STM32 Nucleo-F411RE and MicroPython Getting Started

These instructions build the firmware and uses the .hex file to flash to the board using the ST-Link on the board and the ST-Link Utility, no hardware hacking required. These instructions may also work with the following Nucleo 64 boards (ST reference: MB1136):

• Nucleo-F091RC
• Nucleo-F401RE
• Nucleo-F411RE (obviously) (Tested and working)
• Nucleo-F446RE
• Nucleo-L073RZ
• Nucleo-L452RE
• Nucleo-L476RG
• And possibly others found in the /micropython/ports/stm32/boards direrectory which is explained later on.

This guide assumes a basic general knowledge of computers, programming, software issue handling, working with Electronics and microcontrollers. I will shorten microcontroller to MCU.

Index for this README/Guide

Software Requirements
Get the Board Ready
Build the Firmware
Donwload the Firmware
Test MicroPython
Upload Python Files
Useful Links
Pinouts
Contributing

Software Requirements

Most of the other guides on the Internet explains how to program and flash the MicroPython on a Linux based development system. This made it difficult for me to get it working on a Windows based system, hence Why I made this guide to help other people who wants to get started on a Windows based environment.
The specific environment this was tested on was Windows 10 Enterprise 64 Bit.

Many of the other guides also shows how to upload by bypassing the ST-Link on the Nucleo board. This is because the ST-Link on the Nucleo board actually connects serially to the MCU and not using USB as in the boards like the Adafruit Feather etc. The Adafruit Feather and many other boards has a onboard USB port which when you connect via the micro USB connector to your PC, it will actually show a "drive" which is a portion of the flash memory of the MCU. This is why in these cases you can see the boot.py , main.py and other micropython files directly on the MCU in these cases versus NOT in the Nucleo-F411RE case.

The following software is required and needs to be downloaded and installed, if not already:

1. Python version 3.4 or later (I tested with version 3.8.1)
2. STM32 ST-Link Utility (Mine was version 4.5.0)
3. Arm-none-eabi-gcc development environment (I used version 10.1.0)
4. MinGW, I am not sure which version it was, the installer downloaded the newest version. Just download the newest version. This is used to run the make utility so you could use another building package as well, something like CMake.
5. Adafruit's ampy tool.
6. The MicroPython repository, I got version 1.13-46-g85f2b239d at the time of doing this.

I really did not do any research on which versions to use with what versions. I just used the most recent versions I could find and install if it was not already installed on my computer.
I do however recommend to use stable release versions for obvious reasons.

Install Python

1. Head over to python.org the official Python website.
2. There is a Download menu option, as soon as you hover over it, it will bring up a submenu and a panel with the download for your system.
3. Click on the button and it will download the Python installation executable. Install Python by going through the prompts. I usually prefer to install it in a directory directly under my c: drive and I name this directory "Python", thus under c:\Python.
4. Make sure to select the add Python to path. If you forgot, just add the installlation directory under your Environment Variable PATH Variables.
5. you can now open a command prompt and type python --version or py --version and it should return the Python version for you. When you type python or py and enter you will get the REPL Python Interpreter.

Install the ST-Link Utility

1. Go to the ST Microelectronics website and search for ST-Link Utility, click on the STSW-LINK004 product link and download the utility by clicking on the "Get Software" link.
2. Note that you will need to register for a ST site user account which is free and does not take too long.
3. Exctract and run the installer which will install the utility as well as some device drivers which will be used when connecting via USB to the STLink boards.
4. When you are done there should be a new shortcut on your desktop STM32 ST-Link Utility.

Install the Arm-none-eabi-gcc toolchain

Note that other versions of the Arm-none-eabi-gcc toolchain would also be acceptable to install if preferred.

1. Download the toolchain from the Bleeding-Edge-Toolchain download site, the link that I got was this one which will start a download of a *.7z archive, mine had the name "arm-none-eabi-gcc-10.1.0-200517-win64".

