Questions and answers on ROBOTICS topics

TXT 4.0 Controller / ROBO Pro Coding

How can the error that the TXT 4.0 controller cannot be connected with ROBO Pro Coding and "txtapi" is shown in the display of the TXT 4.0 controller be eliminated?

Please reinstall the TXT 4.0 controller firmware by following these instructions

ROBOTICS TXT Smart Home / ROBOTICS Sensor Station IoT

Which ROBOPro Version do I need for the TXT Smart Home kit?

Version ROBOPro 4.7.0 is required. Access to the fischertechnik Cloud no longer works with older versions. The version can be downloaded from the eLearning portal. The link can also be found in the assembly instructions included with the construction kit.

How secure is my data in the fischertechnik Cloud?

With regard to the TXT Smart Home kit we place particular importance on data security.

To this end, all data sent (both the data sent by TXT to the fischertechnik Cloud and the data transmitted from the server to the WEB browser) is transmitted encrypted with certificates (https standard, green padlock in the WEB browser).
The TXT controller is protected by a secure so-called root password against external hacker attacks as to the best possible extent.
If pictures are taken by the fischertechnik camera, this is indicated by an optical signal on the model in order to guarantee that nobody is photographed without their consent. Pictures are only taken and send if the user has logged in on the dashboard in the WEB browser with their password.
Data that the individual user saves in the cloud is protected via a personal account with password access and is only accessible to the respective user. The very secure OAuth2 Industry Standard is used for this. For personal data, fischertechnik fulfils the statutory requirements of the new EU General Data Protection Regulation in full.  
The servers on which the fischertechnik Cloud is operated are located in Germany. This guarantees that the strict European requirements for storing data are complied with.

Which internet browsers does fischertechnik Cloud work with?

Windows 7:
Chrome, Firefox, Internet Explorer 11, Internet Explorer 12

Windows 10:
Edge, Chrome,  Firefox, Internet Explorer 11, Internet Explorer 12

Windows 10 mobile

Safari, Firefox, Chrome

Firefox, Chrome

It doesn´t work with Android Samsung Internet V 7.

What security measures must be observed with the TXT controller in WLAN client mode?

(!) Safety note: TXT Controller firmware version 4.2.4 or higher (!)

Please observe the following notes if the TXT Controller is operated in the so-called WLAN client mode:

- Always activate the WLAN encryption WPA2 in the TXT WLAN settings when you connect the TXT controller in WLAN client mode to a WLAN network.
- Do not operate unknown or untrusted devices in the same wireless network with the TXT controller.
- Select WLAN keys correspondingly complex, e.g. the preset WLAN keys of the current routers
- Do not give the WLAN key to third parties

ROBO LT Beginner Set / ROBOTICS Beginner

Can programs be stored on the ROBO LT controller?

No, the ROBO LT controller can only be operated in online mode (USB connection to PC).

Can the ROBO LT controller be operated without a connection to the PC (download mode)?

No, the ROBO LT controller can only be operated in online mode (USB connection to PC).

Can the ROBO LT controller be controlled with the ROBOPro software?

Yes, that works. The ROBO interface must be set as COM/USB interface.

Can the TXT or TX controller be controlled with the ROBOPro Light software?

No. ROBOPro Light software is exclusively for the LT Controller and as of version 4.3.1 also for the BT Smart controller.


What are the system requirements for ROBOunderPro?

ROBOPro 4.2.x with the TXT controller under Windows/Mac/Linux Windows:

The current ROBOPro version runs under Windows 7, 8 and 10.


On Mac OS X, ROBOPro can be installed using the commercial program "CrossOver" and with the open source software "WineBottler" ( No additional drivers are required for the TXT controller and all interfaces (Bluetooth, USB, WLAN) are supported.
Alternatively, ROBOPro can be used when it is installed in a Windows virtual machine. In this case, USB and WLAN are supported. Please note that you need a fully-fledged Windows license.


