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Hi Mark,<br>
<br>
Of course. I'm under no illusion that the obd2ecu feature would be
a high-volume product. I'm just concerned about how Tesla, in
particular, or any manufacturer in general, will react to a product
that interacts in a demonstrated negative way with the vehicle's
operation. We already have Tesla telling their service centers that
OVMS is potentially the cause of my 1144 / 1146 alerts, for
example. If they start seeing this sort of behavior (VMS crashing),
the fallout could be severe, where they could refuse all service on
the vehicle. In my opinion, OVMS must provide a strict firewall
between the car and anything we attach to it, and by feeding the
other two CAN buses through from one connector to the other, we've
removed all protection. The result was spectacularly not good.<br>
<br>
I guess "snip snip" will probably work, if it's well documented. If
the answer is documentation, how do we get the word out? Two
options; kill CAN 3 to the car and lose the future ESS metrics, but
leave the OBDII pigtail as-is; probably the 90% solution. Or kill
CAN2 to the car and make a custom OBDII pigtail. But I would
strongly urge anyone using the obd2ecu feature to fully isolate the
attached device from the car's buses, even if they seem to be
getting along.<br>
<br>
I'm Ok on the speed parameter. I wasn't seeing any speed
negotiation in my testing, but I also have a fairly small sample of
devices here. It will take me some time to re-create the build
environment here, as I haven't been keeping it up to date. Right
now I'm trying to get my car back on the road (failed PEM Fan
connector). Parts for the next steps arrive today. <br>
<br>
Greg<br>
<br>
<br>
<div class="moz-cite-prefix">Mark Webb-Johnson wrote:<br>
</div>
<blockquote type="cite"
cite="mid:65F496DD-232F-4AF9-BF02-C83EE568A503@webb-johnson.net">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Greg,
<div class=""><br class="">
</div>
<div class="">
<blockquote type="cite" class="">
<div text="#000000" bgcolor="#FFFFFF" class="">How do we make
this "Layman safe" out-of-the-box</div>
</blockquote>
<br class="">
</div>
<div class="">The issue is one off quantity. There simply aren’t
enough users of the HUD system to make it economically feasible
to have custom cables for everyone (and to cripple the 99.9% of
users who don’t use the functionality by removing support for
one of their CAN buses). The manufacturers I deal with in china
have a MOQ of about 100 for custom hard-wired cables. We have
sold about 20 HUD cables in the past year or two (leaving the
project with 80 unused in stock). It would be worse if we had to
make two or three different variants of this.</div>
<div class=""><br class="">
</div>
<div class="">Sorry to sound negative, but given the limitations
and quantities involved, I think the reality is that the HUD
system is always going to have to be very custom (last least on
cars with more than two CAN buses).</div>
<div class=""><br class="">
</div>
<div class="">That said, the Tesla cars are the only ones at
present that use CAN3, so the solution should be purely to
document exactly what is required for those cars. Personally, I
think it easiest to cut CAN3 from the OVT1/OVT2 cable, use the
standard HUD cable, and live with the limitations. Snip Snip. If
the HUD supports 125Kbps, the alternative is to set obd2ecu to
that, but I really don’t like the idea of running OBDII traffic
on buses not intended for that.</div>
<div class=""><br class="">
</div>
<div class="">
<blockquote type="cite" class="">
<div text="#000000" bgcolor="#FFFFFF" class="">Should I deny
allowing obd2ecu to be configured on CAN1?</div>
</blockquote>
<br class="">
</div>
<div class="">I don’t see any advantage to crippling that
functionality. There may be cases where that is the best
approach.</div>
<div class=""><br class="">
</div>
<div class="">
<blockquote type="cite" class="">
<div text="#000000" bgcolor="#FFFFFF" class="">The obd2ecu
task is fixed at 500kbps because that's what all of the
HUD-type devices seem to use. Adding a rate parameter
should be easy, but I don't see it as solving anything.</div>
