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Thank you for the USB to RS-485 adapter documentation. According to that documentation, you do not need to connect jumper wires to the adapter. Refer to the image under 6. Connection instructions->Type-C TO RS485->2. RS485 point-to-more/ half duplex 2-line communication. You should have wires...

Unfortunately we cannot be more descriptive with our responses until you are more descriptive in explaining the problem. We need to know all equipment involved (vendor and models), what Modbus software is being used (if any), what USB to RS-485 adapters are being used (if any), the exact steps...

If swapping your A and B wires results in the same behavior as when the Netbiter is off or when the RS-485 wires are disconnected, then it is very likely the wrong polarity and you should swap the wires back. You should not be receiving a "Received invalid response to modbus query" when the...

A Modbus RTU checksum error is not caused by parity. The Modbus checksum is at a higher level. The parity bit in each character is a sort of checksum, but on the scope of each single character in the Modbus frame. The Modbus checksum is performed after successful reception (i.e. no parity...

What error message does ModScan show if you disconnect the RS-485 wires? If it doesn't show a timeout error, there may be an issue with your USB to RS-485 adapter. You may need to try a different adapter. When you swap the A and B wires, it should be done at one end only. The Netbiter does...

When communications is successful, ModScan's Polls and Responses counters will increment together and there will be no messages in red text at the top. As for which registers to access on the Netbiter, refer to page 32 in the manual I linked in my previous response. Analog Input 1 is register...

Slave ID is labeled "Device ID" in ModScan and it is set via dip switches on the Netbiter (refer to the manual for details https://www.netbiter.com/docs/default-source/netbiter-english/manuals/hms-hmsi-27-228.pdf) Yes, 0V is equivalent to ground.

Try swapping your A and B wires (with some vendors A is positive and B is negative, but for others, B is positive and A is negative). If your USB to RS-485 adapter has a ground terminal, connect it to the Netbiter's ground terminal in addition to the A and B wires (3 wires total). Double check...

How many terminal blocks does the Netbiter IOX have with RS-485 signals (labeled A and B)? I believe it only has one, therefore it has only one RS-485 port.

Since the Netbiter IOX has only a single RS-485 port, I'm assuming you have both the Beckhoff and your computer connected to the IOX's single RS-485 port and communicating at the same time. Modbus RTU allows only one master to be on the network. Both the Beckhoff and your computer running...

Use Device Manager to confirm the COM port number of your USB to RS-485 adapter. If you changed the port number through the device properties in Device Manager, you may need to restart PuTTY or even reset your computer. Also make sure you don't have any other software (or another PuTTY session)...

Typically under Linux, serial ports are ttySx devices, where x is the serial port number associated with the UART. For example, ttyS1 may be associated with UART1. The correct serial port number depends on which TX and RX pins on the Orange Pi you've connected to your MAX485 adapter. However...

Here are more complete instructions on how to test RS-485 communication between your Orange Pi and your computer (with a USB to RS-485 adapter). Connect your Orange Pi to your MAX485 module. Wire the MAX485 module to your USB to RS-485 adapter, which is connected to your computer (you can use...

Yes, if you are using a USB cable connected to your computer to power the Orange Pi, you can use the two terminal USB to RS-485 adapted without needing an explicit ground wire. To test communications, I suggest using a terminal emulator software on your computer, such as PuTTY, to confirm...

In Device Manager, go to Properties for the adapter and you can choose a new COM port number.

It depends on how the Orange Pi is powered. If you're powering the Orange Pi through a USB cable connected to your computer, then no, you don't need a 3rd wire for ground in your RS-485 wiring. If you're using a dedicated power supply for the Orange Pi, though, it depends on whether that power...

Yes, RS-485 devices need a common ground. Unfortunately it's not always obvious how to properly establish a common ground, as some devices expose only the + and - signals and no ground signal (as is the case with one of your USB to RS-485 adapters). There are two common methods for making ground...

And does communication between the Arduino and Orange Pi work when using one MAX485 module without the R7 resistor and one RS-485 to USB converter?

I don't understand this statement. From your image in post #3 above, R7 is clearly installed. Did you mean DI and RO pins of MAX485 are connected to the TX and RX pins of the Orange Pi? Regarding your RS-485 wiring, please see my comment from post #4 above: This applies to RS-485 connections...

Can you provide details on the specific RS-485 adapters or modules used and all connections made for both scenarios? Keep in mind you sometimes need to swap A and B signals, as some vendors use A as +, while others use B as +. Did you remove R7 from your MAX485 module? Also, did you double...