MAX and VISA displays extra COM port

From the Windows 2000 -> Control Panel -> System, it displayed that there are the following ports:
COM1 - Serial port
LPT1 - Parallel port
COM2 - USB-to-serial port
However, when checked with MAX & VISA, it displays an extra port:
ASRL1:INSTR (COM1)
ASRL2:INSTR (COM2)
ASRL3:INSTR (COM3)
ASRL10:INSTR (LPT1)
I don't know where does the COM3 comes from, or how to eliminate it. I have tried to take out the reference to COM3 on the visaconf.ini , but it reappears.
At the same time, I am having Labview crashes problem (access violation) after I communicate with the instrument connected via COM2 (Labview.exe crashes on a 2nd run of the same script, which needs restarting of computer before it will work again, for one r
un and crash again on the 2nd run). Does this problem has anything to do with the appearance of COM3?
Please help!
Thanks
Vanessa

Vanessa:
I believe COM3 is still in your registry under HKLM\HARDWARE\DEVICEMAP\SERIALCOMM. It is possible that it existed at one time previously and the system never deleted it (although this seems odd to me). You should be able to run regedit, find this key, and delete the COM3 string item in the right hand view.
Even though viFindRsrc is returning COM3, I do not believe that viOpen will succeed - it should return an error for that port since you say it does not really exist. In fact, MAX should show some kind of exclamation point or X through the icon. Does it do this?
Regardless of the MAX behavior, this should not affect your LabVIEW program in any way. I have no idea what is causing your crash but it is probably not related to this phanto
m COM3. If you think the crash is in VISA, I suggest you use NI Spy and enable Log to File with Fail Safe Logging selected. Then after the crash you can load the .spy file and see if any VISA call did not return.
Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments

Similar Messages

MAX and VISA Resources

I have MAX version 4.6.1 installed from NI-VISA 4.6.2. Recently I upgraded from LabView version 8.5 to 8.6 after which I have lost all previously used VISA resources. When I launch MAX it indicates there aren't any VISA resources found. I have tried adding VISA resource and I am able to validate the connection and verify connectivity using the VISA test panel. However, after I refresh VISA resources in MAX it loses the newly added (and saved) VISA resource. MAX returns the following error code:
0xBFFF0011 (VI_ERROR_RSRC_NFOUND)
Additionally, I have tried the following without success:
Removing MAX and reinstalling using NI-VISA without success.
Importing a colleagues configuration data.
Has anyone experienced this issue and know how to fix it?

Hello, did you reinstall drivers after upgrading LabVIEW? You will need to run the VISA installer again. As well as any other drivers you want to use in LabVIEW
National Instruments

VISA "Find" not seeing COM port but Win7 sees it

Allo. I'm trying to communicate via virtual com ports with a device with an FTDI chip. The device with the FTDI chip has both a USB type B port as well as a 9 pin dsub port, and I need to verify both ports work.
I'm using a laptop with Windows 7 and my program is in LV 2010. I have a Sabrent USB to serial cable to test the dsub port, and a standard USB cable to test the other port. I've installed the latest FTDI drivers and when I plug in both cables and look under Windows Device Manager, I will see both of them under unique COM port settings (usually COM4 and COM 5). So Windows sees and recognizes both virtual COM ports, and no yellow warnings.
However when I run the "VISA Find" function in LabView, it only sees COM5 (the Sabrent serial cable) but not the COM port using the USB type B cable. I send the results of the "VISA find" to a display and it will show other ports, like the parallel port, so I know it's seeing more than one port.
Any ideas why Windows can see the two COM ports but the "VISA Find" function can only see one? My guess is there's something with the FTDI driver set up.
Amateur programmer for over 10 years!

