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rkapsi avatar image
rkapsi asked

Connecting BMS (500 kbit/s) to VE.Can port?

Is there any functional difference between the "CAN-bus BMS (500 kbit/s)" and the "VE.Can & CAN-bus BMS (250 kbit/s)" profiles asides the Bitrate?


If I had a BMS that it fixed at 500 kbit/s and if I wanted to connect it to Cerbo's VE.Can port using the "VE.Can & CAN-bus BMS (250 kbit/s)" profile then could I do so using a CAN Bridge to simply step down the Bitrate? And if this wouldn't be a problem then is there a way to configure the Cerbo the use 500 kbit/s for the "VE.Can & CAN-bus BMS" profile?

cerbo gxVE.Can
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4 Answers
thanar avatar image
thanar answered ·

You can set the VE.Can port speed to 500kbit/s through Console:

screenshot-2024-02-01-at-112756.png


screenshot-2024-02-01-at-112756.png (107.7 KiB)
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rkapsi avatar image
rkapsi answered ·

For clarification. I can change the speed for the "VE.Can & CAN-bus BMS (250 kbit/s)" profile using the command line?

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Fideri avatar image Fideri commented ·
@rkapsi
My Cerbo has two different ports: a BMS.Can and a VE.Can. According to the manual, the BMS.Can is set to 500kbit/s and VE.Can is set to 250kbit/s but both can be changed as shown by @thanar. I don't know about the command line.

Fideri

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @rkapsi,

There is some nuance to answering this question.

There are hardware differences between the VE.Can and BMS-Can interface ports on Victron GX devices.

The VE.Can ports (250kbps) are able to be configured as BMS-Can ports (500 kbps) via the GX device menu interface.

However the BMS-Can ports (500 kbps) are not able to be configured as VE.Can ports (250 kbps).

Recent hardware revisions of the Cerbo GX include two VE.Can ports and allow the most flexibility.

Previous hardware revisions had one of each.

It may be possible to change the VE.Can port to a BMS-Can port via the command line, but I would expect it is not documented how, I’ve never seen it, so might require some homework (canbus interfaces are common, and Venus is open source), and if you really hit a dead end, try a thread in the modifications section.

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rkapsi avatar image rkapsi commented ·

Thanks. The terminology and history are unfortunately very convoluted which makes it difficult to condense the question without causing a lot of confusion. A graphical expression of my question would look something like this:


69996-screenshot-2024-02-01-at-112756.png


I don't know if @thanar was referring to the command line when he said Console but it appears to work. I first change the CAN-bus profile to "VE.Can & CAN-bus BMS (250 kbit/s)" followed by SSH'ing into the Cerbo GX (in this case the Mk2 model) and changing the port speed from 250 to 500 kbit/s using:


ip link set down vecan0
ip link set vecan0 type can bitrate 500000
ip link set up vecan0


The BMS shows up on the Cerbo and I also see other non-BMS messages on the bus.

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cliff76 avatar image cliff76 rkapsi commented ·
@rkapsi Did your VE.Can devices work after you made the change to 500kbs? If so, this is exactly what i need to try out. I have a BMS connected to one port @ 500Kbs, but I want to add an energy meter that uses VE.Can to the spare VE.Can port. Im not sure if the energy meter will connect on the VE.Can port at 500kbs, though?
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rkapsi avatar image rkapsi cliff76 commented ·

I don't think the energy meter will work unless it can be configured to use 500 kbit/s. There is no auto negotiation and all participants need to be explicitly configured bitrate. In my case I've a BMS that is fixed at 500 kbit/s, I have a Wakespeed that can be configured to use any bitrate and the Cerbo I can force to 500 kbit/s.

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rkapsi avatar image
rkapsi answered ·

To whom it may concern. I've condensed what I want to do into a (hopefully) reliable script that intercepts the GX's own attempt to set the bitrate and overwrites it with my own value. The GX UI will say 250 kbit/s but under the hood it's 500 kbit/s. No changes to GX's own files are necessary and the script survives reboots and firmware upgrades.

Github: https://github.com/rkapsi/wecan

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Related Resources

Cerbo GX product page

GX family product range

Cerbo GX & GX Touch datasheet

Cerbo GX Manual

Venus root access document

Additional resources still need to be added for this topic