</blockquote>
</div>
<div class=""><br class="">
</div>
<div class="">Standard OBDII devices should negotiate speed. I
know the HUDs I have try 500Kbps and if that doesn’t work they
try 250Kbps, etc. Same for OBDII dongles based on ELM327, etc.</div>
<div class=""><br class="">
</div>
<div class="">The reason I suggested adding the rate parameter is
it gives us some flexibility, and takes nothing away (assuming
it defaults to 500Kbps).</div>
<div class=""><br class="">
</div>
<div class="">This article explains this quite well: <a
href="https://copperhilltech.com/blog/how-can-bus-automatic-baudrate-detection-works-and-what-to-consider-when-connecting-to-a-network/"
class="" moz-do-not-send="true">https://copperhilltech.com/blog/how-can-bus-automatic-baudrate-detection-works-and-what-to-consider-when-connecting-to-a-network/</a></div>
<div class=""><br class="">
</div>
<div class="">See page #25 on this ELM327 spec for their approach
of auto-baud rate detection: <a
href="https://cdn.sparkfun.com/assets/learn_tutorials/8/3/ELM327DS.pdf"
class="" moz-do-not-send="true">https://cdn.sparkfun.com/assets/learn_tutorials/8/3/ELM327DS.pdf</a></div>
<div class=""><br class="">
</div>
<div class="">
<blockquote type="cite" class="">
<div text="#000000" bgcolor="#FFFFFF" class=""> First, why did
starting obd2ecu on CAN3 cause the observed behavior?</div>
</blockquote>
<div class=""><br class="">
</div>
Because the CAN3 in the car is 125Kbps, and the obd2ecu task
configured CAN3 to 500Kbps in active mode. That messed up the
traffic on the car’s CAN bus.</div>
<div class=""><br class="">
</div>
<div class="">
<blockquote type="cite" class="">
<div text="#000000" bgcolor="#FFFFFF" class="">The obd2ecu
task is silent unless and until it receives a valid polling
frame from the device, which should be impossible given the
speed mismatch. How can changing the bit rate on one CAN
device affect the rest of the bus, if that device is
otherwise silent?</div>
</blockquote>
<div class=""><br class="">
</div>
Not quite. The obd2ecu task initialises the bus in ACTIVE mode.
That is not silent. The CAN hardware will, in that mode,
actively participate in bus communications and acknowledge
traffic. LISTEN mode would not be an issue (it would just see
garbage can frames), but you can’t transmit in that mode.</div>
<div class=""><br class="">
</div>
<div class="">
<blockquote type="cite" class="">
<div text="#000000" bgcolor="#FFFFFF" class="">Second, the OP
in the TMC thread stated that they were using a pre-OVT1
cable. If so, CAN 2 & 3 shouldn't have been connected</div>
</blockquote>
<div class=""><br class="">
</div>
Based on the symptoms listed, and solution he gave, his cable
MUST have all three buses connected. Either the OVT1 label was
not not visible, or this cable was prior to us adding those
labels.</div>
<div class=""><br class="">
</div>
<div class="">Regards, Mark.<br class="">
<div><br class="">
<blockquote type="cite" class="">
<div class="">On 4 Aug 2020, at 10:43 AM, Greg D. <<a
href="mailto:gregd2350@gmail.com" class=""
moz-do-not-send="true">gregd2350@gmail.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8" class="">
<div text="#000000" bgcolor="#FFFFFF" class=""> Thanks,
Mark, for posting the update. <br class="">
<br class="">
However, the point is that someone buying a new OVMS and
Roadster OVT1 cable cannot use the obd2ecu feature of
the module without performing some sort of hardware
modification, and this potentially to a molded / sealed
cable. While this isn't a mass-market device, we really
should make the out-of-the-box experience one of not
killing one's car. <br class="">
<br class="">
How do we make this "Layman safe" out-of-the-box, and
configurable for all supported cars without the use of a
soldering iron or wire snips? Is there a table of what
CAN busses are used for each of the supported vehicles?<br
class="">
<br class="">
For the Roadster, at least, it would seem that we need
to change the OVMS to OBDII pigtail to use CAN2, as well
as disconnecting CAN2 from the OVT1 cable. CAN2 is the
only one left with out planned functionality, right?
