You cannot use the Microsoft Communications ActiveX Control to access a Universal Serial Bus port (832678)


The information in this article applies to:

  • Microsoft Visual Basic Enterprise Edition for Windows 6.0
  • Microsoft Visual Basic Professional Edition for Windows 6.0
  • Microsoft Visual Basic Learning Edition for Windows 6.0

SUMMARY

This article discusses why you cannot use the Microsoft Communications ActiveX control (MSComm) to access a Universal Serial Bus (USB) port.

MORE INFORMATION

The MSComm control is implemented in the MSComm32.ocx file. The MSComm control permits you to provide serial communications that transmit data and that receive data by using a serial port for an application. You can use the MSComm control to provide serial communications that use a communications (COM) port. A COM port is a serial port. However, you cannot use the MSComm control to provide serial communications that use a USB port. A USB port is not a serial port. A USB port is a bus. Therefore, by design, you cannot use the MSComm control to access a USB port.

A USB port is a bus that is designed to provide Plug and Play functionality for some peripheral devices. A USB port behaves more like an integrated device electronics (IDE) controller than like an ordinary serial port. Therefore, you cannot access a USB device if you are in user mode. To access a USB device, use an appropriate device driver that can access the USB device in kernel mode. Some USB devices include device drivers that handle this type of communication.

Note You cannot use the MSComm control to access a USB serial adapter that is connected to a USB port. If you try to use the MSComm control to access a USB port, you may receive the following error message:
Run-time error '8015': Could not set comm state, there may be one or more invalid communications parameters.

REFERENCES

For more information about the MSComm control, visit the following Microsoft Developer Network (MSDN) Web site:

http://msdn.microsoft.com/library/en-us/comm98/html/vbobjcomm.asp

For more information about the USB port, visit the following USB Web site:

http://www.usb.org/home

Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Modification Type:MajorLast Reviewed:1/9/2004
Keywords:kbUSB kb3rdparty kbControl kbSerial kbCommPort kbinfo KB832678 kbAudDeveloper
©2004 Microsoft Corporation. All rights reserved.