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USB Port Assignments

The M7-USB option, and all of the USB serial bridge cables from Raveon use the FTDI FT232R chip-set.  Raveon has an application note <here> that describes how the M7-USB option works.  The driver for the FTDI chipset is included with most versions of Microsoft Windows, and it may be <Downloaded Here>.

The when a USB device is connected to a computer, the FTDI driver software reads the device’s Vendor ID and serial number, and assigns an unused COM port number to it.   On the computer, it will create a virtual COM port, and any software that is designed to communicate with a serial device via a COM port, will be able to communicate with the Raveon data radio.  Once the FTDI device driver is installed, it will use the same COM port number for the same device plugged into the same USB port.  If the device is plugged into a different USB port on the computer, it will assign the device to a different COM port.

To force the computer to use the same COM port number for the same device, perform the following steps:

  1. Connect power to the Raveon data radio modem.
  2. Connect the Raveon device with the USB interface to the computer.
  3. Let the computer install the device driver. Follow the on-screen instructions.

Once the device driver is installed, you can determine the COM port number that was assigned to the device by using the Windows “Device Manger“.  You can find the Device Manager utility program on most computers by selecting Start > Control Panel > System  from the System window, select the Hardware table, and click on the Device Manger button.  Expand the Ports (COM and LPT) branch to see all of the COM ports on the computer.

The COM  port for the USB serial bridge will show up in the list as “USB Serial Port (COMxx)”where COMxx is the port number assigned to the USB serial device.  The image above shows as typical listing of COM devices on a computer with 4 built-in serial ports, and one USB serial bridge.

To force the FTDI driver software to always assign the same COM port number to the same device, perform the following steps after the FTDI device driver is installed.

  1. Double-click on the “USB Serial Port (COMxx)”  in the Ports branch of the Device Manger window.
  2. This will open a new window showing the USB Serial Port (COMxx) Properties.
  3. Select the Port Settings tab. Click on Advanced.
  4. One the Advanced Setting for COMxx window, select the COM port Number that you would like to assign to the USB serial bridge.
  5. Click OK.
  6. On the USB Serial Port (COMxx) Properties, click OK.
  7. One the Device Manager window, right click on the USB Serial Port item you just configured, and select “Disable”.
  8. Once the USB Serial Port shows as disabled, right click on it again and Enable it.

The Device Manger should now show the USB Serial Port with the COM port number that you chose. 

If you unplug the USB Serial device and reconnect it, it should appear back in the Device Manager list with the correct COM port as long as you plug the same device into the same USB port.

FTDI has an application note describing how to configure the advanced settings in its device driver.  The document is FT_000073.  This application note may be helpful configuring one computer to work with multiple USB serial devices or if you need to customize your installation.

 

 

Filed under: Hardware Information, Installation Information | Posted on October 11th, 2010 by John Sonnenberg

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