You may need to install a unzip utility which can unpack 7Z compressed files, I use the 7-Zip utility which is small and free

2. Extract the files and then copy it over to a suitble directory. I copied it into my _e:\dev directory underneath the name "arm-none-eabi-gcc-10.1.0-200517-win64". Make sure there is no spaces in any of these directories. (This is also a good practise for any mcu related development) The directory will look like this:
3. Add the following two directories to your path (depending on where you installed the toolchain)

• E:\dev\arm-none-eabi-gcc-10.1.0-200517-win64
• E:\dev\arm-none-eabi-gcc-10.1.0-200517-win64\bin

How to add Environment Variable PATH entries
4. Open a new command prompt and test by typing arm-non-eabi-gcc --version and you should see the version number, if not, your environment path variable did not take effect.

Install MinGW

You can also install or use another type of build utility like Ninja Build

1. Go to the MinGW website and at the top right, click on the "Downloads" link.
2. Just abovee the "Download Package List" there is a executable that you can download for Windows. Click on that to download the executable. (mingw-get-setup.exe)
   
3. Run this executable and follow the prompts to install the MinGW envioronment.
4. I installed it under c:\MinGW which will end up looking like this:
   

Install Adafruit Ampy tool

1. Open up a new command prompt window.
2. Type pip install adafruit-ampy
3. This will install the ampy toolset on your system.
4. Type ampy --help to test if the installation was successful.

Obviously you would need Python to be installed first before doing these steps.

Install the MicroPython Repository

1. Go to the MicroPython Github Repository and download the entire repository.
   You can do this by cloning it with git if you know how or by downloading it as a zip file by clicking on the green button and then the "download zip".
   
2. Extract it to a directory of your choice, I extracted it to e:/dev/micropython which looks like this:
   

Special NB!

1. Go to your Python installation directory and make a copy of python.exe, name it python3.exe . This is an important steps for us Windows users. The firmware will not build because it is looking for a python3 executable which exists normally on Linux, but not on Windows.
   

All the required software will now be installed.

It is also recommended that you get some sort of terminal program which will be used later on to access the REPL on the MCU, it is however not a prerequisite to be able to get your files onto the MCU, but nice to test. In the older days Wondws had the Hyper Terminal, but you can also use PuTTY or TeraTerm or any other terminal program that you know or prefer to use.

How To Add Environment Variables PATH entries

1. Click on the start button (or press the Windows key) then start to type Environment Variables on the windows menu the Environment variables links will appear like this:
   
2. Click on the Edit the System Environment Variables link on the start menu.
3. The systems properties window will appear, at the bottom, click on the _Environment Variables... button.
   
4. Select the Path under System variables then click on Edit.
   
5. Add a directory to the path by clicking on the New button and pasting the directory just like the exampples already in the list. When done you can close all the dialogs.
   

Getting The Board Ready

You will need:

• The Nucleo-F411RE development board.
• A micro USB cable connected to a USB port on your computer.

1. Make sure all jumpers is set to their default settings on the board. Thus CN2 must have two jumpers next to one another (NUCLEO), JP6 (IDD) must have a jumper and JP5 must have a jumper towards the U5V side. No other jumpers or pins need to be "jumped" or connected. (Only at the bottom there are two jumpers on either side, these are just palce holders and you can use these two jumpers if you need jumpers)
   
2. Connect the micro USB cable to the board and see that the board power up, two or more LEDs will lit up and your computer will install the device drivers then open up a "thumb drive" via explorer. If this happens then you have connection.

Build the Firmware

1. On your computer using file explorer, go to the MinGW installation folder c:\MinGW on my computer. Then go to the msys\1.0 sub directory.
   
2. Double click on the msys.bat file to open up a Bash Command Window.
3. In this Bash window, change your directory to the micropython directory, cd e:/dev/micropython

Note that in Bash the directory seperator is different direction from the standard command prompt "/" instead of "".

4. Now type make -C mpy-cross It will build some files and then it will finish with an error, My experience is to ignore this error, everything works with this error.
   
   
   

5. Change directory to the STM32 sub directory cd ports/STM32

6. Now type make submodules
   

Steps 4 and 6 only have to be performed once when you install micropython, thereafter only the required MCU board is build when needed.

