How to set USB port as RS-485 entrance? How to interpret Growatt solar inverter commands?

[P247]

I have a solar inverter from Growatt (Model: MAX 70 KTL3 LV datasheet in attachment). I’m trying to read data from it using Modbus. For this, I’ve linked it to my laptop using an RS485 cable (with an USB-converter for my laptop’s USB port).

I’ve been having some trouble reading the parameters. I’ve done some troubleshooting and there are two things I need help with:

-Allegedly, I need to explicitly set the USB port I’m entering the USB-connector to as an RS485 port. This should be do-able in device manager. In demonstrations, I see a check box under the ‘port settings’ tab under the window that opens when clicking the COM-port in question. I, however, can’t find such a thing, also not under the ‘driver’ tab.

How should I be doing this?

-I’ve been told solar converters from this brand won’t give off any data if you don’t request it. The producer has given me some documentation with commands (attachement: Growatt Inverter Communication Command), but it’s badly translated from Chinese and I can’t understand them. Is anyone familiar with the commands written in this file and how I should enter them? Is there a specific type of software I need? How do I interpret them anyway?

 

[KlausST]

Hi,

please show the exact part name and vendor of the USB-RS485 converter.
Best: a link to the datasheet.

Also show exactly how you connected it. Sketch.

Klaus

 

[danadakk]

-Allegedly, I need to explicitly set the USB port I’m entering the USB-connector to as an RS485 port. This should be do-able in device manager. In demonstrations, I see a check box under the ‘port settings’ tab under the window that opens when clicking the COM-port in question. I, however, can’t find such a thing, also not under the ‘driver’ tab.

That sure sounds like dongle has a specific driver that has to be used for the USB side....


Regards, Dana.

 

[FvM]

Most USB-to-RS485 cables use standard Windows COM port driver and don't have special RS485 related settings. The cable used in the left screenshot has apparently installed a special driver, but yours doesn't. That's no problem as such.

It's however important that you know how connect the RS485 cable.

You are talking about MODBUS communication, but the inverter is apparently vendor specfic and has nothing to do with MODBUS, neither RTU or ASCII.

 

[P247]

Hi,

please show the exact part name and vendor of the USB-RS485 converter.
Best: a link to the datasheet.

Also show exactly how you connected it. Sketch.

Klaus

Here's where I ordered it https://webshop.cedel.nl/Modbus-con...W6OZAYbf4P9D2e6Vt0_uPfw-WOKxPhm0aAuL7EALw_wcB
Unfortunately the website's not in English and there doesn't seem to be a datasheet on it, nor did one come with its delivery. What you should know is that the chip inside it is called CH340, I did found this datasheet for it: https://pdf1.alldatasheet.com/datasheet-pdf/view/1132602/WCH/CH340.html

Here's a photo of the linkage:

 

[FvM]

Any indications that the converter isn't operating with your inverter? If not, what are you asking specifically?

 

[P247]

Most USB-to-RS485 cables use standard Windows COM port driver and don't have special RS485 related settings. The cable used in the left screenshot has apparently installed a special driver, but yours doesn't. That's no problem as such.

It's however important that you know how connect the RS485 cable.

You are talking about MODBUS communication, but the inverter is apparently vendor specfic and has nothing to do with MODBUS, neither RTU or ASCII.

I contacted Growatt (the producer) and they told me the inverter should in fact be Modbus-accessible through its RS485 connector and they even gave me another PDF containing the parameters that should be found in 2 registers (see attachment to this message, p9 = holding register, p47 = input register).

Any indications that the converter isn't operating with your inverter? If not, what are you asking specifically?

Ehh, according to the manual one icon on the inverter's outside display should light up when a connection to a computer is made. Doesn't happen with my laptop, did happen with a colleague's, who didn't get the RS485 checkbox in his device manager either.

What I'm trying to get is the data from the two registers I mentioned, which you can also find in the manual I attached.