In this three terminal rs485 to USB adaptor, there is 121 on the R5 . But the problem with this adaptor is ,the port of this adapter is com11 , whereas in the modsim application there are only 9 ports and one tcp / modbus port . Can you please help me in this situation...

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 supply is isolated or not.

I use the USB cable connected to computer to power the orange pi.

That two terminal USB to rs485 adaptor is enough to use , any how it is directly connected to computer so there is no need of ground pin right, and also by default there is no R7 resistor.

If only that three terminal USB to rs485 adaptor is mandatory, then I have to use the soldering and I have to remove it . Can you suggest the best way .

And also what should be the outcome , and how to know that the communication is established or not?

 

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 RS-485 communications is working. Once you've confirmed the hardware works, then move on to using ModSim and your own Python script (possibly in conjuction with the PyModbus library) to test Modbus communications.

 

Yeah am using putty along with orange pi. As I said that I established a communication with Orange pi and Arduino with rs485 , I used putty where I login to the orange pi and I cloned git in it and I tried different python scripts,and I got the response in the Arduino IDE .

I didn't get ,what to confirm or how to confirm that rs485 communication.

 

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 only two wires for the RS-485 signals if you are powering the Orange Pi via USB from your computer).

Open PuTTY on your computer, select Serial for the Connection Type, enter the COM port number for your USB to RS-485 adapter, and enter your desired baud rate. Click the Open button to start the terminal session.

On the Orange Pi, download and install a terminal emulator, such as Minicom. Open Minicom for the TTY port associated with the pins you've connected to your MAX485 module. When you type character in Minicom, you should see then in PuTTY on your computer. And when you type characters in PuTTY, you should see them in Minicom.

You may also be using PUTTY to SSH into the Orange Pi. In this case, you would have two PuTTY sessions open on your computer.

 

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 only two wires for the RS-485 signals if you are powering the Orange Pi via USB from your computer).

Open PuTTY on your computer, select Serial for the Connection Type, enter the COM port number for your USB to RS-485 adapter, and enter your desired baud rate. Click the Open button to start the terminal session.

On the Orange Pi, download and install a terminal emulator, such as Minicom. Open Minicom for the TTY port associated with the pins you've connected to your MAX485 module. When you type character in Minicom, you should see then in PuTTY on your computer. And when you type characters in PuTTY, you should see them in Minicom.

You may also be using PUTTY to SSH into the Orange Pi. In this case, you would have two PuTTY sessions open on your computer.

I'm facing issues while detecting the port for rs485(max485) which is connected to orange pi , I tried using the command "ls /dev/tty*" , but there are lot of available ports how to identify the correct port.

 

Actually i have done this ,i dont know whether its correct or not , the max 485 module is connected to the orange pi and the wires of that module is connected to usb to rs485 adapter which is connected to laptop.
Then i login to orange pi using putty(ssh) and executed a python script , then i opened a new putty session of serial connection in which the com port i selected is the orange pi which is connected using USB cable connected to laptop . i tried to open the com port of usb to rs485 adapter , but this session is not opening. I need your help ....

 

I'm facing issues while detecting the port for rs485(max485) which is connected to orange pi , I tried using the command "ls /dev/tty*" , but there are lot of available ports how to identify the correct port.

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, doing RS-485 using a UART on Linux has additional complications, as the Data Enable (DE) line also needs to be controlled. Many Linux distros have RS-485 modes available for the UART drivers, but you may need to manually configure which GPIO pin is used for this purpose and you may need to enable this functionality. You will need to research this on your own in the Orange Pi and its Linux distro's documentation. Alternatively, your software itself could control the GPIO pin for the Data Enable line manually when performing RS-485 communications.

If the above seems too complex, you may want to consider using a USB to RS-485 adapter on the Orange Pi, as this would remove the above complication. USB to RS-485 adapters under Linux are typically ttyUSBx (or sometimes ttyACMx) devices, where x is the serial port number.

 

Actually i have done this ,i dont know whether its correct or not , the max 485 module is connected to the orange pi and the wires of that module is connected to usb to rs485 adapter which is connected to laptop.
Then i login to orange pi using putty(ssh) and executed a python script , then i opened a new putty session of serial connection in which the com port i selected is the orange pi which is connected using USB cable connected to laptop . i tried to open the com port of usb to rs485 adapter , but this session is not opening. I need your help ....

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) trying to use the COM port.