Posted by: @cathoderay

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@majordennisbloodnok - cripes, it sounds complicated!

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Not really. In effect I've just used my home network to extend the wire. If I had a network cable coming out of the back of my PC into the WaveShare unit and another cable from the WaveShare unit into the RS485 port of the inverter it would be logically speaking exactly the same setup. I know I can communicate with the WaveShare unit so everything that's seeming complicated is already proven working.

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Posted by: @cathoderay

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The key thing is something in software has to do what I have described in the last paragraph, something has to initiate the connection and make the requests. I wonder if that is what is missing on your setup at the moment? 

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I know what you mean, but I don't believe that's the case although self-evidently I'm not in a position to be definite. The Solax integration has to be configured software-wise and that means giving it the IP address of the WaveShare unit, telling it what kind of modbus to use (TCP, RTU over TCP or ASCII over TCP) and what TCP port to use. As a result of that it then does exactly what you're describing and attempting to read the device on the other side. When I do that my logs show several error messages most of which are talking about a failure to read the firmware from addres 0x9. To me this suggests that either the RS485 port on the inverter is not configured correctly, that I've told Solax to use the wrong device address (default is 1 but I've also tried 4) or that I've got the wrong wires connected to the RS485B and -A terminals of the WaveShare unit. The last of these seems to me the most likely, but without a definitive document I'm rather floundering in the dark. Some documents for other Growatt units have suggested wires 1 and 2, some 1 and 5 and some 4 and 5, all with the caveat that if that suggestion doesn't work then switch them round the other way. Ho, hum.

And this is where my investigative process of elimination stalls. I can't test the inverter's port is configured correctly if I don't know I've got it wired up right and I can't test the wiring combinations if I don't know the inverter's port is configured correctly. A little bit of Growatt documentation would go a long way around about now.

@majordennisbloodnok - my hunch is that it is the device address. This can be a gotcha - you can't ask it what it's device address is without knowing its device address! Maybe see if somewhere that (default) address is given? Another scenario: I think I had a situation where two devices both had the same default address, say 1, and to get both to work I had to turn off one (its device ID would remain 1), and then set the device ID on the other device to 2 ('set device 1 ID to 2'), then turn on device 1 again...

Posted by: @cathoderay

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@majordennisbloodnok - my hunch is that it is the device address. This can be a gotcha - you can't ask it what it's device address is without knowing its device address! Maybe see if somewhere that (default) address is given? Another scenario: I think I had a situation where two devices both had the same default address, say 1, and to get both to work I had to turn off one (its device ID would remain 1), and then set the device ID on the other device to 2 ('set device 1 ID to 2'), then turn on device 1 again...

Well worth a try; after all, I only have one device the WaveShare box can talk to so it's not a multi-device setup per se. I'll try and see what I find.

Have you actually got a copy of the Growatt Modbus RTU documentation @majordennisbloodnok ?

If not, then there are several online, such as this one on Github.

Growatt doesn't obey the internationally accepted Modbus standard, but it's a close approximation derived from it.

Note that if you've only got one device connected to an RS485 port on your WaveShare converter, then you can send out a command with the ID as 0, which is 'broadcast'.
What you receive as a reply might not make sense at first, but it does at least confirm you've established communication.

Nope, still no joy. I'll try everything again with the other two pinouts I'm aware have met with success for some others but after that I think I'm going to need some help confirming which wires Growatt are using for RS485 on this particular inverter.

So you need to contact their UK customer support office:

Posted by: @transparent

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Have you actually got a copy of the Growatt Modbus RTU documentation @majordennisbloodnok ?

If not, then there are several online, such as this one on Github.

Growatt doesn't obey the internationally accepted Modbus standard, but it's a close approximation derived from it.

Note that if you've only got one device connected to an RS485 port on your WaveShare converter, then you can send out a command with the ID as 0, which is 'broadcast'.
What you receive as a reply might not make sense at first, but it does at least confirm you've established communication.

That could be very useful to know; thanks. Yes, I've got the documentation you mentioned but to be frank I haven't looked too closely at it so far given I expected it to be irrelevant until I had a successful physical connection. More fool me.

Posted by: @majordennisbloodnok

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Posted by: @transparent

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Have you actually got a copy of the Growatt Modbus RTU documentation @majordennisbloodnok ?

If not, then there are several online, such as this one on Github.

Growatt doesn't obey the internationally accepted Modbus standard, but it's a close approximation derived from it.

Note that if you've only got one device connected to an RS485 port on your WaveShare converter, then you can send out a command with the ID as 0, which is 'broadcast'.
What you receive as a reply might not make sense at first, but it does at least confirm you've established communication.

That could be very useful to know; thanks. Yes, I've got the documentation you mentioned but to be frank I haven't looked too closely at it so far given I expected it to be irrelevant until I had a successful physical connection. More fool me.

 

As I have often told young Engineers, "If all else fails, read the instructions".

Posted by: @derek-m

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Posted by: @majordennisbloodnok

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Posted by: @transparent

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Have you actually got a copy of the Growatt Modbus RTU documentation @majordennisbloodnok ?

If not, then there are several online, such as this one on Github.

Growatt doesn't obey the internationally accepted Modbus standard, but it's a close approximation derived from it.

Note that if you've only got one device connected to an RS485 port on your WaveShare converter, then you can send out a command with the ID as 0, which is 'broadcast'.
What you receive as a reply might not make sense at first, but it does at least confirm you've established communication.

That could be very useful to know; thanks. Yes, I've got the documentation you mentioned but to be frank I haven't looked too closely at it so far given I expected it to be irrelevant until I had a successful physical connection. More fool me.

 

As I have often told young Engineers, "If all else fails, read the instructions". 

I wish I could claim to be young. Or, for that matter, an engineer. Failed on both counts.

And finally!

Houston, we have lift-off; thanks to everyone who gave of their time to help. For reference, the pinout was wires 4 and 5 with 4 being wired into RS485B and 5 into RS485A. Nonetheless, I've decided to start a new thread shortly detailing my wider setup (and related decisions to get to that point) as something of a parallel to @cathoderay's "beginner's guide" thread but with a slightly different emphasis.

Posted by: @majordennisbloodnok

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Houston, we have lift-off

Great, you must be very pleased! I'm also sure others will welcome a separate thread with details of your wider setup, and a slightly different emphasis can only improve the totality of information available here on the forum.

As promised, here's the separate thread. Beware it's more of a blog article than a thread but if it helps anyone then great.