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Pieter Boomsma avatar image
Pieter Boomsma asked

Device ID over 255 in Modbus

Hello,

Recently i got quite some more MPPT's since there are no optimizers available. Now in my system i see the devices get device instance id's 280 and 281, this means they also get modbus addresses according to that in this case also 280 and 281. Thats unhandy since there are quite a few applications able to address devices with a Unit ID of over 255.


The excel document states there is no remap for ths id's.

Since there are currently quite some of the unit id's not in use i would like to know if there is a way to remap the unit id's or the ttyUSB instance to another one so it matches a different id.

1638522536576.png

Modbus TCP
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6 Answers
tnt369 avatar image
tnt369 answered ·

I solved it by this way:

Change mapping of Unit ID.pdf


change-mapping-of-unit-id.pdf (586.3 KiB)
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Pieter Boomsma avatar image
Pieter Boomsma answered ·

@tnt369 Thanks, that works. I found the page already but wasn't sure if that would go to work. For now your manual works. I however did this with Nano which is available on a Venus device with SSH. This makes it easy to do this trough Putty or in my case the terminal from my home assistant setup.

Anyway, i added the following 2 lines in case anyone ever needs this:

150,280,VE.Direct via USB, Extra port
151,281,VE.Direct via USB, Extra port
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orjuela90 avatar image orjuela90 commented ·
i have a question, what is the user to login since it shows me acces denied to the cerbo gx
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wkirby avatar image wkirby ♦♦ orjuela90 commented ·

https://www.victronenergy.com/live/ccgx:root_access

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tnt369 avatar image
tnt369 answered ·

I use winSCP to login to the device and save the existing file by copy it to my computer. After that i edit the file on the device by adding new lines/entrys.

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simat avatar image
simat answered ·

I can confirm that this still works on Venus 3.00


Changed 226,279,Cerbo GX VE.Direct port 1 (ttyS7)

to 226,280,Cerbo GX VE.Direct port 1 (ttyS7)


in /opt/victronenergy/dbus-modbustcp/unitid2di.csv


For a replacement RS450/100 MPPT.

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alexander-kolb avatar image
alexander-kolb answered ·

In the modbus protocol one might find, that there is 1 byte only for adressing the device ID - i.e. hex "ff" can only handle devices up to 255. Case you enter new lines in the config files with device address greater than 255 - how do you change your modbus command?

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alexander-kolb answered ·
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Related Resources

Modbus TCP Basics