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?

 

[danadak]

-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 you need a specific manufacturer driver for that port .....? For the dongle
USB to 485.


Regards, Dana.

 

[P247]

That sure sounds like you need a specific manufacturer driver for that port .....? For the dongle
USB to 485.


Regards, Dana.

Thank you for your response. A driver was installed once I entered the dongle into my USB port. I also found more drivers for the RS485-USB converter on this website (even though this is not where I ordered it) https://www.tinytronics.nl/shop/nl/...n/serieel/rs-485/usb-naar-rs485-adapter-ch340. Installing any of them didn't fix it.

 

[danadak]

If the driver does not show that config selection in the driver
properties then I think you still do not have the right driver
installed.

Contact the support arm for the dongle and ask for their driver
for the specific dongle model you have.


Regards, Dana.

 

[rjenkinsgb]

I suspect you have a generic USB adapter cable (FTDI chipset), rather than one with the EXAR chipset as in the screenshot you included.

You probably need the correct exar chipset type cable, such as this:

Kalea-Informatique Chipset Exar XR21B1411 USB to RS232 RS422 RS485 Converter 1.8 m Cable Magnetic Anti-Parasite Protection : Amazon.co.uk: Computers & Accessories

Buy

www.amazon.co.uk

 

[P247]

Contact the support arm for the dongle and ask for their driver
for the specific dongle model you have.

Okay I just contacted them and they told me the correct driver should be the one I found online XD

 

[For The Popcorn]

I haven't seen any specific description of the USB converter. There are basically three general possibilities. I'm going to use the CH340 USB–serial chip as an example, but the same comments apply to FTDI, Prolific and other chips.

● USB – UART Adapter

USB --> CH340 --> 3.3 or 5 volt to micro. This type of adapter is used to get a serial connection between a microcontroller and a computer.

● USB – RS232 Adapter

USB --> CH340 --> MAX232 Chip --> RS232 Device

This type of adapter provides a serial connection between an RS232 device and computer. Usually uses DB9 connector, and signal levels are inverted compared to a UART signal and typically are –12v / +12v although these levels vary widely.

● USB – RS422/RS485 Adapter

USB --> CH340 --> RS485 Driver Chip --> RS422/RS485 Device

This type of adapter provides a serial connection between two or more devices using a differential pair of wires for noise immunity. Rather than the low/high signaling levels of RS232, the difference in levels between the two wires in a pair determine if a bit is high or low. It is fundamentally different than RS232 and requires a different driver chip.



The same CH340 chip provides the USB–Serial interface for these three different technologies. It's what follows the CH340 that determines what the communication mode will be. If the adapter doesn't have an RS485 chip, no driver or tick mark in the computer is going to make it work.

 

[P247]

I haven't seen any specific description of the USB converter. There are basically three general possibilities. I'm going to use the CH340 USB–serial chip as an example, but the same comments apply to FTDI, Prolific and other chips.

● USB – UART Adapter

USB --> CH340 --> 3.3 or 5 volt to micro. This type of adapter is used to get a serial connection between a microcontroller and a computer.

● USB – RS232 Adapter

USB --> CH340 --> MAX232 Chip --> RS232 Device

This type of adapter provides a serial connection between an RS232 device and computer. Usually uses DB9 connector, and signal levels are inverted compared to a UART signal and typically are –12v / +12v although these levels vary widely.

● USB – RS422/RS485 Adapter

USB --> CH340 --> RS485 Driver Chip --> RS422/RS485 Device

This type of adapter provides a serial connection between two or more devices using a differential pair of wires for noise immunity. Rather than the low/high signaling levels of RS232, the difference in levels between the two wires in a pair determine if a bit is high or low. It is fundamentally different than RS232 and requires a different driver chip.



The same CH340 chip provides the USB–Serial interface for these three different technologies. It's what follows the CH340 that determines what the communication mode will be. If the adapter doesn't have an RS485 chip, no driver or tick mark in the computer is going to make it work.

Thanks for your reaction. This is the one I'm using https://webshop.cedel.nl/Modbus-converter. The website doesn't have a datasheet, but when I contacted them they did mention that there's a CH341 chip in the converter. I don't know if there's a RS485 driver chip, perhaps it would be useful to find a converter which I'm sure contains that particular chip, such as this one https://www.hobbyelectronica.nl/pro...yWcNrUq2CpyMDVNwhSXUlKW-8X_aN4yQaAkrIEALw_wcB ? It mentions a 'MAX485' chip.

 

[For The Popcorn]

The Modbus converter should work, but the other is cheap enough to try.

The end points on an RS485 network require termination resistors across the wire pair, 120 ohms as I recall. If the documentation doesn't specifically mention an integrated termination resistor for the adapter and solar inverter, try adding one at either end and both ends. They are often just connected across the terminal block.

Oh, and just to be sure.... the A terminal of one end goes to the A terminal of the other end and B to B.