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

P247

New Member
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.

RS485 COM-port.png



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?

Growatt inverter commands.png
 

Attachments

  • Growatt Inverter Communication Command.pdf
    197.5 KB · Views: 39
  • Datasheet_Growatt_Max_50AFCI_ENG (003) (Solar omvormer).pdf
    1.2 MB · Views: 39

danadak

Active Member
-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

New Member

danadak

Active Member
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.
 

For The Popcorn

Active Member
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

New Member
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

Active Member
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.
 

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