How to flash STM32 PlatformIO firmware using dfu-util

First, you need to find the correct firmware file. dfu-util will flash firmware.bin, not firmware.elf. You can find firmware.bin in


inside your project folder. [PROFILE_NAME] is the name of the build profile you’re using, i.e. the name of the section in platformio.ini. For example:


Now flash using dfu-util:

dfu-util -a 0 -D .pio/build/PROFILE_NAME/firmware.bin -s 0x08000000


  • -a 0. The STM32 appears as four different devices in dfu-util (see dfu-util --list): The flash, option bytes, RAM etc each appear as a separate device. We only care about the flash device, which is always the first (index 0) of those devices, at least in every board I have seen so far
  • -D [filename]Download the firmware to the device
  • -s 0x08000000: Flash at address 0x08000000 which is the address of the STM32 flash.
Posted by Uli Köhler in Embedded, PlatformIO, STM32

How to exit/reset STM32 DFU bootloader

Both dfu-util and dfu-tool can flash firmware, but their current versions can’t reset the STM32 from DFU mode to run the application.

I found that using MicroPython’s pydfu.py is able to reset the. Note that currently I use pydfu.py only for resetting, not for flashing (but that might change in the future).

Download using

wget https://raw.githubusercontent.com/micropython/micropython/master/tools/pydfu.py

Install the PyUSB dependency using

sudo pip3 install pyusb

And then reset the STM32 in DFU mode:

python3 pydfu.py -x


Posted by Uli Köhler in STM32

How to fix ‘command not found: pio’ even though PlatformIO is installed


You have installed PlatformIO on your computer using Visual Studio code, however when you try to run it in your terminal/shell, you see:

$ pio
zsh: command not found: pio


PlatformIO is installed in $HOME/.platformio, but not added to the PATH environment variable, so your terminal can’t find it. Add it using

echo "export PATH=\$PATH:/home/${USER}/.platformio/penv/bin" >> ~/.profile

and then logout from your current session and log back in again (or reboot) in order for the changes to take effect. After that, you can run pio from any shell.

Posted by Uli Köhler in Linux, PlatformIO

How to fix pio remote agent start: You are not authorized! Please log in to PlatformIO Account.


When running

pio remote agent start

you see an error message like

2021-10-05 17:37:23 [info] Name: Raspberry Pi
2021-10-05 17:37:23 [info] Connecting to PlatformIO Remote Development Cloud                                                                    
2021-10-05 17:37:23 [info] Successfully connected
2021-10-05 17:37:23 [info] Authenticating
2021-10-05 17:37:23 [error] You are not authorized! Please log in to PlatformIO Account.                                                        
2021-10-05 17:37:23 [info] Successfully disconnected


You need to login to your PlatformIO account. Run

pio account login

which will prompt you for your username & password. If you don’t have an account, register using

pio account register
Posted by Uli Köhler in PlatformIO

How to fix pio remote agent start: error: can’t find Rust compiler


When running pio remote agent start, while PlatformIO installs the Python packages, you see an error log like

