but after pressing "connect" I am getting the message "Can't open device".
Any ideas, where to look for the problem (e.g. do I have to consider some settings at the Rigol)?
My guess is you don't have permissions to use the device. My scope is usbtmc4 (I have a lot of scopes ;-) ). Here's an ls -l of /dev/usbtmc4:
crw-rw-r-- 1 root plugdev 180, 4 Jun 7 08:32 /dev/usbtmc4
Note that root owns it but the group is plugdev and I'm a member of the plugdev group (type groups from a prompt to see).
On Kubuntu and similar this is handled by udev. I have a feeling I have sigrok installed and it sets that up properly, so my bad!
If you can test this, I will add it to the .deb file at least.
As root, make a file in /etc/udev/rules.d name the file 40-rigol.rules
It contains:
ACTION!="add|change", GOTO="rigol_rules_end"
SUBSYSTEM!="usb|usbmisc|usb_device", GOTO="rigol_rules_end"
# Rigol DS1000 series
ATTRS{idVendor}=="1ab1", ATTRS{idProduct}=="0588", MODE="664", GROUP="plugdev"
# Rigol DS2000 series
ATTRS{idVendor}=="1ab1", ATTRS{idProduct}=="04b0", MODE="664", GROUP="plugdev"
# Rigol DG4000 series
ATTRS{idVendor}=="1ab1", ATTRS{idProduct}=="0641", MODE="664", GROUP="plugdev"
LABEL="rigol_rules_end"
-OR- install sigrok which you want anyway (sudo apt-get install sigrok).
After a restart (or restart udev and replug the scope) I bet it works.
Let me know, please and thanks for the report.