Troubleshooting Windows Plug-and-Play and USB for Maxim Evaluation Kits


This application note helps you install and troubleshoot the CMAXQUSB and CMODUSB evaluation-kit interface boards. Frequently asked questions are answered.

Installing the CMAXQUSB/CMODUSB Device Driver

Figure 1

When you plug in the CMODUSB or CMAXQUSB board for the first time, the windows plug-and-play system detects the new hardware and automatically runs the Add New Hardware Wizard. (Windows 98 is shown in the screen shot. Windows 2000 and XP differ slightly.)

Figure 2

Specifying Search Location—CD-ROM Installation

Figure 3

The Add New Hardware Wizard asks where to search for the device driver. Ensure that the CD-ROM that came with the evaluation kit is in the CD-ROM drive. Be sure to check the CD-ROM drive box—otherwise windows will not be able to use the hardware.

Specifying Search Location—Updated Software from Maxim Website

If the CD-ROM was lost, or if a newer version of the software was downloaded and installed from the Maxim website (EVKit Software), then check the Specify a Location box. Use the Browse button to navigate to the location where the updated software was installed. Maxim software designed for CMAXQUSB or CMODUSB includes a copy of the device driver in the installed software directory.

Windows XP Reports Driver Is not Digitally Signed

During device driver installation, Windows XP shows a warning message indicating that the device driver used by Maxim uses does not contain a digital signature. This is not an error condition. It is safe to proceed with the installation.

Confirming Driver Selection

Figure 4

This screen confirms that the system found the right device driver. Click Next to continue.

Figure 5

Successful Installation

Figure 6

After you click Finish, the device driver is installed and the software is ready to go.

Windows Was Unable to Locate a Driver

Figure 7

This is what you will see if plug-and-play cannot find the correct device driver. This is really an error message. It is very easy to click the Next button without noticing this. Clicking the Next button now would tell the windows plug-and-play system to stop searching for a device driver and Ignore the new hardware as you proceed.

Unknown Device (Installation Failure)

Figure 8

This screen is an error message. It confirms that windows did not find the device driver that it needed; it will Ignore that device as you proceed. The only way to recover is to remove the Unknown Device node, which you can only see by going into the device manager while the device is plugged into the USB port.

Problem: Software Unable to Connect to USB Interface Board

Is the Operating System Supported?
Operating System Supports USB? Tested at Maxim?
Windows 95 No No
Windows NT No No
Windows 98 second edition Yes Yes (passed)
Windows ME Yes Not tested
Windows 2000 Yes Yes (passed)
Windows XP home edition Yes Yes (passed)

Is the USB Cable Correct?

The CMODUSB/CMAXQUSB boards use a standard USB A-B cable, which plugs into a standard Windows computer's USB port. To troubleshoot,

  1. Try using another USB A-B cable.
  2. Try plugging a known, good USB device into the computer's USB port.
  3. If using a USB hub, check whether the hub requires external power.

Was the USB Device Driver Installed When the Board Was Plugged In?

  1. Make sure that the CMODUSB or CMAXQUSB board is plugged into the USB port. Start Menu → Control Panel → System → Hardware → Device

Figure 9

You may see the USB ⇔ Serial or Maxim CMODUSB Command Module with a question mark icon next to it (see above).This indicates that Windows is ignoring the CMAXQUSB or CMODUSB hardware.

Remedy: Remove Failed Device Node

Figure 10

To remedy this problem, click the USB ⇔ Serial device node and click Remove. (This Unknown Device error node is only visible when the CMAXQUSB or CMODUSB board is plugged into the USB port.)

Figure 11

Click OK to confirm removal of the bad device node. Then close the device manager window, and unplug the CMODUSB or CMAXQUSB board from the USB port. The next time you plug the board into the USB port, the plug-and-play system will search for the device driver, as it should have done the first time.

If multiple USB ports were tried with no device driver, it may be necessary to plug the board into each of those other USB ports to remove each failed device-driver node.

Question: Is a Power Supply Required?

The CMAXQUSB and CMODUSB boards do not require an external power supply. The USB cable provides power as well as control. An optional external power jack was included in these designs to allow unregulated 6V to 12V power to be connected to daughter boards requiring a higher supply voltage. This power jack routes only to the daughter board connector; it is not used by any circuitry on the CMAXQUSB or CMODUSB board.

Question: Is USB 2.0 Required?

The CMAXQUSB and CMODUSB boards work with USB 1.0, USB 1.1, and USB 2.0 host ports. The device throughput is limited, so there is no speed increase from using an USB 2.0 port.

Removing the CMAXQUSB/CMODUSB Device Driver

  1. Make sure that the CMAXQUSB or CMODUSB board is plugged into the USB port.
  2. Start Menu → Control Panel → System → Hardware
  3. In the Device Manager tab, navigate to the node for the CMAXQUSB or CMODUSB board.
  4. Select the device and click the Remove button.
  5. Click OK to confirm that you are going to remove the device from your system.
  6. Unplug the CMAXQUSB or CMODUSB board from the USB cable.
  7. Start Menu → Control Panel → Add or Remove Programs → Maxim CMODUSB Device Driver → Remove

The next time the CMAXQUSB or CMODUSB board is connected to USB, the plug-and-play system will think it is seeing this board for the first time.