[Ovmsdev] Getting up-to-speed on Ioniq 5 - Newb help on obdii commands

Michael Balzer dexter at expeedo.de
Wed Sep 21 00:56:28 HKT 2022


the obdii command's broadcast feature isn't capable of processing 
multiple responses, maybe that's what happens. It's more meant as a ping 
to see if there are some SAE conforming devices on the bus.

Don't expect to detect specialized devices by a broadcast, only some 
devices acting in the standard SAE/OBDII ID range (7E0-7E7) will listen 
to the broadcast ID. To find ISO-TP devices not conforming to the SAE ID 
range, you need to loop over the probable TX ID range, e.g. 500-7FF 
(make sure there are no process data frames present in that range 
first). Looping over an ID range is currently best done using a script, 
the re scan tool lacks this option.

Most EV do not implement standard SAE OBDII PIDs, so querying the VIN by 
0902 normally doesn't work (see other vehicle modules for some 
examples). Most EV don't even comply to the OBDII standard of giving you 
bitsets of supported PIDs.

But as you see a response, try sending the request to the device the 
response corresponds to (i.e. response ID - 8). The VIN should normally 
be on device 7E0 7E8. It's also totally normal the devices only respond 
while the car is on, awake or charging. Finding out how to wake up a car 
from OBD is one of the hard parts.

Finally, if the vehicle currently loaded doesn't implement a full 
shutdown (happens when switching to another vehicle like NONE), you may 
end up with partially initialized CAN interfaces or other strange 
issues. To make sure the vehicle module doesn't interfere with your 
scans, boot into vehicle NONE.


Am 20.09.22 um 08:26 schrieb Michael Geddes:
> Hi all,
> I have got my OVMS device (no SIM yet, but I'm working on that), and 
> have been connecting and playing round with commands.
> I'm starting to get my head around things. I have being mucking round 
> with SavvyCan and now understand a little the ISO-TP protocol stuff 
> happening on top of the standard can bus now.  SavvyCan seems to like 
> disconnecting from the TCP server, but going via a COM emulator seems 
> to work better (and can be restarted). All very weird, but I can cope 
> with that.
> I'm getting a weird response from the following when it responds (VIN):
> obdii can1 request broadcast 0902
> It contains elements of my actual VIN but not the main number at the 
> end.  I'm wondering if this is an OBDII receive issue?  Does this 
> command work for other people to get the actual VIN? Also it seems to 
> only work in certain circumstances (?when the car is on?).. which is 
> "fun".
> I have also had issues where if I use the "Set Car to NONE" on the RE 
> PID Scanner interface, it seems to stop communications.. and 
> obdiicommand set no longer works - even if I restart the CAN bus. 
> Setting the vehicle back to 'KO' seems to fix things.
> //.ichael Geddes

Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26

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