With the help of the program wine ( ROBOPro can also be installed on Linux. For this, the following command must be executed on the console: 

msiexec -i Setup.exe.
No additional drivers are required for the TXT controller and all interfaces (Bluetooth, USB, WLAN) are supported. Ubuntu 14.04 LTS and OpenSuse 13.2 distributions were tested.

The ROBOTICS software ROBOPro does not operate correctly.

Please download the latest software version (update) under the heading Service/Downloads.

The USB driver cannot be installed - no connection to the controller can be established.

As of ROBOPro version 3.1.2, the USB driver is pre-installed and operates automatically when the TXT/TX controller is connected to the USB interface. You can download the manual here.

Error message "An unexpected situation has occurred" appears with the ROBOTICS software ROBOPro.

There is a software or programming error. Please send the program that causes the error message with a short explanation by e-mail to fischertechnik ( We're here to help!

I cannot update my TX controller’s firmware.

Start ROBOPro from the Windows start menu and not from the fischertechnik ROBOTICS terminal. Then the firmware update works without problems.

Error message "No interface to USB could be found" appears with the ROBOTICS software ROBO Pro.

Is there a power failure?
Please check whether the display on the ROBO TXT or TX controller is working or the light-emitting diode on the ROBO interface is lit.

Is the TXT/TX controller or the ROBO interface correctly connected to the computer?
Please carry out a visual inspection.

Is the USB driver installed correctly?
For the driver, see "C:\ Program Files (x86)\ROBOPro\USB Driver Installation."

Does the ROBOPro software offer a random function?

The subroutine library "Random" contains several subroutines that can be used to generate random numbers.

Where can I get a manual for C programming a ROBO interface or a TXT/TX controller?

You can download the manual for C programming under the heading Service/Downloads/ROBOTICS.

I cannot install the USB driver. I always receive an error message.

The USB driver can only be installed by a user who has administrator rights on the PC.

How can one access multiple TXT/TX controllers in ROBOPro?

You will find corresponding information in chapter 7 "Controlling Multiple Interfaces" in the ROBOPro Help. The following error messages could appear: "The minimum number of processes is too small. Please increase the maximum number of processes in the Properties window of the main program."

In the ROBOPro program's "Properties" tab, the minimum number of processes must be higher than the number of "green traffic lights" that you use in your program.

Is there a software manual for the ROBOPro software?

The ROBOPro software contains a help file, in which the programming language is explained in detail. It also contains numerous examples. In addition, all the programming elements are explained. This can be opened via the menu bar under "Help -> Help." On the ROBOPro CD this help is available as a printable PDF file, which you can download.

Where can I find the digital booklets for the ROBOTICS kits?

The digital booklets for TXT Automation Robots, TXT ElectroPneumatic and TXT Explorer are installed together with the software ROBOPro on the computer. After installation, these are available via the menu items "Windows Start-All Programs."  

The didactic accompanying material for the TXT Discovery Set is also installed together with the software ROBOPro on the PC and can be selected via the ROBOTICS terminal, which also shows the welcome movie. 

Compared to a printed version, the digital guidance material offers numerous advantages:
Under "First Steps," an animated movie shows exactly step-by-step how the controller is put into operation and how to create the first program.

The "TXT Discovery Set" contains information about components, programming the models and troubleshooting. For each model, there is a direct link to a sample program in ROBOPro. The accompanying material is also linked directly to ROBOPro's help file, so that you can jump directly to the help desk at the right places for further detailed information. 

All didactic accompanying information is available on our eLearning portal at: However, the linking of other external data (ROBOPro software, ROBOPro help, sample programs) does not work with these pdf files. To do this, the pdf files must be installed on the computer together with the ROBOPro software.

The didactic accompanying materials cannot be opened.

It could be because "Adobe Acrobat Reader" is not installed on the computer. This is available for free download at
Note: Other readers may not support all the convenient features (such as links to other files, animations) used in the accompanying materials.

