The page details how to fix common problems that can occur when using pyControl. If you encounter a problem that is not covered on this page, please post in the discussions.

Viewing logged errors

Relevant information to your problem may have been logged to an 'ErrorLog.txt' file in the pyControl root folder. You can view the errors by opening the 'ErrorLog.txt' file with a text editor. Alternatively you can view the errors from within the pyControl GUI by pressing Ctrl + e or selecting View→Error log from the menu bar.

The docs are wrong

If the docs (hosted here on readthedocs) don't seem to match your experience with pyControl, it may be that you are using a different version of pyControl from the one shown by default in the docs. You can select a different version of the docs using the dropdown menu in the bottom right. By default, the docs show the latest official release. You can get the documentation for the development branch (where new features are developed prior to being officially released) by selecting the dev version of the docs, or select versions for older numbered releases of pyControl.

Can't open GUI

To open the GUI you need to run the file pyControl_GUI.pyw using Python. One way to do this is to set the file association for .pyw files to Python 3 so that you can run the file by double-clicking it. Alternatively you can open a command prompt, change directory to the folder containing and run the file with the command python pyControl_GUI.pyw.

If the GUI does not open this is probably because you do not have the required dependencies installed, a file will be generated in the pyControl root folder called 'ErrorLog.txt' specifying which dependency is missing.

If the GUI does not run and no 'ErrorLog.txt' file is generated, try running the GUI from the command prompt (as described above) so you can see any error message generated.

Board does not show up in GUI

If no pyboards that you connect to the computer show up in the GUI's board select dropdown menu, the problem may be caused by the computers operating system language being set to something other than English. This changes the name that pyboards are given in the computers list of connected serial devices, which is used by the GUI to identify connected boards. There are two possible ways to fix this problem:

  • Use the MicroPython USB drivers rather than the generic Windows USB serial device drivers. This should ensure that pyboards are listed by the computers operating system as Pyboard irrespective of the operating system language. Information on how to install the MicroPython USB drivers is provided below in section Installing MicroPython USB drivers.

  • Alternatively, change the computers operating system language to English.

Can't connect to acquisition board

If the GUI status says 'Connection Failed' when you try to connect to the board, reset the board using the Reset button on the breakout board or MicroPython microcontroller, then try connecting again.

Can't transfer files to pyboard

If you get a message saying Error: Unable to transfer file this usually means that the filesystem on the pyboard has got corrupted. To fix this problem, reset the filesystem by following the instructions here.

The instructions say to use the Reset and USR buttons and LEDs on the MicroPython board for the file system reset. Depending on how the pyControl breakout board is mounted it may be hard to access these. However, the Reset and USR buttons on the front of pyControl breakout board 1.2 have identical functionality to those on the pyboard, and indicator LEDs 3 and 4 from the left on the breakout board have the same behaviour as the orange and green LEDs on the pyboard, so the filesystem can be reset with access only to the front of the breakout board.

After the filesystem reset has finished, reset the board again using the Reset button, then connect to the board with the GUI. The filesystem reset removes both the pyControl framework and any hardware definition from the pyboard, so you will have to reload them using the board config menu.

To reduce the likelihood of filesystem corruption, it is strongly recommended to disable the pyboards filesystem from acting as a USB flash drive before loading the framework. This can be done using the 'Disable USB flash drive' option in the board config menu.

Out of memory

If you get a message saying MemoryError: memory allocation failed either when you upload a task or while a task is running, this indicates that the pyboard has run out RAM memory. You may be able to free up a bit more memory by reloading the pyControl framework using the board config menu, as this will delete any device driver files than are not currently being used. If that is not sufficient you will need to edit your task file to reduce the memory it needs. Some things to check for are:

  • Are you storing information on the pyboard that you do not need to keep there (e.g. by appending data to a list on each trial)? If so, modify your task code so that only information needed by the task is retained on the pyboard, and information needed only for later analysis is output to the computer using print statements.
  • Does your task file combine multiple different training stages in a single file? This can lead to long and complex task files in which only a fraction of the code is actually used in any given session. Splitting different training stages into different task files can shorten and simplify the code to avoid memory issues.

Board acting funny

If a board is acting strangely, e.g. giving error messages like PyboardError('could not exec command') or pyControl Framework:Import error try the following steps to fix the problem:

  • Disconnect from the board using the GUI and reset it using the Reset button either on the pyboard or on the pyControl breakout board.