Yes, but its not for the faint of heart!
You can probably do what you want by using the refresh "F5" in MAX or add this token
[VISA-CONFIG]
ShowRegisteredDevOnly = 0
to C:\ProgramData\National Instruments\NIvisa\visaconfig.ini
Another thing to try is to recover the unused COM Port numbers each time you change the device. By default Windows will "Save" those previously connected COM port numbers an if it sees the device again it will re-assign the old number. This means that the COM number keeps getting larger and larger. At some point the PC's BIOS will say that's rediculous and you will experience trouble.
Programatically you could call
C:\Program Files\National Instruments\NI-Serial\NiPortConfig.exe to launch the same utility. there is probably even and unpublished switch to click just that one big button for you but I can't find it.
It looks like you may be running into some part of this known issue
Jeff

HyperTerminal sees a COM port but VISA does not

It should not be possible that HyperTerminal sees a COM port but VISA does not. Does anyone know why or have any ideas?
Here's some more info: I wrote a LabView (LV) program and deployed it (via the Application Builder) to some of our production department's PCs (some Windows XP and some Windows 7). We use it to set up products we design and manufacture through our device's USB serial port. The USB port is actually a virtual COM port (VCP) - a USB to Serial converter or "bridge". We have a custom driver for our device and since each device's USB bridge chip is programmed with a different serial number, every time we connect a new device to the PC the installer runs and assigns a new COM port number. This is so our customers can use multiple devices on a PC. Fine. On one of our production PC's we were close to COM900 ports (HyperTerminal sees only up to COM256) when suddenly Win7 would not allow any more. We were able to uninstall orphaned (non-present) COM ports from DeviceManager ("DM") by starting it from a command console (DOS window) with a special command-line switch, "set devmgr_show_nonpresent_devices=1" then "start devmgmt.msc" (I have this in a batch file). In DM View menu you can "Show hidden devices" and uninstall them as if they were connected. I've also tried uninstalling them the normal way when the device was actually connected. Either way, sometimes, not always, depending on the COM port number, after reusing that port number by installing a new device which picks up that old, freed-up number, LV VISA doesn't see it. In other words, when "Refresh" is clicked in the COM port VISA list box, any new devices installed should be and normally are seen. (Refresh is not needed if the application is started after the device's driver is installed. It is only need if the LV application is open with the new device is added.) However, HyperTerminal does see it and lists it in the Properties screen, the "Connect using..." list box. And the port works with HyperTerminal. (Of course we've tried rebooting after uninstalling and/or reinstalling the device, with the same results.)
When I've spoken to the NI Applications Engineers in the past about serial port issues (not about this problem) they have confirmed that if HyperTerminal can see the port then NI VISA should also see it. This is crazy. I am posting this in hope that someone can shed some light on this problem.
Thank you. -Ed

Good catch. Yes, we're using the Silicon Labs CP2102 and have created a "custom driver" installation package. Our new PCBs have a factory-programmed chip, so the PC reuses that COM port (COM3 on that PC). The problem is when we we re-program the CP2102 (setIDs exe) with our PID, and device strings (including the S/N), the PC runs our installer and assigns the next COM port number. I was hoping that maybe it would go up to 64K or something! Anyway, it surpassed COM256 but we ran into this problem when almost up to COM900.)
There is a registry entry for each SN device, which shows the assigned port. If we delete the key with regedit, the COM port database (don't know the file name) still has the port number. That's where Device Manager comes in. It seems to allow us to manually delete the ports, but it would take quite a while to delete 900. (I was trying to make a batch file for DevCon, but couldn't get it to see the HW ID of the devices in need of deletion.) So we tried manually deleting a few. After doing that Device Manager shows that Windows (and HyperTerminal) can reuse the port number when a new device (new SN) is installed, but, as you know from this post, VISA cannot see unless I manually add it in MAX.
I can't see how it has anything to do with the Silicon Labs driver. I might have to delete ALL of MY devices, then uninstall the driver files, reboot, then reinstall, as you suggested with the SiLabs driver. However, I don't see how VISA will now see these changes. VISA must have it's own database. That's what I thought deleting the ports in MAX would clear out, like a fresh install, but apparently not.
I've been through Silicon Labs' tech support on other issues and they've been able to help on some. I could run this by them.
BTW, have you noticed that Silicon Labs' chip and driver, while faster than NI's own "bridge" or serial-USB converter (I returned it because at $100 it's performance was worse than a $20 converter you can buy in Staples), is substantially slower than a real serial port? For example, our device can transmit 250 readings per second (a 12 byte string). A real serial port used with my LabView program can keep up, i.e.., graph & tabulate at that rate, but with a VCP we only get about 70 RPS. Same code. Can't figure this one out. They say the've tested the driver to 900 KB claimed. We're using 115KB here. Anyway, the VCP driver makes it look like a COM port which LV thinks it is. Why is it slower than a real port when the USB should be able to work almost 10 times faster than I'm using it (up to 1024 bytes per mSec per the full-speed USB spec, which SiLabs claims they verified)?
Anyway, I appreciate your help. Thanks! -Ed