  generating cffi module 'build/temp.linux-armv7l-3.7/_openssl.c'                                                                                                           
  creating build/temp.linux-armv7l-3.7                                                                                                                                      
  running build_rust                                                                                                                                                        
      =============================DEBUG ASSISTANCE=============================                                                                                            
      If you are seeing a compilation error please try the following steps to                                                                                               
      successfully install cryptography:                                                                                                                                    
      1) Upgrade to the latest pip and try again. This will fix errors for most                                                                                             
         users. See: https://pip.pypa.io/en/stable/installing/#upgrading-pip                                                                                                
      2) Read https://cryptography.io/en/latest/installation/ for specific                                                                                                  
         instructions for your platform.                                                                                                                                    
      3) Check our frequently asked questions for more information:                                                                                                         
      4) Ensure you have a recent Rust toolchain installed:                                                                                                                 
      Python: 3.7.3                                                                                                                                                         
      platform: Linux-5.10.60-v7l+-armv7l-with-debian-10.10                                                                                                                 
      pip: n/a                                                                                                                                                              
      setuptools: 58.2.0                                                                                                                                                    
      setuptools_rust: 0.12.1                                                                                                                                               
      =============================DEBUG ASSISTANCE=============================                                                                                            
  error: can't find Rust compiler                                                                                                                                           
  If you are using an outdated pip version, it is possible a prebuilt wheel is available for this package but pip is not able to install from it. Installing from the wheel would avoid the need for a Rust compiler.                                                                                                                                   
  To update pip, run:                                                                                                                                                       
      pip install --upgrade pip                                                                                                                                             
  and then retry package installation.                                                                                                                                      
  If you did intend to build this package from source, try installing a Rust compiler from your system package manager and ensure it is on the PATH during installation. Alternatively, rustup (available at https://rustup.rs) is the recommended way to download and update the Rust compiler toolchain.                                              
  This package requires Rust >=1.41.0.                                                                                                                                      
  ERROR: Failed building wheel for cryptography
Successfully built pyopenssl
Failed to build cryptography
ERROR: Could not build wheels for cryptography which use PEP 517 and cannot be installed directly
Error: Traceback (most recent call last):
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/platformio/package/manager/core.py", line 127, in inject_contrib_pysite                                       
    from OpenSSL import SSL                                                                                                                                                 
  File "/home/pi/.platformio/packages/contrib-pysite/OpenSSL/__init__.py", line 8, in <module>                                                                              
  File "/home/pi/.platformio/packages/contrib-pysite/OpenSSL/crypto.py", line 12, in <module>                                                                               
  File "/home/pi/.platformio/packages/contrib-pysite/cryptography/x509/__init__.py", line 8, in <module>                                                                    
  File "/home/pi/.platformio/packages/contrib-pysite/cryptography/x509/base.py", line 18, in <module>                                                                       
  File "/home/pi/.platformio/packages/contrib-pysite/cryptography/x509/extensions.py", line 20, in <module>                                                                 
  File "/home/pi/.platformio/packages/contrib-pysite/cryptography/hazmat/primitives/constant_time.py", line 11, in <module>                                                 
ImportError: /home/pi/.platformio/packages/contrib-pysite/cryptography/hazmat/bindings/_constant_time.abi3.so: cannot open shared object file: No such file or directory    

During handling of the above exception, another exception occurred:                                                                                                         

Traceback (most recent call last):                                                                                                                                          
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/platformio/__main__.py", line 115, in main                                                                    
    cli()  # pylint: disable=no-value-for-parameter                                                                                                                         
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/core.py", line 1137, in __call__                                                                        
    return self.main(*args, **kwargs)                                                                                                                                       
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/core.py", line 1062, in main                                                                            
    rv = self.invoke(ctx)                                                                                                                                                   
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/platformio/commands/__init__.py", line 44, in invoke                                                          
    return super(PlatformioCLI, self).invoke(ctx)                                                                                                                           
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/core.py", line 1668, in invoke                                                                          
    return _process_result(sub_ctx.command.invoke(sub_ctx))                                                                                                                 
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/core.py", line 1665, in invoke                                                                          
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/core.py", line 1404, in invoke                                                                          
    return ctx.invoke(self.callback, **ctx.params)                                                                                                                          
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/core.py", line 763, in invoke                                                                           
    return __callback(*args, **kwargs)                                                                                                                                      
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/click/decorators.py", line 26, in new_func                                                                    
    return f(get_current_context(), *args, **kwargs)                                                                                                                        
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/platformio/commands/remote/command.py", line 40, in cli                                                       
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/platformio/package/manager/core.py", line 129, in inject_contrib_pysite                                       
  File "/home/pi/.platformio/penv/lib/python3.7/site-packages/platformio/package/manager/core.py", line 156, in build_contrib_pysite_package
    subprocess.check_call(args + [dep])
  File "/usr/lib/python3.7/subprocess.py", line 347, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/home/pi/.platformio/penv/bin/python', '-m', 'pip', 'install', '--no-compile', '-t', '/home/pi/.platformio/packages/contrib-pysite', '--no-binary', ':all:', 'pyopenssl >= 16.0.0']' returned non-zero exit status 1.


An unexpected error occurred. Further steps:

* Verify that you have the latest version of PlatformIO using
  `pip install -U platformio` command

* Try to find answer in FAQ Troubleshooting section

* Report this problem to the developers



You need to install rust using

sudo apt -y install rustc

and then run the original command again:

pio remote agent start


Posted by Uli Köhler in PlatformIO

What is the correct supply voltage for DALI?

DALI operates at a supply voltage of 16V, current limited at 250mA.

Since the specified voltage range for a 1 bit is between 9.5V and 22.5V, the supply voltage can also be in this range (with 16V being right in the middle of this range. But even if you technically can use a 12V supply, this might not work for setups with longer cable lengths and/or setups with many DALI devices connected. If you have a 12V or 5V power supply, I recommend to use a boost converter to generate 16V.

