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By Mark Russinovich

An unknown device isn’t just unknown — it’s not functioning until you install the right driver. Windows can identify most devices and download drivers for them automatically. When this process fails — or if you disable automatic driver downloads — you’ll have to identify the device and hunt the driver down on your own. You should see an open port named 'USB Serial Port' Right click on the 'USB Serial Port' and choose the 'Update Driver Software' option. Next, choose the 'Browse my computer for Driver software' option. Finally, select the driver file named 'FTDI USB Drivers', located in the 'Drivers' folder of the Arduino Software download. Virtual COM Port Driver is available in the Standard and PRO editions, so you can choose the optimal set of features that is perfectly suited to your needs. Standard version Virtual Serial Port Driver is designed to provide your system with an unlimited number of virtual serial port pairs that work like real hardware COM interfaces and fully.

Published: January 12, 2012

Download Portmon(226 KB)
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Introduction

Portmon is a utility that monitors and displays all serial andparallel port activity on a system. It has advanced filtering and searchcapabilities that make it a powerful tool for exploring the way Windowsworks, seeing how applications use ports, or tracking down problems insystem or application configurations.

Portmon 3.x

Version 3.x of Portmon marks the introduction of a number of powerfulfeatures.

• Remote monitoring: Capture kernel-mode and/or Win32 debug outputfrom any computer accessible via TCP/IP - even across the Internet.You can monitor multiple remote computers simultaneously. Portmonwill even install its client software itself if you are running iton a Windows NT/2K system and are capturing from another WindowsNT/2K system in the same Network Neighborhood.
• Most-recent-filter lists:Portmon has been extended withpowerful filtering capabilities and it remembers your most recentfilter selections, with an interface that makes it easy to reselectthem.
• Clipboard copy: Select multiple lines in the output window andcopy their contents to the clipboard.
• Highlighting: Highlight debug output that matches yourhighlighting filter, and even customize the highlighting colors.
• Log-to-file: Write debug output to a file as its being captured.
• Printing: Print all or part of captured debug output to aprinter.
• One-file payload:Portmon is now implemented as one file.

The on-line help-file describes all these features, and more, in detail.

Installation and Use

Simply execute the Portmon program file (portmon.exe) and Portmonwill immediately start capturing debug output. To run Portmon onWindows 95 you must get the WinSock2update from Microsoft. Notethat if you run Portmon on Windows NT/2K portmon.exe must be locatedon a non-network drive and you must have administrative privilege.Menus, hot-keys, or toolbar buttons can be used to clear the window,save the monitored data to a file, search output, change the windowfont, and more. The on-line help describes all of Portmon's features.

Portmon understands all serial and parallel port I/O control (IOCTLs)commands and will display them along with interesting informationregarding their associated parameters. For read and write requestsPortmon displays the first several dozen bytes of the buffer, using'.' to represent non-printable characters. The Show Hex menu option letsyou toggle between ASCII and raw hex output of buffer data.

How it Works: WinNT

The Portmon GUI is responsible for identifying serial and parallelports. It does so by enumerating the serial ports that are configuredunder HKEY_LOCAL_MACHINEHardwareDeviceMapSerialComm and theparallel ports defined underHKEY_LOCAL_MACHINEHardwareDeviceMapParallel Ports. These keyscontain the mappings between serial and parallel port device names andthe Win32-accessible names.

When you select a port to monitor, Portmon sends a request to itsdevice driver that includes the NT name (e.g. deviceserial0) thatyou are interested in. The driver uses standard filtering APIs to attachits own filter device object to the target device object. First, it usesZwCreateFile to open the target device. Then it translates thehandle it receives back from ZwCreateFile to a device objectpointer. After creating its own filter device object that matches thecharacteristics of the target, the driver callsIoAttachDeviceByPointer to establish the filter. From that point onthe Portmon driver will see all requests aimed at the target device.

Portmon has built-in knowledge of all standard serial and parallelport IOCTLs, which are the primary way that applications and driversconfigure and read status information from ports. The IOCTLs are definedin the DDK file ddksrccommincntddser.h andddksrccommincntddpar.h, and some are documented in the DDK.

How it Works: Windows 95 and 98

On Windows 95 and 98, the Portmon GUI relies on a dynamically loadedVxD to capture serial and parallel activity. The Windows VCOMM (VirtualCommunications) device driver serves as the interface to parallel andserial devices, so applications that access ports indirectly use itsservices. The Portmon VxD uses standard VxD service hooking tointercept all accesses to VCOMM's functions. Like its NT device driver,Portmon's VxD interprets requests to display them in a friendlyformat. On Windows 95 and 98 Portmon monitors all ports so there is noport selection like on NT.

Download Portmon(226 KB)

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This content relates to a deprecated version of Mbed

Mbed 2 is now deprecated. For the latest version please see the Mbed OS documentation.

For the latest information about Serial, please see The Windows Serial Driver.

The mbed serial port works by default on Mac and Linux, but Windows needs a driver. These instructions explain how to setup the mbed Microcontroller to use the USB serial port on Windows.

1. Download the mbed Windows serial port driver¶

Download the installer to your PC, e.g. your desktop.

2. Run the installer¶

With your mbed plugged in, and no explorer drive windows open, run the installer:

Download Flowline Port Devices Drivers

It will take some time (especially on Vista), and pop up a few 'unsigned driver' warnings, but after a while you should have a Serial port.

Where Next¶

Download Flowline Port Devices Driver Printer

• SerialPC - Communication with a PC
• Terminals - Guide to using terminal applications

Troubleshooting

If you have multiple mbed microcontrollers, but the serial port only appears for one of them:

• Make sure you run the installer for every mbed; windows loads the driver based on the serial number, so it needs to be run for each mbed you use

If the installer fails because 'No mbed Microcontrollers were found':

• Check your mbed Microcontroller is plugged in

If the installer reports the message 'mbedWinSerial_nnnnn.exe is not a valid Win32 application':

• It is likely you are using Internet Explorer to download the installer file, which sometimes seems to only download part of the installer application for an unknown reason
• To solve this, download the installer with a different browser (Firefox, Chrome), and try again; this should solve the issue.

If the Installer appears to hang:

• Check if windows has popped-up a 'unsigned driver/permission' window; these often get hidden behind other windows with nothing to indicate so in the taskbar! Windows may be waiting for you to click 'OK'!

If you have any problems, or think this tutorial could be improved, please tell us in the Forum!