  • If resetting the board does not solve the problem, it is possible the pyboard's filesystem has got corrupted. Follow the instructions above under Can't transfer files to pyboard to reset the pyboard filesystem.

These two steps will solve the great majority of board misbehavior. If you continue to have reliability problems:

  • Make sure you have disabled the pyboard from acting as a USB flash drive using the 'Disable USB flash drive' option in the board config menu. This stops the computers from trying to access or modify the boards file system which can otherwise cause reliability issues.

  • Use the MicroPython USB drivers rather than the generic Windows USB serial device drivers (see below).

  • If the version of MicroPython running on the pyboard is <1.9 (version number is printed when the GUI connects to the board), update MicroPython.

Devices not working

If you are able to connect to the board and run example tasks that do not use external devices (e.g. or, but tasks that use external devices connected to the breakout board do not work, a possible reason is that the breakout board is not powered correctly and hence is not providing power to the devices. The breakout board needs to be powered using a 12V DC power supply plugged into the barrel socket. For suitable power supplies see the useful parts list.

Installing MicroPython USB drivers

By default, Windows will use generic USB serial device drivers for connected pyboards. Normally this works fine, but if you are having reliability problems, or the GUI is not recognising connected pyboards due the computers operating system language being set to something other than English (see above), it is recommended to use the MicroPython USB drivers.

To check which drivers you are using, look in the Windows device manager under Ports (COM & LPT), if your pyboard shows up as a USB Serial Device then you are using the generic Windows driver, if it shows up as a Pyboard USB Comm port you are using the MicroPython USB drivers. For information on installing the microputhon USB drivers see MicroPython windows setup and the MicroPython docs. The MicroPython drivers are unsigned so to install them on Windows 10, follow the instructions here under Install Unsigned Drivers from Advanced Boot Menu. You should only need to do this the first time you install the drivers on a computer.

The MicroPython USB driver is stored on the pyboards flash drive, so if you have disabled the pyboard from acting as a flash drive using the GUI's board config menu, you will need to re-enable it in order to access the driver file from Windows.

Unable to set up state machine

If you get a message saying Error: Unable to setup state machine when you upload a task, this usually means that there is a problem with the task definition file which gives an error when it is imported. The error message will be followed by a traceback saying the line in the task file where the error occurred and what the error was. Task definition files are renamed when they are transferred to the pyboard, so the traceback will refer to errors in the task definition file using this name.

Error during framework run

If you get a message saying Error during framework run while the framework is running, this usually indicates there is a problem with the task file that does not prevent the file being imported but only occurs while the task is running. This is often due to errors in state behaviour functions which only occur when the function is called. The error message will include a traceback indicating the line number in the task file where the error occurred and what the error was.

Updating MicroPython

MicroPython boards (pyboards) need to be running MicroPython version 1.9 (released May 2017) or later. When you connect to a pyboard with the GUI, the MicroPython version installed on the board is displayed. You can update MicroPython by doing the following (Windows):

  1. Download and install the software DfuSe demo.
  2. Download the latest numbered release of the firmware (e.g. v1.10) from the MicroPython download page. Note, there are two different versions of the pyboard microcontroller, PYBv1.0 and PYBv1.1, which require different versions of the firmware. The board version will be printed on the microcontroller, make sure to download the matching version of the firmware. There are various different versions of the firmware for each board with names like standard and double FP - download the standard version.
  3. Open the pyControl GUI and connect to your board. Open the Config menu and select the option Device firmware update (DFU) mode. The pyControl GUI will put the board in DFU mode and disconnect from it.
  4. Open the program DfuSe demo, in the Available DFU Devices drop down menu it should say STM Device in DFU Mode, indicating it has found the board and it is in DFU mode. In the Upgrade or Verify Action box, press the button Choose, then select the MicroPython firmware file you downloaded.
  5. Press Upgrade and then Yes in the dialog box. DfuSe demo will upload the new firmware to the board. When you see a message saying Upgrade successful, quit DfuSe demo.
  6. Press the reset button on the pyboard to exit DFU mode. Connect to the board using the pyControl GUI and the MicroPython version should be updated.

For information about updating MicroPython on Linux/Mac see here.