Note that you always need to current-limit the DALI supply. Just connecting a power supply to the DALI line could destroy your equipment.

Posted by Uli Köhler in Electronics

How to install PlatformIO remote agent on Raspberry Pi

This is from the Super Quick installation procedure from the official PlatformIO documentation:

python3 -c "$(curl -fsSL https://raw.githubusercontent.com/platformio/platformio/master/scripts/get-platformio.py)"
sudo apt -y install rustc libffi-dev
echo "export PATH=\$PATH:/home/${USER}/.platformio/penv/bin" >> ~/.profile

Run it as user (whatever user you want to use PlatformIO as – by default, this is the pi user) and not as root!

After running these commands, log out and log back in again in order for the changes to the PATH environment variable to take effect.

After that, run

pio remote agent start

to complete the installation procedure. This will take quite some time.

After logging in, you can use pio from the shell:

$ pio

Usage: pio [OPTIONS] COMMAND [ARGS]...

  --version          Show the version and exit.
  -f, --force        DEPRECATE
  -c, --caller TEXT  Caller ID (service)
  --no-ansi          Do not print ANSI control characters
  -h, --help         Show this message and exit.

  access    Manage resource access
  account   Manage PlatformIO account
  boards    Embedded board explorer
  check     Static code analysis
  ci        Continuous integration
  debug     Unified debugger
  device    Device manager & serial/socket monitor
  home      GUI to manage PlatformIO
  lib       Library manager
  org       Manage organizations
  package   Package manager
  platform  Platform manager
  project   Project manager
  remote    Remote development
  run       Run project targets (build, upload, clean, etc.)
  settings  Manage system settings
  system    Miscellaneous system commands
  team      Manage organization teams
  test      Unit testing
  update    Update installed platforms, packages and libraries
  upgrade   Upgrade PlatformIO to the latest version


Posted by Uli Köhler in PlatformIO, Raspberry Pi

How to flash Marlin on BigTreeTech Octopus V1 using debug adapter

In order to flash the Bigtreetech Octopus V1 using my STLinkv2 debug adapter, I needed. First we need to note that the first 32k of flash memory are occupied by the bootloader (0x08000000 to 0x08008000). So we need to flash the firmware at address 0x08008000. By default, this is not configured correctly in Marlin.

Open ini/stm32f4.ini and edit the [env:BIGTREE_OCTOPUS_V1]:

platform           = ${common_stm32.platform}
extends            = stm32_variant
board              = marlin_BigTree_Octopus_v1
board_build.offset = 0x8000
board_upload.offset_address = 0x08008000
build_flags        = ${stm32_variant.build_flags}
                     -DSTM32F446_5VX -DUSE_USB_HS_IN_FS
upload_protocol = stlink

Note that you absolutely need to re-flash the bootloader in case you accidentally flashed with the old configuration. Follow the official documentation in order to flash the bootloader. I flash usin STM32CubeProgrammer 2.7.0 (2.8.0 does not work) on both Linux and Windows.

The [env:BIGTREE_OCTOPUS_V1_USB] will be updated automatically as it includes [env:BIGTREE_OCTOPUS_V1]

Posted by Uli Köhler in 3D printing, Electronics, STM32

ESP32 JTAG pinout

The ESP32 uses the following pins for JTAG:

  • GPIO12: TDI
  • GPIO13: TCK
  • GPIO14: TMS
  • GPIO15: TDO

Source: ESP32 reference manual, section 4.10 IO_MUX Pad List

Posted by Uli Köhler in ESP8266/ESP32

Is your PD device 802.3bt PoE++ Type-3 or Type-4?

Note: Do NOT confuse Type-3 or Type-4 with PoE class 3 and class 4!

If your PD uses a maximum of 51W (class 1-6 – up to 60W at the PSE), your device is Type 3. If your device uses 62W or 71.3W (class 7 or 8 – 75W or 90W at the PSE), your device is Type 4.

In case your device uses more than 71.3W (or 90W at the PSE), your use-case is not covered by IEEE 802.3bt aka PoE++.

Note that “uses” does not refer to the actual power draw of your device but whatever class you present during the PoE classification process. Typically, this is configured using a resistor, depending on your PoE PD controller.

For reference, see this Ethernet Alliance Whitepaper

Posted by Uli Köhler in Electronics, Networking, PoE

What is the default PlatformIO / Arduino ESP32 TIMER_BASE_CLK?