How to use thunderbolt port with disks and DVI-display

Hello,
today I use a 15" MacBookPro and have attached 1TB LaCie with FW800 (for time machine) and DVI-Display using Mini-port.
Need to add more external disk space and look for Lacie 2 TB with thunderbolt connection (for storing mass of pictures in Raid1 version)
Is it possible to connect the new disk, the other disk with an Thunderbolt->FW800 adapter and the DVI-Display to one thunderbolt port?
What are the options I have, to get all three to work at the same time?

No, or at least not without additional hardware. You have too many end-points for one Thunderbolt chain.
You also have the problem that the Thunderbolt->FW800 adapter is not yet for sale.
If the new disk you get has two Thunderbolt ports (which not all do), you could daisy-chain the Thunderbolt->FW800 adapter behind it, but that adapter has to be at the end of the chain. The Mini-port->DVI adapter likewise needs to be at the end of a chain.
So, you can probably get all three connected at one time by connecting the "1TB LaCie with FW800 (for time machine)" to your FW800 port, while connecting the Thunderbolt->FW800 adapter (when available) to the second port of the new disk. I say "probably" because nobody has the TB-FW adapter yet to try it.
As for doing it on one Thunderbolt port with additional hardware, you might look into third-party docking stations being released in the next few months. The announced prices are in the low-to-middle hundreds. I won't mention brand names, as this is an Apple forum, but they aren't too hard to find by web search.
The highest-priced solution would be the Apple Thunderbolt Display, which gives you a FW800 port for your 1TB drive, a pass-thru Thunderbolt port for your new disk, and of course a 2560x1440 display (plus ethernet and usb2 ports you may not need). It's available now, in the uppermost hundreds. There are some refurbs in the online Apple Store at the moment at 15% off.

How to use shared variables to address multiple Watlow controllers on the same COM port

Hello,
I am trying to use LabVIEW 2010 to control 4 Watlow temperature controllers on one COM port. 3 are Model 96 and 1 is an EZ zone controller. Each controller has a unique modbus address, and I am trying to read from and write to individual registers (such as closed loop setpoint) using shared variables. I am getting return data when reading (although the data appears to be invalid), but am unable to change the value in the register by writing. How can I be sure that the Modbus server is sending commands to the correct controller?
Chuck
Solved!
Go to Solution.

Peter,
Thanks for the reply. I have actually solved that problem. I realized that the Modbus server address has to be the same as the controller's Modbus address.
I have, however, run into another problem. Perhaps you could help me with that. I have a system with 4 Watlow controllers, 3 are series 96 controllers, one is PID only and 2 are ramping. The 4th controller is an EZ zone. I am using RS485 for communications and the controllers are all wired in parallel for communications and power.
I have set up 2 Modbus servers for 2 of the controllers.
This is the first I have ever worked with Modbus based communications. I have successfully programmed using the Modbus read/write VIs, and am wanting to move to shared variables. My questions right now revolve around addressing, Modbus I/O servers and COM ports. Specifically, at this point, I know the addresses need to match up between the server and the slave device (Watlow controller in my case), how many servers can I create and use on one COM port? If the number is limited, is there a way I can specify an address that I want the server to talk to? Will the broadcast mode work to request data values from the controllers?
I'd appreciate any information you can help me with, or if you could point me to some sort of concise 'How-To' for Modbus communication.
Thanks.
Chuck

Programmatically assign com port

Hi
I have an applicaton that uses USB-Serial adapters (Keyspan). This system is in an open lab situation with multiple users and multiple laptops runing the LabVIEW program. Each computer's registry assigns different comports to the Keysapn USB-Serial converter. I've been able to query the registry and determine what com port Windows has assigned to Keyspan.
How do I take this info and programmatically assign a com port or Visa resource name that LabVIEW is to open? Is there some simple Visa property node for "Resource Name" that I am not finding or is this more difficult than my awareness?
All of the laptop computers will be using Windows XP and LabVIEW 8.6 runtime engine.
Thanks
Glen

You can take the com port name as a string and wire it into the VISA functions. It will generate a coercion dot, but it will work.
Message Edited by Ravens Fan on 03-16-2009 10:30 AM
Attachments:
Example_VI_BD.png ‏1 KB

