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This seems to do what you need: https://www.advantech.com/products/gf-5vtd/adam-4024/mod_5e18f39b-38ef-4033-98f9-1ede917139ee

I think you might have this backwards. Reading a register is an action that only a master can perform. Also, only a slave has a slave address (unit id). Are you perhaps using Simply Modbus Master? Did you disconnect the display to determine if the display or the heat pump is the master on the...

It seems you picked a fairly complicated system as your first foray into Modbus. It sounds like you have 3 Modbus devices in your system: the heat pump itself, the display, and the WiFi gateway. One of these devices must be the master and the other two are the slaves. I recommend first...

I interpret "Slave address: parameter:H37" as the Modbus slave address is configured by changing parameter "H37". Does the heat pump have a display/menu that allows you to configure parameters? If the heat pump does indeed communicate Modbus, then your theory that the WiFi gateway is the master...

Just to again clarify, as I explained in post #44, whether termination is necessary does NOT depend on how many slave devices are on the Modbus network. It depends on the baud rate and total length of the cabling used, as I've listed in post #33. Please follow my suggestion from post #34: Here...

Please review all of the suggestions given in this thread. There is a good chance it already answers any communication issue you're having with this equipment. If you're still having issues, please explain exactly what you've tried, the results, any error messages, and the exact issue you're having.

No, Modbus Plus is an entirely different protocol from Modbus RTU. The Siemens HMI does not support Modbus Plus. The best solution is to use a RS-232 to RS-485 converter.

According to the Modicon Quantum PLC 140CPU43412A datasheet (https://www.se.com/us/en/product/download-pdf/140CPU43412A), it has 2 Modbus (RS-232) ports and 1 Modbus Plus port. The Proface GP2500 HMI's "HOST-I/F" serial interface supports both RS-232 and RS-422 and its "SUB-SIO" serial...

The Air2O main control board has a LCD screen and keys to navigate the menu system. This would seem like the expected location to set the Modbus slave ID. Is there a parameter on the LCD screen for the Modbus slave ID?

The 5th column in your images tells you the data type. For all of the registers you show, the data type is "int32". Typically "int32" means signed 32-bit integer and "uint32" means unsigned 32-bit integer. There should be a section in the device's manual that explains each data type.

Thanks for coming back and posting an update, it's greatly appreciated. This will surely help others in the future having the same issue.

The SunSpec Modbus is just at the application level, defining what data is in certain registers. The devices still use standard Modbus for communication, so any Modbus master can communicate to them. The benefit of SunSpec Modbus is for interoperability between different manufacturers and so...

I think the Decimals column just means how many places after the decimal you want to see in your display, HMI, etc. This is a preference of how you want to see the value. It is completely up to you what you set this field to. Using Peter's example, if the "Voltage L1-N" has a value of 220.543...

OK, sorry, I missed a very obvious solution. You can use a 2-port Modbus RTU gateway on just one of the Modbus pump monitor devices and use it to effectively change the device's slave address. Essentially, you would configure one port as a Modbus Master (to target address 170) and the other as...

I believe Red Lion's "Modbus Gateway" driver in Crimson may allow you to create multiple slave addresses (i.e. virtual nodes) on a single serial port. Some of their Data Station products do have 3 serial ports, but not all 3 ports are RS-485 (depending on the model, 1 or 2 of the ports are...

Who is the manufacturer and what is the model number of the Modbus pump monitor? Unfortunately, some manufacturers (at least their sales/support personnel) seem to be misinformed or simply do not know the technical details regarding Modbus communication of their own product (as most of the time...

There are multiple ways that vendors document Modbus registers. The register "reference" designation (i.e. the 4X/40000, 3X/30000, 1X/10000, 0x/00000) may or may not be included. In addition, there is also 1-based addressing and 0-based addressing. When the reference designation is used, 1-based...

I don't believe there is any maximum timing requirement for when a master should start processing a response. Although, I can't think of why you would want to artificially delay processing a response. As you've stated, the spec says that the silent interval must be at least 3.5 character times...

Why would an analog input be 0 if you've left it floating? An analog input will sense any voltage, whether it's directly connected or induced by a nearby signal. You should connect unused analog inputs to ground if you want them to stay at 0V.

Have a look at the BASpi from Contemporary Controls. It's an expansion board (HAT) for the Raspberry Pi. https://www.ccontrols.com/basautomation/baspi.php