Typically the generators will get assigned the first available COM port starting with COM3. If there is a driver already using the port, it will skip to the next one.
Perhaps at one point you had Gen 1 on COM3 and COM4 was in use or got hung, and Gen 2 got installed on COM5.
Did you recently use the Utils, Remove Unused Generators from Registry command?
If at any time COM4 was freed, it is possible that Gen 2 was then installed on COM4.
Typically, the generators will stay on the COM port they are assigned until the port layout changes -- hung port, new device, etc.
You can manually assign the port numbers by going to Device Manager, Port (COM & LPT), find the generator driver based on the current COM port assignment and then right click to access the properties dialog box.
From here, go to the Port Settings tab, Click Advanced, and on the Bottom Left is the COM Port number assignment. If you are unable to select a port it is because it is marked (in use). You will first need to clean up whatever driver/device is on that port.
Once you have reprogrammed the port numbers, unplug the primary USB cable from your HUB, wait 10 seconds and then, plug it back in. Verify that the port assignments did not change. If it did, then you will need to prune and purge and rebuild the generator to com port device list from scratch -- meaning you uninstall all Silicon Labs CP210x drivers, and then plug one generator in at a time and assign the port numbers as you go.
When doing it this way, try to keep the cables on the USB hub in order. Meaning, COM5 in first port, COM6 in second port, etc... This will help ensure that when they are rescanned, they are put back on the port you assigned rather than shifting around taking each other's place.
Hope the above helps. Of note, this is not as easy to do on XP, but works like a charm on Windows 7 on up to Windows 10.
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