7. Now we can build the required firmware by typing make BOARD=NUCLEO_F411RE
   
   
   
8. The firmware is now built and a directory containing all the files can be found under the e:\dev\micropython\ports\stm32\ directory. This will be named as build-NUCLEO_F411RE
9. You can now close/exit the Bash window.

Donwload the Firmware

1. With your board connected to your computer via the micro USB cable, open up the ST-Link Utility.
2. In the menu, click on Target then Connect
   
3. Go to File then Open File and select the firmware.hex file.
4. Click on Target then Program and Verify then click on the Start button.
   
5. The Nucleo-F411RE is now programmed and the ST-Link LED will falsh fast. You can now disconnect the device from ST-Link Utility and clos it. Then safely remove the USB drive then unplug and replug the board.
   

Congratulations! MicroPython is now loaded onto the Nucleo-F411RE board.
Lets test it now.

Test MicroPython

1. Connect your board then open up your favorite Terminal Program and setup your serial connection as follow:

   • Com port: Usually something higher, just look, you will identify it easily.
   • 115200, 8 bit, no parity, 1 stop bit, no flow control.
     
     

2. You will now be presented with the Python REPL interpreter.
   

3. If it does not show you the interpreter like above, then you will have to reset the device by following these steps:

   • First with board powered on and cable connected and terminal program connected as above, press both the User (blue) and Reset (black) swithes and hold.
   • Now release the Reset switch. The green LED will flash once then a pause then flash twice then a pause then flash three times then a pause and then the sequence will repeat. When the thrid flash ends, at that moment release the blue switch too.
   • The Green LED will then give about four quick flashes then goes off.
   • The REPL should now be visible in your terminal program.

4. We can now test if Python is working by trying out some common Python oneliners.

   • 1 + 1 then Enter should give the integer two in the next line.
   • print('Hello') then Enter should give the string Hello in the next line.
   • more elaborate example:

   from pyb import LED
   led = LED(1)
   led.toggle()
   led.off()
   led.on()
   

   • 

5. If all that worked you should have seen the LED goes on and off as we do some of the commands. Congrats, this means Python is working on our MCU.

Upload Python Files

1. Create a project directory where you will add your main.py and boot.py files.

2. Create a file called main.py and edit the file with the following code which will be our blink the user LED code:

   from pyb import LED
   import time
   
   led = LED(1)
   
   while True:
       led.toggle()
       time.sleep(1)

3. Open up command prompt and change dirtectory to this project directory. Your board should still be connected and powered on.

4. Remembering the previous COM port number, type the following ampy -p COM11 ls (Just use the right com port number) This should return /flash which means that the main.py and boot.py is under the /flash directory on the MCU "drive".

5. If you type ampy -p COM11 get main.py it will print out the contents of the main.py file (the default one at this stage) on the MCU.

6. Now we upload our edited main.py by typing the following command ampy -p COM11 put main.py The user LED will flash fast as the file is uploaded. You can now press the Reset button to restart the board and run the user code.

7. The green user LED will now flash at a rate of one second on and one second off.
   

Congratulations! We have written our first program which is now running.

The MicroPython documents is really helpful to get you started, be sure to check it out on the MicroPython website.

Useful Links

STM32 Nucleo Basic User Manual
MicroPython - Github Repository
MicroPython - Documents Online
Pre-Compiled DFU firmware Files
Bleeding Edge Arm Toolchain
Safe mode and factory reset
MicroPython Forums
Alternate way to load MicroPython
Library pyb, the class Pin
MicroPython vs CircuitPython plus Great links

Pinouts

FAQ

1. Why do I not see the main.py, boot.py and other default MicroPython files in the drive when I connect the board?
   A: The drive that you see with the files is the MBED storage on the ST-Link onboard programmer and NOT the MCU flash. Other development boards like the Arduino Feather exposes the USB from the MCU which maps the flash memory where you can see these files, but not on this Nucleo-F411RE board.

2. Cats or Dogs?
   Dogs, always...

End

This guide was made available for free by me. You are welcome to get in contact with me to fix errors, update, add or change something to this guide.
roanfourie@gmail.com