For oscam and other card reader sw, it helps to have the same ttyUSB* number after each reboot. To manually select the same boot order of several ttyUSB devices you need to edit the file udev.rules in /etc/udev/rules.d/

First plug in your USB device.

With the help of the command:

udevinfo -a -p $(udevinfo -q path -n /dev/ttyUSB0)
Look for ATTRS{X} lines and select a line that works for you, if you have several identical devices you might use ATTRS{serial} if not you can use ATTRS{idVendor} like I do.

Open the file udev.rules in notepad++ or other unix compatible notepad and add your line under #USB devices

SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", ATTRS{idVendor}=="067b", SYMLINK+="ttyUSB0"
This will make my USB2Serial (pl2303.ko) device come up as ttyUSB0 instead of random ttyUSB*.
Add a line for every ttyUSB* device you have connected.

Save the file and reupload it. Done.

Best regrads!