The new cables would need a label on the OBDII cable
indicating clearly what it needs to be paired with and
what CAN bus it be used for. Alternatively,. would it
be possible to add a jumper block somewhere, so that a
safe pre-install configuration can be done?<br class="">
<br class="">
Should I deny allowing obd2ecu to be configured on
CAN1? Are there any cars or applications where this
would be valid?<br class="">
<br class="">
The obd2ecu task is fixed at 500kbps because that's what
all of the HUD-type devices seem to use. Adding a rate
parameter should be easy, but I don't see it as solving
anything. From the devices I tested, there is no
"negotiation" on CAN bus rate; or much of anything else
for that matter. They just turn on and start talking.
The only flexibility that I observed was whether they
use base or extended frame formats, and I support both
dynamically. Or, are they also sensitive
(self-configuring) to the bus speed, and if so, how is
that done? I suppose matching the 125k speed on CAN3
might work, but I'd really (REALLY) not want to put some
random 3rd party active polling device on my car's ESS
bus. The two worlds need to be firewalled from each
other, and that's the job of OVMS in this case.<br
class="">
<br class="">
All this said, there are still two puzzles in my mind.
First, why did starting obd2ecu on CAN3 cause the
observed behavior? The obd2ecu task is silent unless
and until it receives a valid polling frame from the
device, which should be impossible given the speed
mismatch. How can changing the bit rate on one CAN
device affect the rest of the bus, if that device is
otherwise silent?<br class="">
<br class="">
Second, the OP in the TMC thread stated that they were
using a pre-OVT1 cable. If so, CAN 2 & 3 shouldn't
have been connected, so there should have not been any
possible interaction with either bus in the car.
Something is not adding up here... Or, did some prior
version of the cable also connect to all three?<br
class="">
<br class="">
Greg<br class="">
<br class="">
<br class="">
<div class="moz-cite-prefix">Mark Webb-Johnson wrote:<br
class="">
</div>
<blockquote type="cite"
cite="mid:7B172510-6D65-4111-B9A5-4138C2233163@webb-johnson.net"
class="">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8" class="">
Greg,
<div class=""><br class="">
</div>
<div class="">I updated the TMC thread as follows:</div>
<div class=""><br class="">
</div>
<blockquote style="margin: 0 0 0 40px; border: none;
padding: 0px;" class="">
<div class=""><span style="color: rgb(2, 2, 2);
font-family: Roboto, sans-serif;
font-variant-ligatures: normal; orphans: 2;
widows: 2; background-color: rgb(254, 254,
254);" class="">Here are the Tesla Roadster CAN
bus details:</span><br style="color: rgb(2, 2,
2); font-family: Roboto, sans-serif;
font-variant-ligatures: normal; orphans: 2;
widows: 2; background-color: rgb(254, 254,
254);" class="">
<ul style="margin: 1em 0px 1em 3em; padding: 0px;
color: rgb(2, 2, 2); font-family: Roboto,
sans-serif; font-variant-ligatures: normal;
orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">
<li style="margin: 0px; padding: 0px;
list-style: outside disc;" class="">Instrumentation:
OVMS CAN1 (on OVT1): 1MHz, on DIAG pins 6/1.
Contains VDS, TPMS, Instrumentation Display.</li>
<li style="margin: 0px; padding: 0px;
list-style: outside disc;" class="">Powertrain:
OVMS CAN2 (on OVT1): 500Kbps, on DIAG pins
7/2. Contains PEM, Switchpack, etc.</li>
<li style="margin: 0px; padding: 0px;
list-style: outside disc;" class="">ESS: OVMS
CAN3 (on OVT1): 125Kbps, on DIAG pins 11/4.
