Getting started with VCP mode under Windows

VCP icon with a tutorial icon merged togetherThe majority of Dracal Technologies' precision sensors can be delivered with the VCP mode: Virtual COM Port option. This option allows the instrument to communicate by serial COM protocol in addition to the default USB protocol. The commands available in VCP mode are available in the following documentation: Access Data from your VCP (Virtual COM Port) Dracal Sensors. The present documentation is intended as a complementary tool to guide users step-by-step through the process of getting their Dracal VCP instruments up and running on Windows.


Disclaimer: This documentation offers one possible avenue of use and in no way claims to be the only, or the best, of all possible options.

Windows Users

1 Installation

When you receive your sensor supporting the VCP option, it is in "USB" mode. The first step to get your instrument up and running is to download the DracalView software, which includes all of our command-line tools in addition to the graphical interface.

2. Navigate in the DracalView directory

When you download the software, the default directory where the software is downloaded is: C:\Program Files (x86)\DracalView. To use the command-line tools, you must open a terminal and navigate in this directory. Dracal Technologies has provided a tool called "command-line tools" that you can call from your search bar and which, when you click on it, will open a terminal already positioned in the right place:



3. Switch from USB to VCP mode

The communication protocol of the VCP-series products is changed from USB to VCP mode via our command-line tool dracal-usb-set. To do this, the set_protocol VCP conversion command must first be executed, followed by the disconnection of the instrument. In the following example, the disconnection of the instrument was performed virtually via the reset command available with dracal-usb-set:

C:\Program Files (x86)\DracalView>  dracal-usb-set -s E16026 set_protocol VCP
C:\Program Files (x86)\DracalView>  dracal-usb-set -s E16026 reset

If only one Dracal instrument is connected to your computer at the time these commands are executed, you can omit specifying the serial number of your instrument (since there is only one) by using the -f option as in the following example:

C:\Program Files (x86)\DracalView>  dracal-usb-set -f set_protocol VCP
C:\Program Files (x86)\DracalView>  dracal-usb-set -f reset

Notes for Windows users: Upon execution of the reset command, the following echo will be returned in your terminal tool:

C:\Program Files (x86)\DracalView>  dracal-usb-set -f reset
USB control message error: usb_control_msg: sending control message failed, win error: The device does not recognize the command.

This behavior is normal and confirms that the disconnection has been successfully completed.

Once switched to VCP mode, all DracalView software tools (GUI and command-line tools) will no longer be able to communicate with your Dracal instrument. This is a particularity of the Windows operating system that imposes this constraint, as it does not allow a device to communicate in multiple languages. This constraint does not exist under Mac OS and Linux.

4. Find the COM identifier of your sensor

Use your Windows search bar to access your "device manager". In this window, navigate to the "Ports (COM & LPT)" section. In the image below, for example, the connected Dracal sensor is identified as "COM3":


5. Communicating with the instrument while in VCP mode - Configuring PuTTY

As neither DracalView nor the command-line tools allow us to interacts with the instrument once it is in VCP mode, we will use PuTTY as a communication intermediary. You can download it here: and follow the default installation steps. After installing it, you should have access to it through your search window:


To access the device data, we will create a new profile in PuTTY with "Serial" as the connection type. Then, in the "Serial line" field, we will enter the name of our device, having been previously identified as COM3 in this example. It is recommended that you immediately save the session by giving it a name, such as "Dracal COM" for example:




Before querying the instrument, we need to make other configurations.

Under "Terminal", we disable the echo by checking "Force off" in both options under "Line discipline options". Then, under "Connection->Serial", we deactivate the "Flow control" by selecting "None":


The configuration settings are complete. Go back to "Sessions" and save again:


Note: When you launch your next PuTTY session to access data from your Dracal sensors, simply select your "Dracal COM" session and click "Load". Then, you will just have to make sure to enter the correct serial identifier of the instrument in question, which will most likely have another identifier (which is COM4 in the image below for example):

You are ready to query your instrument by clicking on "Open":


A window will then open, allowing you not only to view the data returned by your instrument, but also to interact with it by calling all the commands it supports and which are documented in this section of the VCP product user guide. Among other things, calling the USB PROTOCOL command followed by the RESET command will switch your instrument from VCP mode to USB mode, allowing you to use the visualization and data acquisition tools available in the DracalView software.

Note: When calling the different commands in the terminal, although they will not be displayed in the terminal screen, they will be executed and an echo line will confirm that they have been received.

6. Logging data with PuTTY

To save the data to a file, simply navigate to "Session -> Logging". Under "Session logging:", we recommend checking the "All session output" option. Then you need to choose the name of the output file and its location in the "Log file name:" section. In the example below, we have imposed ".csv" for the output file format, otherwise PuTTY proposes a ".log" extension by default. Finally, just click on "Open":


When the window opens, we recommend that you quickly invoke the "INFO" command so that the names of the columns can be identified very quickly when the log file is opened:


Leave the window open: the file is being written to. When your data acquisition task is complete, you can simply close the PuTTY window and open the file you created.

Note: You will have to delete the first few lines of your file. If you invoked the "INFO" command as suggested, your column names will be available a few rows from the beginning of your file.

In conclusion

The Windows operating system requires users of Dracal instruments to switch between USB and VCP modes depending on whether the user wishes to use all of our data acquisition tools (USB mode) or to integrate data in VCP mode. If there are other items that you feel should be covered in this documentation, we warmly welcome your suggestions.