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Controlling the BLDC Motor Driver (GUX-9-400) by Communication (with Test Program)

Taesu Yim

As I posted earlier, I changed the control method of my GUX-9-400 from I/O control to communication control.

This post is about connecting and testing the motor driver.


  1. Connect

    Several parts are required for the motor driver to communicate.

    A connector is needed to connect the GUX-9-400, which uses RS-485 communication as its communication interface. A USB connection is required to control it with a PC.

    There are several options for this.




Using a conversion cable like this may be the most noise-safe way. Serial communication is always susceptible to noise. However, as shown below, the GUX-9-400 uses pins 8 (A+) and 9 (B+) for RS-485 communication, so most commercial cables will not work (typical cables use pins 3 and 4 for RS-485 communication).


So, I used the connector set below.



The photo above shows the connector that connects to the motor driver and the




This is the connector that plugs into the PC.

Connect pins 8 and 9 on the motor driver side to + and - on the PC side.



It is important to note that you must use a shielded cable. Unshielded cables will not communicate properly due to noise.




Once the connection is complete and the motor driver is powered up, you can check the connected port in the PC device manager. If you don't see the port, you should check the serial port driver for windows.





2. Connect

Once connected, it is ready to communicate. This motor driver does not allow you to change the driver's settings using communication. The functions that can be communicated are basic motion control actions: start, stop, brake, speed control (speed is signed and includes direction), and alarm reset. You can also monitor current speed, set speed, alarms, voltage, temperature, etc. This may not seem much different than the I/O control, but our testing allowed for more precise RPM control. To change the motor driver settings (address, mode, motor poles, etc.), you need a separate device called the OP-500. Unfortunately, I found no sites selling the OP-500 with English support.



The GUX-9-400's communication protocol is well described in the documentation below. It is easy to understand for those who have experience using the Modbus protocol. An example protocol is shown on the last page of the manual to make it easier for inexperienced users to test. There are many programs that can test serial communication on a PC, so I have not included them in this post. You can also utilize Python to send a simple protocol to the motor driver.


As shown in the example protocol, sending the command '01 06 00 79 03 E8 58 AD' (hexadecimal) to the motor driver will set the RPM to 1000. If you then send the protocol '01 06 00 78 00 01 C8 13', the motor will start spinning at 1000 RPM.



     3. Test Program

I have created and attached a simple program to test the GUX-9-400. You can test the motor's behavior by connecting and setting the port as described above. The following post will discuss how to use the program.

The test program is developed in LabVIEW and requires the LabVIEW runtime engine to run. In addition, a driver for serial communication(ni-visa) is also required and is attached.






Note: It is recommended that you disable all additional installation options when installing NI-VISA, as you only need to install the base drivers.





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