Modbus RS485 VFD Not working

Hi,
I tried to use RS485 to control my YL620-A VFD. Unfortunately I can't get it to work. I followed this guide github.com/xsnoopy/LinuxCNC-Yalang-yl620...Modbus-ClassicLadder . When I start the Machine, I get the error "Failed MODBUS communications" (picture attatched).
Also I've attatched all my config files.
I've already tried using a new USB-adapter, as they aparently sometimes don't work. Also tried switching the two cables. Do I need a common ground between the Computer and my VFD, other then through mains voltage? What else could I try?

Thanks,
Max

Try to buy a decent RS485 adapter with GND, if possible. ModBus sometimes wants a 120 Ohm resistor on both ends.

ModBus is not super reliable, so include a WatchDog in your setup.

Check your ttyUSB0 permissions:
ls -l /dev/ttyUSB0

Add your user to the "dialout" group
sudo usermod -a -G dialout $USER

Temp. change permissions and try again:
sudo chmod 666 /dev/ttyUSB0

Use a tool like ModPoll to test basic communication before you move on to LinuxCNC/ClassicLadder.

www.modbusdriver.com/modpoll.html

I bought this USB to RS485 Adapter ( www.amazon.de/Waveshare-Industrial-USB-R...sb%2Caps%2C80&sr=8-3) , still no success. On this device I could also only ever see the TX led blinking. So I guess the VFD never responded in any way. I resetted my VFD to factory settings and only changed the parameters necessary to make the spindle work again and to enable Modbus. Still the same result, apart from the VFD now showing and blinking 'F 50.0' all the time (before the reset it always blinked 'F400.0'. I guess I did not change all the settings as I did the first time).
I also checked my permissions, added the user to dialout and changed the permissions. Because the TX led is blinking, I don't think the PC or USB adapter is the problem.
For all this testing I used Modpoll, which always responds something with 'timeout' in the terminal.
I have no idea what else to set up in the VFD to make this work...
 

Modpoll has to work before you can move on. Might be VFD parameters or settings. Hard to tell but if parameters don't match or the register address is wrong, you might get a timeout.

There is a thread related to your VFD / Modbus:

forum.linuxcnc.org/24-hal-components/391...modbus-communicaiton

Maybe there is some useful information in there for you.