Satellite A300-1BZ with Vista - Com Port has disappeared

Hi everyone.
My first time and I'm a bit of a duffer with technical stuff, so please be gentle with me!
A300-1BZ with Vista.
A while ago I installed 'CarSoft V.83' (Engine diagnosis) from CD onto my laptop. It asked me to verify the com-port.
I looked in the device manager and in the list I saw 'com-port 4'. Ok, we'll go with that then. Everything worked fine and I was happily talking away to my car.
Yesterday I went to use it for the second time and it said there was an error with the com-port and to 'verify' the com-port.
So, I got the device manager back up and there is no mention of any com-ports in the list! It was there the last time I looked and now it's vanished!
I was at a loss what to do so, I uninstalled the CarSoft and then re-intsalled it again. Got the same error message.
Went to device manager. Still no com-port 4 in the list, or anything that relates to a com-port.
I don't know how or if I can get it back.
Please help!

Hi mate
First of all there are no com ports. The com port which you could see in device manager was an virtual port created by car software.
What to say
I recommend removing the car software from the system firstly.
Then download the CCleaner and clean the system and registry entries.
Reboot the notebook and run the CCleaner again
After that install the car software again
Maybe it helps

Installing Windows on drive attached to extra SATA port

I posted this incorrectly into the MacBook Pro so I have reposted here:
I have a Mac Pro with 4x500GB drives in RAID 10. Since bootcamp can't be installed on this RAID setup I took the stock apple 250GB drive and put it into an external SATA enclosure.
I have since booted to that external sata disk (by holding down the option key during boot) installed bootcamp and partitioned that drive for windows XP. So the drive now has both OSX and a partition for XP that I made via bootcamp. After that was finished I clicked the key to "install Windows now" or whatever.
The plan here is to just turn on that external drive whenever I need to run windows or install firmware updates for the Mac since apple can't seem how to do either with a software RAID set in place on the existing 4 internal drives.
After doing the above steps I now have 2 problems:
1. When booting from a XP SP2 disk to install XP the only drives seen are the 4 internal ones and not the extra sata port that is connected. This leads me to believe that I need to slipstream drivers for the extra two unused sata ports into the install disk but am not sure, I am hoping for some input.
2. Now when I power off the external SATA drive the only way I can boot back into my normal OSX RAID10 setup is by holding down the 'option' key and choosing one of the 4 RAID10 disks that are listed. After I do this it boots fine but I have to do this every time I boot my system which get really old.
If I don't hold the option key down down the system will just boot to a black screen asking me to "insert boot media". It seems like it is stuck in the bootcamp mode so I need to figure out how to get out of it.
I wonder if I can just uninstall bootcamp from the external SATA drive to fix this so that my system will boot normally? I will give this a shot tomorrow b/c I don't have time tonight but I appreciate any helpful advice.
If anyone has any ideas on how to get XP installed while running RAID please share. I know I can use an IDE drive but I have 2 optical drives installed so that is out for the moment but I may need to do that if I can't get the SATA option working.

The enclosure is usb and eSATA (external SATA) the drive is connected via a SATA cable to a SATA 3.5" adapter plate on the back of the mac pro that is connected to one of the unused extra 2 SATA ports that are tucked away behind the heatsinks on the Mac Pro's motherboard. So it is SATA all the way to the motherboard, I am not using USB at all.
As noted above, yes you can install XP on an IDE hard drive and put it into the optical bay area but I have two DVD burners installed there and would like to use the setup I have now if possible.
I was able to fix my 2nd issue listed above thanks to a suggestion in another forum of going into my startup disk options and choosing my RAID 10 setup. Now my system boots fine.
So back to the issue of installing XP on one of those extra unused SATA ports, if we can find out what brand controller those 2 ports are (intel, siig, silicon image, etc.) we could slipstream the drivers into the XP CD and then the windows install should work. Coming from a PC backgrounds and having installed various versions of windows literally at least 500+ times I have had to use the 'F6' optoin to install SATA/RAID/SCSI drivers from a floppy hundreds of times. The problem here is that we don't know what brand hardware it is or if it is possibly an issue with EFI not enabling those ports or something unless OSX boots, because booting to OSX connected to one of those extra ports works fine.
I guess I should also just ask again to be clear: You CAN'T install bootcamp on a RAID setup correct? Because I get an error everytime I try to run the bootcamp setup assistant. Geez, I wish apple would just enable the native RAID support built into the intel southbridge, that would solve the bootcamp problem, the RAID 10 setup problem where you can't setup RAID 10 via the GUI, and also the fact that you can't install any firmware updates to the box.
MB Pro Mac OS X (10.4.8) Mac Pro 2.66, 4x500GB RAID 10, 1GBx4, X1900XT MB Pro 2Ghz Dual Boot w/MCE 2005

How diagnose the extra SATA ports on the Mac Pro (early 2008) logic board?

