Can't connect more than 2 USB devices

I can only connect upto 2 USB devices (through a USB Hub) to my XP Professional VM (Parallels desktop 3) on my MacBook Pro. The Parallels manual says up to 8 USB devices can be connected. Is there any solution?

 

What build are you using? What happens if you try and connect multiple devices?

 

my Parallels is build 5582. I use my development tools (Microchip's MPLAB, emulator, programmer, all through USB). I connect the first USB device, no problem and the VM accepts and runs the driver for it. Also, no problem for second device, both work fine. But when I connect the third one (USB-RS232 converter), the VM says no more USB device can be connected and prompts me to disconnect some. I tried both USB ports on my MacBook Pro, the result is the same.

Is it because of some settings in either the Mac OS or Parallels that prevents the VM from accepting more than 3 USB devices? I have never seen this problem on any Windows PC.

 

Are you using Powered or unpowered USB hubs? Could it be a power issue?

 

No, my USB hub is a powered one. I have been using the same setup (i.e. 4 USB devices) to connect to my Windows notebooks, for the past 8 years altogether I have used 3 notebooks running XP Home, XP Professional and Vista Home Premium OS. On Windoes I never have any problem connecting to 3 or more USB devices. So I would not expect the Mac notebook to have problem for USB since USB is really an Apple invention. I guess it could be due to some settings on the Parallels desktop. Has anyone faced this problem before? Earlier, after I purchased my Parallels license, I submitted a request to report my problem on DVD video playing, but I received no reply at all after a few emails. So I really hope this forum can offer some tips for me.

 

Well, can you connect those multiple devices to OS X?

 

Sorry for not responding to the post, as we were having Chinese New Year festival. I tried connecting several USB devices to the VM and found the following results:
- all are detected and reported by Mac OS (System profiler)
- VM (Windows XP) can detect each individual device and connect more than 3 USB devices, except the 3 devices that I'm using for my development work.
- these 3 devices are Microchip ICD2 programmer, Microchip ICE2000 USB converter and Prolific USB-RS232 converter. I can connect any two of these 3 devices to VM, but not all 3, as the VM will reject the 3rd one.

I suspect these 3 devices may be sharing something that the VM didn't allocate enough. Previously in my Windows notebooks (XP, Vista), I have no problem connecting these 3 devices to the same computer.

 

chengjm,
please tell me more about this devices. Are they USB 2.0 or USB 1.1 devices?

Best regards,
Stacey

 

Cheng, glad you found where the problem is... Stacey will be the best to help you from here.

 

Hi Stacey,
I checked with the manufacturer, the two Microchip (www.microchip.com) devices (ICD2 and ICE2000 USB Converter) are both USB 2.0, and the USB-RS232 (Prolific) could be ver 1. On my Mac, it reports these devices under USB High-Speed Bus, with speed up to 12 Mb/s. I plugged the ICD2, ICE200 USB Converter, USB-RS232 converter and a Maxtor 320GB hard disk into a single powered hub and plug to my MacBook Pro USB port. The Maxtor hard disk works as my time machine backup drive and it works fine. Besides the earlier problem that all three devices (ICD2, ICE2000 USB Converter and USB-RS232 converter) cannot be enabled at the same time, there is one other problem (which, to me, is more severe than the earlier one). The problem is that when I use ICE2000 USB converter alone (directly into MacBook Pro USB port), it will fail to work with the emulator software (MPLAB from Microchip) after a few seconds. After checking for several hours, I found that as long as the USB icon (at lower right corner) is flashing, the set up will work fine. But once the USB icon stops flashing, the USB converter will hang and the MPLAB program will lock up indefinitely. This never happens in the real Windows XP machines (which I have used for many years). I believe the ICE2000 USB converter is a time-critical device and if it loses some sequential data from the OS layer, the MPLAB will hang as the ICE2000 USB converter is functioning as a hardware emulator (I'm developing firmware using Microchip's 8-bit CPU). I hope you have some solutions for me, as I really don't want to go back to the Windows computer again!

Regards,
JM Cheng

 

chengjm,
the higher maximum speed for USB 2.0 is 480 Mbit/s, while the full-speed of USB 1.1 is 12 Mbit/s. That is why, I suppose that all of your devices are USB 1.1. And that will explain the problem you have with plugging three devices at the same time, because Parallels supports 8 USB 2.0 and 2 USB 1.1 devices at a moment.

Please open 'Configuration Editor' of your VM ('Edit' -> 'Virtual Machine') and provide me with a screenshot of 'USB Controller' tab.

Best regards,
Stacey

 

Hi Stacey,
Here's the screen capture in attachment. There doesn't seem to be much info though.
Even though the VM accepts only 2 USB 1.1 devices, I can still live with it, because I can enable or disable the devices as I work with them. The ICE2000 USB Converter must be on all the time, while I can have just one of the other two USB devices enabled as I need them.
However, I'm more concerned with the failing of the ICE2000 USB Converter after a few seconds of working. When it fails, my CPU emulator (ICE2000) still runs but it loses the comms link (through the USB) with the main program (MPLAB) on my computer. There seems to be some difference between the hardware USB and the VM USB which may not be able to cope up with isochronous data. But this is just my wild guess. I have also set the option to optimize performance for VM (rather than Mac OS). But this does not help. Is there a way to set the priority of a specific USB device over others (including those belonging to Mac OS)?

 

Here's the USB device tree under Mac OS System Profiler.... the 2 vendor specific devices are the Microchip USB devices.

Best regards,
JM Cheng

 

You can try to set 'Connection options' in 'USB Controller' tab to 'Connect to Guest OS'.
Will it help?

Best regards,
Stacey

 

Hi Stacey,
I tried your suggestion of 'Connect to Guest OS', no, it doesn't help, no difference.
As this USB device (ICE2000 USB Converter) is very important to my work, I am ordering another Windows XP license to test with the VMware Fusion VM on my Mac before giving up on Mac and return to PC to use this device. Of course I will continue to use my Mac (and Parallels) for other computing tasks. This episode shows that there is indeed some difference between the direct PC USB port and Parallels' VM USB ports.

Best regards,
JM Cheng

 

Just an update to this thread. I purchased another Windows XP and installed the VM on VMware Fusion and all my USB devices are now working as before (when I was using a real Windows PC). I can connect all 3 devices (USB 1.1) at the same time, and also the ICE2000 USB Converter is fully working. VMware Fusion also has a beta version of an Importer (runs on Mac) that converts the Parallels' VM into that of VMware Fusion's format. But it didn't work on my files because of some partition problem in my original Windows disks.

 

I know this is an old old thread but I am having a similar problem and I think I may have found the answer at this link here. http://kb.parallels.com/en/4872

 

I don't know if your problem has been solved. My USB device is damaged, can I help solve it?

 

Hi, could you share more details with us, please?