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Playback Won't Shutup!

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1 year 1 month ago #261 by NiallDarwin
Playback Won't Shutup! was created by NiallDarwin
Hi there,
For validation that we were getting a CAN signal at decent strength and timing we hooked up our Arduino Due with EVTVCAN Shield to an oscilloscope. We tried to playback a CAN capture once only. We got CAN data (or something that looked a lot like it ;) ) but it was never ending.



I asked the world of YouTube why and the responses were that the CAN controller is waiting for an ACK. This doesn't sound like the behaviour I would expect. I expect playback to simply play the recording and stop. Has anyone here got any input or suggestions about what we're doing wrong or missing?

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11 months 3 weeks ago #267 by collink
Replied by collink on topic Playback Won't Shutup!
The CAN hardware does tend to default to "send until ACK" so if nothing is setting the ACK bit it will continue to send forever. On a populated CAN bus this is usually OK as there won't be too many resending attempts before the message successfully transfers and is ACK'd. But, it is not always idea. It is possible to put the hardware into "send once and give up" mode. This is usually what a car ECU will do so that a failure in the bus doesn't immediately saturate the bus with re-attempts. I think I ought to add support to SavvyCAN to set the desired transfer mode at the hardware level. Some hardware can also do three attempts and give up. The ESP32 can do this I think. The MCP2517FD can do it for sure. That's the ideal setting for most things. If it fails once it might be an arbitration failure. If it fails to send three times in a row it's probably a bus misconfiguration and it might as well give up.
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3 months 3 weeks ago #306 by NiallDarwin
Replied by NiallDarwin on topic Playback Won't Shutup!
Hi Collin,
Have you progressed this? Thanks :)

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