I have had two SSDs in an OWC multi-mount in the second optical bay, one for Lion and one for Photoshop scratch. However, I recently began having intermittent boot problems. Sometimes there wouldn't be an Apple symbol upon boot/reboot, yet sometimes there would and the computer would boot. I have not experienced any crashes, kernel panics or such.
I thought the Lion SSD was faulty so installed Mountain Lion on the scratch drive, a Mercury Electra 3G which I have recently received as a replacement from OWC due to a previously faulty SSD. However, immediately there were boot problems from that SSD.
I have a feeling there is something wrong with the two extra SATA ports on the logic board. I am now booted off the Lion SSD placed in an external USB enclosure, which works but is a bit slower (I will get a bracket to install that SSD in the ordinary internal bays).
My question is how I can diagnose the logic board generally and specifically the extra SATA ports. I have Tech Tool Pro 6. I also thought I had AHT but on the Leopard DVD 1, which came with the Mac Pro (10.5.2) and on which AHT is supposed to be there is no trace of AHT. Odd. Booting from that DVD will only bring up the Leopard installer.
Btw I do think the Electra is broken because I am unable to boot ML from it in the USB enclosure.
Grateful for any ideas how to check my logic board.
Cheers
/p

If you could move the drives easily to another location then you could test the drives and also - make backup images! just to be safe. SSDs and their firmware and problems are almost all too common, even this last June a large issue with SandForce which OWC uses in some/most of theirs, and I get the feeling they are usually behind in testing and sending out firmware updates.
Corsair, Crucial and Intel have all had issues since it surfaced in May.
Diagnosing a motherboard with Apple Service Diagnostic CD is one thing. Swapping out SATA cables though no. WD Lifeguard does check communication to an SATA device drive and can - but you need to see the device in Windows or their boot CD (linux I imagine). Quite good utility though maybe not for an SSD.

Timeout on COM port

I have two ModBus vi's which I have combined into one in order to avoid two separate vi's running at the same time and both requiring the COM port. I've taken the beginners approach and created a sub vi for each and then called them in a new vi. Amazingly, one of the sub vi's actually runs, but the other gives a timeout error.
Can anyone tell me a better approach please ? I've attached the vi for viewing. Many thanks !
Solved!
Go to Solution.
Attachments:
COM 2 Share.vi ‏17 KB

Thank you. I've modified the vi and now the stepper routine will run once, but the power reading routine not at all. It was the other way round before. I need to set the vi to run continuously so that as I develop the vi more, the power readings will provide the input to the stepper routine. I'm sure I've made a novice mistake in connecting the error wire. I'd prefer to pursue this in preference to the semaphore for the time being.
Are you able to point out my error ? Many thanks !
Attachments:
COM 2 Share_2.zip ‏156 KB

Using VISA and RS232 devise , loosing the COM port .

Using VISA and R232 devise communicating fine with labview and I can Read and Write.
however, I want to turn OFF the devise, then turn it ON again (part of the test), and be able to continue .
The COM port is not communicating . unless I turn both the devise off and Exit LV then restart again.
How to do that without restarting LV.
thanks

