USB-to-RS485 and Power Meter ... can't get it to work

[DickesC]

Hi

I have a UniPi 1.1 and a USB to RS485 Adapter.
With this i would like to meassure values from a SDM120-Modbus power meter.

But i simply can't get it to work.
I tried it in Rexygen, and it was way easier.

In Mervis i don't know where to start.
e.g. where should i put the "connection parameters" (/dev/ttyUSB0)

Any help?

Thanks

[Martin Kudláček]

Hi @dickesc,
I would suggest to take at our Connecting to Modbus slave tutorial. You can select USB1 - USB4 in the configuration of the ModbusRTU channel.

Best regards,
Martin

[DickesC]

Thanks for the Link

So i have tried the following:

• add a channel

Protocol "Modbus"
Link Protocol "Serial"
Port Number "USB Port1"
Baud Rate "9600"
Data Bits "8"
Parity "None"
Stop Bits "One"

• add a device

Device Address "1"

• add a group to the device

Starting Element "30001"
Quantity of Elements "6"

• add a Data Point

Select the right group
Comm Value "BuiltIn"
ST Type "real"
MultiByte Length "4"

• Set Autogen

• Build and deploy

When i debug it i get "Port initialization Failed (status 53)" i the Port Monitor.
In the Variable Browser i get "Communication Error" and a PLC Value of "0".

So, what can i do next?

Thanks

[Martin Kudláček]

Hi @dickesc,
did you connect the converter to the correct USB. This is the USB1:

[DickesC]

Hi

Yes, i have it connected to this port.
And i have tried all the other ports too.

[DickesC]

Hi

In the meantime i got my Neuron M203.
The UniPi was just for testing.

With the Neuron i can "communicate" with the SDM120-Modbus, but i can get no values.

Can someone help me with the configuration for

• Modbus Group Parameters
• Comm. Value Mapped Type
• ST Type
• Data Offset
• MultiByte Lenght

The Modbus register map you can find here:

https://bg-etech.de/download/manual/SDM120C-Modbus-DE.pdf
http://www.eastroneurope.com/media/_system/tech_specs/3914/SDM120 PROTOCOL.pdf

Thanks