I have a MUST PH1800 Plus inverter (Voltronic clone / look alike).
It has USB, RJ45 and what looks like an RS-232 port.

I know that the USB can be used for PC software and have successfully used it with Solar Assistant. It seems to be a USB to RS485 internal converter.

The RJ45 also has RS485 pins and CAN pins.

The RS232 like port is on the parallel board.

I was wondering: Does the CAN port publish any data from the inverter, or is it used just for reading battery data from a BMS?

Can any data be read from the parallel board's (RS232) port ?

The reason I'm asking, is that I want to use Solar Assistant (via USB) AND connect a small microcontroller (like ESP or Arduino) for some simple automation (driving an external N-G bond relay when inverter is in off-grid mode).

I know that SA supports MQTT, but I really don't want to run another Raspberry Pi just for receiving the MQTT data. I want to use a low-level microcontroller like Arduino for the N-G bond relay, because it's "mission critical" for obvious safety reasons.

I wouldn't trust a Raspberry Pi for critical stuff. Especially not over WiFi.

If SA would allow running a script locally, to drive the relay, that would be nice, but again I would have worries about the robustness.

I have tried to connect two devices, one to the USB and another to the RS485 pins of the RJ45 but it seems that it's basically on the same BUS, so the devices interfere. Only one can communicate with the inverter at a time.

Has anyone tried two devices on two different interfaces of these types of inverters?

Thanks

2 hours ago, meetyg said:

I have a MUST PH1800 Plus inverter (Voltronic clone / look alike).

Must Power started out as a straight Axpert clone maker, but their latest products seem to have diverged somewhat from the Axpert design. For example, I believe that the PH1800 can export to the grid, and has settings for that.

2 hours ago, meetyg said:

It has USB, RJ45 and what looks like an RS-232 port.

On an Axpert, the RJ-45 IS the RS-232 port, if it's on the comms board near the type A USB connector. These two use the same serial port on the DSP, so you can't use them independently.

I don't know what you mean by "looks like an RS-232 port".

2 hours ago, meetyg said:

The RS232 like port is on the parallel board.

On Axperts, the paralleling board doesn't have RS-232, only CAN bus and an analogue connection for current sharing. The ports that look like EGA or VGA ports (three lines of pins, RS-232 only ever has two lines) have the CAN bus and a few other connections. I have a partial schematic trace here. The CAN bus for paralleling can't be used for any sort of monitoring; it's totally dedicated to paralleling.

2 hours ago, meetyg said:

I was wondering: Does the CAN port publish any data from the inverter, or is it used just for reading battery data from a BMS?

There is a CAN bus port on some Axperts, specifically the ones with either the removable display, or the newer ones with the colour display and the LED ring around it. This CAN bus is only used for BMS comms, and then only for certain protocols (NOT Pylontech; Pylontech comms is only via RS-485). These RJ-45 ports combine RS-485 and CAN bus, and are clearly marked as being for BMS. I have no idea if any MUST models have copied this.

Great information, thanks!

I will look into the schematics you posted.

Yes, I meant those VGA looking ports. They are in the parallel board only.

I will post some pictures later on, just for your reference.

I don't think the MUST has any "real" RS232 comm.

My hopes were to get some information from the VGA type connector on the parallel board.

I will try to snoop around that port according to your schematics, maybe I'll find something interesting.

Sadly the N-G bond issue (lack of internal bind/relay) has really got to me.

But I'm trying to do the best with what I have, rather than returning the inverter to China (if they will accept my return anyways).

I meant to add that Axperts come with an RJ-45 to D9 adapter cable for the RS-232 port. Did your Must come with one? 

No, just a USB cable, and a parallel (M to F) D9 cable.