Multiplus 2 with two RS485 connections

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daba asked Feb 18, '22

Multiplus 2 with two RS485 connections

Hello, I have a multiplus with a USB Hub, with 2 USB to RS485 cables, one for the EM23 and the second for the ET112. From time to time the communication with the ET112 fails.

For the EM24 I use the original victron 1.8m cable.

For the ET112 a use a USB to TTL adapter fom FTDI and a TTL to 868MHz radio and on the ET112 side a RS485 to 868MHz converter, the radio device is configured for 9600 baud 8N1 fix.

This setu up works but from time to time the communication fails, I my question is:

- can a USB Hub without extra supply be used e.g. can the multiplus feed two loads with 120mA each.

- does the multiplus change the baudrate of the communication from other than the default 9k6 for ?

Thanks.

Multiplus-II Venus OS VictronConnect

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Answer 1 · 2022-02-18T07:22:15Z

wkirby answered · Feb 18, 2022 at 07:22 AM

You can use a powered USB hub. Although, the MultiPlus should be able to provide 240mA total, but maybe a powered hub would help.

As for the communications dropout, there are quite a few different parts to make up the link to the ET112, so it could be USB or it could be the radio link or maybe there is another external factor causing the problem. Maybe radio interference?

The MultiPlus would not change the baud settings, this would be useless, they will remain fixed.

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Answer 2 · 2022-02-18T09:42:01Z

Warwick Bruce Chapman answered · Feb 18, 2022 at 09:42 AM

I assume this is a MultiPlus-II GX?

What USB hub is being used and how often is the problem being experienced?

We had have very hard time with MP2-GX and USB hubs but we're slowly getting it resolved without yet working out exactly why. We're hoping - in collaboration with the team at Victron - to work out why.

We've tested about 6 different kinds of hubs, both powered and unpowered.

In the meantime, these are stable for us:

https://www.techinn.com/en/digitus-slim-spider-usb-hub/137831753/p - Unpowered

https://za.rs-online.com/web/p/usb-hubs/1385535/ - Powered

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daba commented · Feb 18, 2022 at 09:47 AM

Hi Warwick, thanks a lot for your feedback. I am not sure but the EM26 attached to the USB Hub works flawless. I am using an older noname unpowered USB-Hub. But will also check with self powered HUB.

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Warwick Bruce Chapman daba commented · Feb 18, 2022 at 10:52 AM

If it is not a USB hub issue and it is not broken, don't fix it :P

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Answer 3 · 2022-02-18T09:42:05Z

daba answered · Feb 18, 2022 at 09:42 AM

Hi wkirby, thanks a lot fo feedback. Is there any sugested distance between radio module's antenna and Multiplus2, by the way I will change coax cable to increase distance between inverter and antenna.

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Answer 4 · 2022-02-20T15:55:09Z

daba answered · Feb 20, 2022 at 03:55 PM

Hello, one update from my installation.

Today I used teh Carlo Gavazzi Software with a laptop, I could get a link to the ET112., data was Tx an Rx all the time, the USB Hub and the position of the radio module was unchanged.

After plugging back to Multiplus 2 GX it failed to connect to ET112 (which can be seen at the LED of the radio module, which indicates *only Tx* but no Rx)

So I think this is not the radio module itself, also it isn't the USB Hub either EMI coming from the Multiplus into the radio module via USB cable or the firmware in the Multiplus.

I moved the radio module during plugged to Laptop direct on top of the Multiplus and the communication link was still working. So it seems not to be direct radiation from the Multiplus itself.

Any Idea what kind of test could I do to find out the root source? May be adding some ferrites to the USB line?

I have no Idea :-(

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Answer 5 · 2022-02-22T14:42:44Z

daba answered · Feb 22, 2022 at 02:42 PM

Update:

the problem was related to the ET112 address = 1, which also was the address of the EM24. After changing the adress to = 2 it took some time and it worked.

So I learned one thing:

address missmatch does not lead to a immediate lack of data, it can happed that the system seem to be working properly even after reset or rescan for system somponents. Be carefully with addresses :-D

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