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Device Connection Issues (CP210x)

MD300I2, MD300W1, MD100A1, MD100E, CMS50EW

The single most common problem associated with devices that use the Silicon Labs CP210x USB to UART Bridge driver is related to connection. This driver is used by MedView, Keep-It-Easy, and SpO2 Assistant. In this article, we will call the software you can installing "MKS." The connection problem can be caused by any one of the following :

  • The cable is not plugged in properly (see connector issues)
  • There is a time delay for the driver to find the device.
  • The device is not powered on or connected to PC when the program is started.
  • The driver CP210x USB to UART Bridge is not installed properly.
  • Windows 8 prevents the driver installation.
  • USB serial IO port conflict
  • The software has conflict with another software running.
  • The software cannot find the port (for MedView only).
  • The device has no data.
  • The software only runs on Windows, not MAC.
  • The USB cable that comes with the device has an interface chip embedded in it. Regular USB cable does not work.

Earlier version of the driver does not support 64-bit Windows. This is no longer an issue with the current release.

The items documented here are mostly from our own painful experience.

Time delay

When the driver tries to connect to the device for the first time, it may take a few minutes to establish the connection. Sometimes it may take a few trials to succeed. Patience is needed here. In one occasion, we came back a few hours later and discovered that the connection was working.

Device is not on

The device will turn off automatically after a short period of inactivity. Make sure the unit is on and connected to PC before starting the software; otherwise you would get an error message.

Windows 8 driver signature enforcement

Drivers from ChoiceMMed and Contec Medical Systems are not digitally signed and they cannot be installed in Windows 8 without going through Advanced Startup. For more details, see Installing unsigned drivers in Windows 8.

Device driver not installed properly

You can check the driver installation by following the following steps:

  • Go to Control panel and then Add or Remove Program, you should see the program "Silicon Laboratories CP210x USB to UART Bridge (Driver Removal)" as shown below.

Add or remove program screen

  • Connect your device to the PC, turn it on and then go to the Device Manager (right click on Computer >> Manage >> Device Manager, you should see your device shown as "Silicon Labs CP210x USB to UART Bridge (COMx)." If you unplug the device, the entry would disappear from the device manager screen.

Device manager screen

If you do not see the USB to UART Bridge in the "Add or Remove Program" list, your driver has not been installed. You would need to install the driver manually.

If you do not see the USB to UART Bridge in device manager, either the driver is not installed properly or there is a software conflict or USB serial IO port conflict.

Version conflict

If your computer already has another version of the USB to UART Bridge installed, the new one may not installed properly. The newly installed software may not work with the latest version of the driver. For example, the CP210x driver from MedView would not work with SpO2 Assistant when we were doing the testing.

Software conflicts

The programs running on your PC are interfering with each other in accessing the COM port. One fix (see the section software conflict resolution for more recommendations) is to remove the offending program; however this works only if you know this is the problem and the trick is to find out the offending programs. I am not aware of any easy way to determine the conflict. There are a few things you can do to look for hints.

  • Communication error messages (e.g. "Read COM failed") when running a program. This program is a partner involved in the conflict.
  • Error messages during system or program startup. The program generating the error message is another potential candidate.
  • Install the MKS software on another PC (preferably a clean PC without installed programs that uses the USB port). See next section on USB serial IO port conflict.

For one particular case, on a computer we used for testing various devices, we finally decided to reinstall Windows to solve the problem.

Problem software reported by our customers:

  • HotSync Manager from Palm
  • Lifecam from Microsoft

Resolving software conflicts

Possible fixes are:

  • Uninstall the offending program. Reinstall MKS.
  • Use another computer
  • Reinstall Windows
  • Isolate the conflicting devices to different instances of Windows using any of the following techniques:
    • Multi-boot: By installing multiple operating systems on the same computer, you can built a "clean" one and run the software on this copy. The drawback is you would require extra disk space and at least two disk partitions, one for each copy.
    • Virtual machine: See Microsoft Windows virtual PC, VMware virtual machine and Windows XP virtual machine. Each virtual machine would run within its own environment and would eliminate any interference. When building a virtual machine, do not copy from one that contains the conflicting software. Installing Windows Virtual PC is actually rather simple if you have Windows 7 Professional or Ultimate. The following steps are obtained from Microsoft. The procedure is not as daunting as it sounds.
      • Download Windows Virtual PC and Windows XP Mode installers from the Windows Virtual PC Web site (http://go.microsoft.com/fwlink/?LinkID=160479).
      • Install Windows XP Mode by double-clicking the file WindowsXPMode_nn-NN.exe (where nn-NN is the locale code, for example, en-US) and then completing the wizard that opens.
      • Install Windows Virtual PC by double-clicking either of the files Windows6.1-KB958559-x86.msu or Windows6.1-KB958559-x64.msu, as appropriate for your processor type.
      • Restart the computer.
      • Once the computer has restarted, click Start, click Windows Virtual PC, and then click Windows XP Mode.
      • Complete the wizard that opens. Be sure that you record the password provided during the setup process because you will need it to log on to the virtual machine.

These applications do not use a lot of resources. Any old computer running WXP would work. If you encounter any software conflict, just re-install Windows to get a clean machine.

Please email us if you find another conflicting software.

You should try to install the software on another computer first to verify the problem before trying multi-boot or virtual machine. These two approaches, though not difficult, require some expertise in installing Windows. There are many other advantages in running multiple instances of Windows on one computer, which has saved us many times in the past.

USB serial IO port conflict

If the computer has multiple installed software (e.g. webcam, MP3 player, PDA) that uses USB serial IO, they may interfere with each other. For example, an installed driver may think that a COM port is assigned to it even if the USB device is not connected and keep on sending data to the COM port. Another driver thinks that the COM port is available as there is no connected device and would start using it.

To find out which USB devices are causing problem, connect them all to the computer. Run and test them together. Look for error messages and strange behaviors.

Reinstalling software

You would need to uninstall both the software (MKS) and driver manually prior to any reinstallation.

  • Connect the device to the computer. Start up Device manager and look for an entry Silicon Labs CP210x USB to UART Bridge (under Ports, see diagram above).
  • Right click on the entry and select "Uninstall".
  • Check the "Delete the driver software for this device" box and click "OK"
  • Go to control panel >> add/remove program
  • Uninstall the software (Medview, SpO2 Assistant)
  • Uninstall all items related to the Silicon Laboratgories CP210x driver (there may be multiple entries for the driver).

You may want to reboot the system at this point prior to reinstalling the software.

After installing the software, restart the system to finalize the install.

Reinstalling driver

Remove the installed CP210x driver from "Add/Remove Program" and device manager prior to the reinstallation (see the section above for details).

The Keep-it-Easy software combines all the modules and driver into one executable and the driver cannot be installed separately. One has to reinstall everything.

For MedView, there is a program "setup.exe" within the usbDriver folder in the CD. Execute this program to reinstall the driver only. Remember to remove the driver first using the "Add & Remove Program" in control panel.

For SpO2 Assistant, you can download the driver form CMS50EW Reference page.

Installing the driver is a two-step process. At the end of the first step, remember to check the box labeled "Launch the CP210x VCP Driver Installer" prior to clicking the Finish button. The second step is the actual installation of the driver into Windows.

Software cannot find the port (MedView)

Start MedView and go to the New Data Capture screen, click "Extended" and manually select the appropriate port. The correct port is the one shown in Device Manager. For example, in the above diagram, the port is COM4.

New data capture screen

No data

Take a few measurements and try again.


You would need to find a Windows-based computer.


Please email us if you want to join into this ongoing study.

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