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As all tests were positive and without issues, I've merged the
rework into master.<br>
<br>
I now consider extending the poller to allow to hook into
transmission failures.<br>
<br>
Also, if a TX callback is present in a frame, I don't think we need
the error log entry from the CAN framework. That would eliminate
most CAN error log messages from regular poller "pings".<br>
<br>
Regards,<br>
Michael<br>
<br>
<br>
<div class="moz-cite-prefix">Am 08.01.21 um 18:52 schrieb Michael
Balzer:<br>
</div>
<blockquote type="cite"
cite="mid:500d87f4-b88b-2dd1-0da5-8799d397183a@expeedo.de">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Steve,<br>
<br>
thanks, that's perfect. The failure handling works as designed in
your case.<br>
<br>
Regarding your question: <br>
<blockquote type="cite">
<div>It does prompt me to ask a question that I had - On the i3,
if you do something like send a lock from the key or the
Connected Drive APP then the OBD-II comes alive but goes
asleep again in less than a minute.</div>
<div><br>
</div>
<div>if I have a PID that I poll infrequently - say every 120
seconds. What happens in this case? Would they be seen as
"overdue" when the bus comes alive and polled immediately, or
is it a matter of luck if the 120th tick arrives at a time
when the bus is alive?<br>
</div>
<div><br>
</div>
<div>If the latter I need to poll even things like the VIN every
10 seconds to make sure I get it before the bus goes to sleep
again.</div>
</blockquote>
<br>
With the old handling, the queued frames would have get sent as
soon as the bus got awake again. That's nasty, as the frames may
have been for a specific task (e.g. some protocol part), and
should not be sent to a just woken up car. That could produce any
sort of problem up to queued OBD writes corrupting the car memory.
It was also nasty the driver would then send the whole TX queue at
once, flooding the bus. A vehicle could see that as a malicious
activity and block access.<br>
<br>
The new handling will abort the transmission as soon as the CAN
controller runs into the retransmission limit (128 tries, formally
CAN error-passive mode).<br>
<br>
So you now need to "ping" the car with some simple read or session
state request, and check if a response comes in to determine if
the bus is online. If using the poller, you'll get a respective
Incoming…() callback. If you don't use the poller, you can set the
TX callback pointer on the frame you send. The TX callback is
called with a success indicator, so you can know a frame has been
sent even if you don't get a response from the device.<br>
<br>
Regards,<br>
Michael<br>
<br>
<br>
<div class="moz-cite-prefix">Am 08.01.21 um 09:33 schrieb Steve
Davies:<br>
</div>
<blockquote type="cite"
cite="mid:CABFTEGXQDiknKXzP0fFV++3RVNCmbd=wfP9SnJUShzeS_t1bkQ@mail.gmail.com">
<meta http-equiv="content-type" content="text/html;
charset=UTF-8">
<div dir="ltr">Hi Michael,
<div><br>
</div>
<div>Here's the log from a test on my car with your branch</div>
<div><br>
</div>
<div>I started the car, left it for a while, then shut it down
and waited until the OBD-II first went to "not getting
replies to my requests" and then to "not sending anything at
all".</div>
<div><br>
</div>
<div>Hope its helpful.</div>
<div><br>
</div>
<div><a
href="https://drive.google.com/file/d/1AavD41HCykYrn-BxQXNufu2dT_UVCXYU/view?usp=sharing"
moz-do-not-send="true">https://drive.google.com/file/d/1AavD41HCykYrn-BxQXNufu2dT_UVCXYU/view?usp=sharing</a><br>
</div>
<div><br>
</div>
<div>Steve</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, 8 Jan 2021 at 08:22,
Steve Davies <<a href="mailto:steve@telviva.co.za"
moz-do-not-send="true">steve@telviva.co.za</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi Michael,
<div><br>
</div>
<div>The change looks helpful, thanks. I'll try it during
the course of the day.</div>
<div><br>
</div>
<div>It does prompt me to ask a question that I had - On
the i3, if you do something like send a lock from the
key or the Connected Drive APP then the OBD-II comes
alive but goes asleep again in less than a minute.</div>
<div><br>
</div>
<div>if I have a PID that I poll infrequently - say every
120 seconds. What happens in this case? Would they be
seen as "overdue" when the bus comes alive and polled
immediately, or is it a matter of luck if the 120th tick
arrives at a time when the bus is alive?<br>
</div>
<div><br>
</div>
<div>If the latter I need to poll even things like the VIN
every 10 seconds to make sure I get it before the bus
goes to sleep again.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Steve</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, 7 Jan 2021 at
18:22, Michael Balzer <<a
href="mailto:dexter@expeedo.de" target="_blank"
moz-do-not-send="true">dexter@expeedo.de</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div> Everyone,<br>
<br>
please pull & test the new "can-txfail-fix"
branch. It's up to date and includes the BMW i3 code
already.<br>
<br>
I need to get feedback from users of both can1
(esp32can) & can2/3/4 (mcp2515), as changes had to
be made to both drivers.<br>
<br>
I'll quote from my commit: <br>
<a
href="https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/commit/c94592a11ad2c989e65313d23a8876cf38787d70"
target="_blank" moz-do-not-send="true">https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/commit/c94592a11ad2c989e65313d23a8876cf38787d70</a><br>
<br>
<div
style="box-sizing:border-box;display:block;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe
UI",Helvetica,Arial,sans-serif,"Apple
Color Emoji","Segoe UI
Emoji";font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration-style:initial;text-decoration-color:initial">
<pre style="box-sizing:border-box;font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:13px;margin-top:10px;margin-bottom:0px;max-width:100%;line-height:1.45;white-space:pre-wrap;overflow:visible">Design goals:
- any TX can either fail or succeed, the result state is terminal
- the respective TX callback is called exactly once
- transmissions fail on reaching the error-passive bus state
and on message/bus errors while in error-passive state
- a failed TX will be aborted (no retries after bus recovery),
i.e. will be retried at most 128 times (in error-active phase)
- reduce excessive CAN error logging
- reduce excessive interrupt load with switched-off buses
This results in the application being able to reliably detect a
switched-off vehicle bus by the TX callback's success indicator.
It also results in frames no longer being held in the TX buffer
or added to the TX queue when the bus is switched off. The
application can now rely on getting a clean bus state on every
reconnect, without any queued old frames to be sent automatically.
Secondary benefit from aborting the transmission is, the module
doesn't need to handle the load from the continuously triggered
CAN error interrupts by retransmission attempts in error-passive
state.</pre>
</div>
<br>
Reason for this was a) Steve's question on aborting
transmissions / flushing the queue and b) my new car
now also switching off the bus, with the annoying
effect of a frozen can1 every 2-3 days, needing to
reboot the module. I'm not sure yet if the freeze
issue is solved, but I haven't had it since running
these changes on my module.<br>
<br>
The other issue of the transceivers resending frames
queued long ago may have caused all sorts of strange
& unrepeatable issues. I remember the VW crew
having problems that fell into this category.<br>
<br>
I've verified the new MCP2515 implementation only on
my workbench (with an Arduino as the CAN tester), so
real life tests are necessary.<br>
<br>
Thanks,<br>
Michael<br>
<br>
<pre cols="72">--
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26</pre>
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Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26</pre>
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Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26</pre>
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