only has 10mS
> resolution. If that is the case they appear to come pretty fast, maybe
> 22 frames per 10ms.
> I haven't tried to play this recording back into the OVMS yet, but it
> is quite long. I didn't have the OVMS plugged in at the same time
> because I can't capture the car bus and feed it into the OVMS's can2
> interface at the same time. Hence I don't know when or if can2 would
> stop working. I could also try recording on the OVMS itself but I
> haven't been able to make the sdcard work on my 3.0 unit, and
> recording there may well influence the problem without capturing it's
> cause.
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