The ROBOPro update to firmware 4.4.4 does not work. An error "Phase 3" is displayed.

The cause can be an antivirus program on the computer, which interferes with the update. If the antivirus program is deactivated, the update works again.

TXT/TX Controller

How can I connect an old fork light barrier 32357 to the TXT/TX controller?

Can the TX Controller be connected with ROBO Pro software in Windows 10 via Bluetooth?

Unfortunately, this is not possible. Please use the USB connection under Windows 10.

What has to be considered for the TXT firmware update 4.7.0?

Firmware version 4.6.6 must already be installed on the TXT controller. Older TXT firmware versions must first be updated to 4.6.6.

How can I measure the battery voltage with the TXT/TX controller?

Connect the battery to the TXT/TX controller's universal input (I1-I8). In this case, you must connect the battery’s negative pole to the input ground socket and connect the battery's positive terminal with the other input jack.

What is the maximum voltage allowed to operate the TX /TX controller without causing damage?

9V. We recommend the power supply with the fischertechnik Accu Set or Power Set.

Can the sound module be connected to the ROBOTICS TXT/TX controller?

Yes, connect the TXT/TX controller and the sound module to a common power source (important). Then connect a sound input A - B - C to one of the ROBO TXT/TX controller's outputs (O1 - O8).

What is the conversion rate for analog channels?

An internal time clock of 10ms is used in ROBOPro. This means that a program gets a new analog value every 10ms.

Why do I need the ROBO TXT/TX controller for the ROBO TXT Automation Robot?

The ROBO TXT Automation Robots are equipped with two encoder motors, which send fast counting pulses to the TXT/TX controller. The ROBO interface does not have fast counter inputs that can process these signals. Therefore, you need the ROBO TX or the TXT controller.

Suddenly the TXT/TX controller inputs no longer work in my ROBOPro program.

In the ROBOPro toolbar,you have mistakenly switched the programming environment from TXT/TX to ROBOIF. If you switch this environment back to TXT/TX by mouse click, the inputs are read correctly again. 

Upon updating the ROBOPro TXT controller the error message occurs: "Error Update Phase 2 (oder 3).“ What should I do?

In this case something went wrong with the update. First of all, you can try to download the update repair tool (link to the download area) from our website and run it as described there. If the update still does not work, you must send the TXT controller to us for repair. 

My TXT controller no longer boots. What can I do?

Unfortunately in this case, you must send the TXT controller to us for repair.

Under Windows 10, the driver "fischertechnik USB ROBOTICS TXT Controller (by Knobloch GmbH)" is wrongly not recognized, but the standard driver of Windows with the name "usbser.sys".

Uninstall all fischertechnik driver packages named "fischertechnik ROBOPro 64/32 bit USB Driver" under Programs and Functions under Windows 10 and then reinstall the drivers. The installation file for the TXT driver can be found in the ROBOPro installation directory under C:\Program Files (x86)\ROBOPro\USB-Treiber Installation\.

Does the TXT controller support "I2C Clock Stretching"?

Yes, from version TXT Firmware 4.2.4 this is supported.

An error message appears when updating the TXT firmware

When updating the TXT firmware, the error message appears:

-    Can not open update file on TXT Controller (transfer error)! oder
-    Can not open update file on TXT Controller (file error)!

You may have activated Autostart for a program on the TXT or a program is currently running on the TXT controller. Please exit the program before starting the update.

Does the camera work with the old TX controller?

The USB camera does not work with the old TX controller, since it does not have a USB Host port. The camera can be used with the TXT controller.

ROBO Interface

How can I determine that the Robo Interface has detected the connected I/O extension?

You can see that only the green "Ext" light-emitting diode flashes.

How many expansion modules can I connect to the ROBO interface?

The ROBO interface can control a maximum of three I/O extension modules.