" Is there a better way to make sure its closed and driver is not hanging onto the connection? "
you could try a command like " devcon disable usb\vid_0CD5*0003~" and then "devcon enable usb\vid_0CD5*0003~"
( you will need to figure out the ID of your device, my example is for a LabJack U3. )
Get the devcon.exe-utility from microsoft.
but as mentioned before, just watch what happens with device Manager (' run devmgmt.msc')...
to enable/disable a device in a VBS script you can use below example, (As Administrator!)
Option explicit
Dim oShell
set oShell= Wscript.CreateObject("WScript.Shell")
oShell.Run "RunAs /user:Domain\USER ""cmd"
WScript.Sleep 100
oShell.Sendkeys "USERPASSW"
WScript.Sleep 500
oShell.Sendkeys "devcon disable usb\vid_0CD5*0003~"
WScript.Sleep 1000
WScript.Sleep 100
oShell.Sendkeys "devcon enable usb\vid_0CD5*0003~"
WScript.Sleep 1000
oShell.Sendkeys "exit~"
Wscript.Quit
My reason for doing it this way is that my USB device didn't respond to any of my calls from Labview. Enable/Disable solved the issue...
The thing I particularly hate about above VBS-script is that I need to send the Admin password in plain text...

Why is my com port missing from my list of VISA devices

Hello all,
I have an Agilent E5810 ethernet to GPIB gateway. I installed Agilent IO library and chose to make Agilent my primary VISA because otherwise the devices on the gateway didn't show up in my VISA device list. Now all of my GPIB devices show up (local and via gateway) but my com port is missing. The com port is actually a USB to serial adapter. It shows up in device manager as CP2101 uart interface COM6. I reloaded NI-VISA but COM6 still oesn't show up. I reloaded Agilent IO and unchecked "make Agelent primary VISA" but that didn't fix it. It is also missing from MAX. I added COM6 ASRL6 but VISA doesn't see it
I think the root of my problem is getting Agilent VISA and NI VISA to work together but why won't my com port show up?
Thanks alot

Hello,
Can you please follow the steps outlined in the following forum post and reinstall NI-VISA and Agilent VISA?
Problem with NI VISA and Agilent VISA
If the problem still exists, please call 1-866-275-6964 and reference your call to your service request number (1194753).
Thank you,
Simran K
National Instruments
Applications Engineer

Max 9.2.2 doesn't recongize com ports

Max 9.2.2 doesn't recongize com ports.
Dell Precision 360
Windows XP
Two different computes, multiple attempts, downloads of software - same result: com ports don't show up.

Hi Test Engineering Leader,
It may help to clarify some of the different software components at work just to make sure you have to the ones appropriate for your application. MAX is an explorer that allows access to hardware devices using different drivers. DAQmx is one of the drivers, but it does not typically manage COM serial ports (it looks like DAQmx 8.6.1 does support one device over a serial interface, but this is an odd exception and using the serial port through this driver may be unpredictable). COM serial ports are supported in NI-VISA, which allows generic serial port handling and is a commonly used to build instrument drivers. There are other kinds of device drivers, like the 488.2 for GPIB devices, or NI Motion for cameras. You can check out the different Read-Mes to check out whether your device is support.
If you are trying to directly access the serial ports on your computer, then you should use NI VISA. If there is a particular device you are trying to communicate with, then it should be listed in the Read Me if the driver can operate it correctly.
So, just to verify, you have already installed the latest version of NI VISA? If so, then you should be able to open MAX and see an option called Serial & Parallel. If this is not listed, then check the device is probably missing from the OS: trying viewing it in the device manager. If it is missing in the device driver and you know it's there, try installing new hardware.
- Regards,
Beutlich

FTDI virtual com port driver (VCP) and Labview 2009 - random connection loss

Hi,
I am using an FTDI chip to go from USB to serial communication (FTDI Driver: 2.06.00). It seems to work at first but then after some time the connection gets lost ("connection for the given session has been lost" or "I/O error"). This happens in MAX as well as the built executable of the program I am running. Latest VISA drivers are installed - 4.6. I have tried flushing the buffer before and after communication with both visa clear and visa buffer flush vis. The lost connection seems to happen randomly.
I have seen other threads about this issue but they never reach a resolution. One thing i notice is that there are two FTDI devices in this system and only one fails, however when I unplug the working device the one that fails is able to connect again.
To sum up here are the system specs:
Windows XP SP3
FTDI 2.06.00 and older 2.04.02 drivers both fail.
2 FTDI devices on the system - they do get assigned different COM ports
Labview 2009 run-time
VISA 4.6 run-time
Thanks for any help.

We use Targus ACH63US Super Mini USB 2.0 4-Port Hub. It doesn't require external power but if you have a high power device you will have to plug the Targus hub into two usb ports on your pc (one provides power and the other does power and data transfer). They provide the usb Y cable to do this.

MAX and VISA displays extra COM port

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