Contains ESS and HVAC.</li>
</ul>
<span style="color: rgb(2, 2, 2); font-family:
Roboto, sans-serif; font-variant-ligatures:
normal; orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">The problem you
had is the cable you have between OVMS and the
car wires all three CAN buses. Then when you
start up the obd2ecu on CAN3 at 500kbps that
conflicts with the vehicle's own ESS CAN bus at
125Kbps you are running this on top of. You mess
up the vehicle comms between the VMS, HVAC, and
ESS. It would make no difference if the HUD
cable was plugged in, or not.</span><br
style="color: rgb(2, 2, 2); font-family: Roboto,
sans-serif; font-variant-ligatures: normal;
orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">
<br style="color: rgb(2, 2, 2); font-family:
Roboto, sans-serif; font-variant-ligatures:
normal; orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">
<span style="color: rgb(2, 2, 2); font-family:
Roboto, sans-serif; font-variant-ligatures:
normal; orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">Switching to CAN2
solved the problem because that is the
powertrain CAN bus also at 500Kbps. However,
this is still possibly dangerous, because the
message IDs on the bus may conflict. But
probably ok.</span><br style="color: rgb(2, 2,
2); font-family: Roboto, sans-serif;
font-variant-ligatures: normal; orphans: 2;
widows: 2; background-color: rgb(254, 254,
254);" class="">
<br style="color: rgb(2, 2, 2); font-family:
Roboto, sans-serif; font-variant-ligatures:
normal; orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">
<span style="color: rgb(2, 2, 2); font-family:
Roboto, sans-serif; font-variant-ligatures:
normal; orphans: 2; widows: 2; background-color:
rgb(254, 254, 254);" class="">Given the
limitations, and work we are doing with OVMS, it
is probably best to keep CAN1 and CAN3 for
OVMS-car comms (as those are the two most useful
CAN buses and I plan to release some
functionality on CAN3 ESS bus to show battery
brick voltages and temperatures). If you are
concerned with possible ID conflict, you can
disconnect CAN2 at the DIAG connector (pins #4
and #11) to make sure you don't conflict.</span></div>
</blockquote>
<div class="">
<div class=""><br class="">
</div>
<div class="">This is always going to be vehicle
specific, and probably best addressed by adding
Tesla Roadster specific documentation. It would be
useful to be able to confiture the baud rate of
the bus in the obd2ecu code (but we are limited by
what baud rates the HUDs will support during their
negotiation).</div>
<div class=""><br class="">
</div>
<div class="">Regards, Mark.</div>
<div class=""><br class="">
<blockquote type="cite" class="">
<div class="">On 4 Aug 2020, at 1:29 AM, Greg D.
<<a href="mailto:gregd2350@gmail.com"
class="" moz-do-not-send="true">gregd2350@gmail.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="">Hi Mark,<br class="">
<br class="">
So, following the "OVMS issue: obdii on can3
crashes VMS" thread on TMC<br class="">
led me to an "oops!", I think... Did I miss
something?<br class="">
<br class="">
With the updated OVMS cable to the Diag port
on the Roadster, the report<br class="">
is that all 3 CAN busses are connected to
the car. If so, doesn't that<br class="">
make the obd2ecu process impossible to run,
since there's no CAN bus<br class="">
available on the 26 pin port to connect a
HUD to? And, if one were to<br class="">
hook up a HUD to the 26 pin port, wouldn't
its polls be sent on (at 500<br class="">
kb/s) through the OVMS wiring to the car,
confusing the car?<br class="">
<br class="">
Is the older (single CAN bus) cable still
available? That, I would<br class="">
think, would fix the problem. I have the
original cable, so haven't<br class="">
noticed anything wrong. The OP on that
thread also claimed the original<br class="">
cable, which doesn't make sense.<br class="">
<br class="">
Where is the Oops?<br class="">
<br class="">
Greg<br class="">
<br class="">
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