On PlatformIO / Arduino, by default the TIMER_BASE_CLK is 80 MHz (the maximum frequency the ESP32 can run at).

If you want to verify this yourself, use this firmware:

#include <Arduino.h>

void setup() {

void loop() {


Posted by Uli Köhler in Arduino, Electronics, Embedded, ESP8266/ESP32, PlatformIO

How to fix PlatformIO serial monitor scrambled output


When using the Monitor function of platformIO, you see strange characters instead of strings being printed, for example:



This issue almost always appears due to the Monitor function using the wrong UART speed. You can see from the log in our screenshot above:

--- Miniterm on /dev/ttyUSB0  9600,8,N,1 ---

that PlatformIO is using 9600 baud in this case – but your microcontroller is sending data at a faster speed (or, rarely at a slower speed).

Most firmwares using serial IO use 115200 baud, so that’s what I’d recommend to try first, but if that doesn’t work, look out for config options named baud rate or similar, or for lines of code like


in the firmware.

In order to change the Monitor UART speed, open platformio.ini and add

monitor_speed = 115200

Full platformio.ini example for ESP32:

platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200

After that, restart the Monitor function.

Posted by Uli Köhler in Arduino, Electronics, Embedded, ESP8266/ESP32, PlatformIO, STM32

How to fix ESP32 PlatformIO error: ‘LED_BUILTIN’ was not declared in this scope


When trying to compile your ESP32 firmware using PlatformIO, you see this error message:

src/main.cpp: In function 'void setup()':
src/main.cpp:22:13: error: 'LED_BUILTIN' was not declared in this scope
     pinMode(LED_BUILTIN, OUTPUT);


Important: Some ESP32 boards such as the ESP32-DevKitC have no builtin LED at all ! Either connect an external LED or find another method of doing whatever you are intending to do.

On most ESP32 boards that do have a builtin LED, the LED is connected to pin 2 – however, PlatformIO does not define LED_BUILTIN p. In order to fix the issue, define LED_BUILTIN yourself by using

#define LED_BUILTIN 2

at the top of every file where you see this error.

Posted by Uli Köhler in Electronics, Embedded, ESP8266/ESP32, PlatformIO

How to fix Linux ESP32 PlatformIO PermissionError: [Errno 13] Permission denied: ‘/dev/ttyUSB0’


When trying to flash a ESP8266 or ESP32 board on Linux, you see an error message like

Warning! Please install `99-platformio-udev.rules`. 
More details: https://docs.platformio.org/page/faq.html#platformio-udev-rules

Auto-detected: /dev/ttyUSB0
Uploading .pio/build/esp32dev/firmware.bin
esptool.py v3.1
Serial port /dev/ttyUSB0
Traceback (most recent call last):
  File "/home/uli/.platformio/penv/lib/python3.8/site-packages/serial/serialposix.py", line 322, in open
    self.fd = os.open(self.portstr, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
PermissionError: [Errno 13] Permission denied: '/dev/ttyUSB0'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/uli/.platformio/packages/tool-esptoolpy/esptool.py", line 4582, in <module>
  File "/home/uli/.platformio/packages/tool-esptoolpy/esptool.py", line 4575, in _main
  File "/home/uli/.platformio/packages/tool-esptoolpy/esptool.py", line 4074, in main
    esp = esp or get_default_connected_device(ser_list, port=args.port, connect_attempts=args.connect_attempts,
  File "/home/uli/.platformio/packages/tool-esptoolpy/esptool.py", line 120, in get_default_connected_device
    _esp = chip_class(each_port, initial_baud, trace)
  File "/home/uli/.platformio/packages/tool-esptoolpy/esptool.py", line 313, in __init__
    self._port = serial.serial_for_url(port)
  File "/home/uli/.platformio/penv/lib/python3.8/site-packages/serial/__init__.py", line 90, in serial_for_url
  File "/home/uli/.platformio/penv/lib/python3.8/site-packages/serial/serialposix.py", line 325, in open
    raise SerialException(msg.errno, "could not open port {}: {}".format(self._port, msg))
serial.serialutil.SerialException: [Errno 13] could not open port /dev/ttyUSB0: [Errno 13] Permission denied: '/dev/ttyUSB0'


As described at the top of the error message, install the PlatformIO udev rules:

curl -fsSL https://raw.githubusercontent.com/platformio/platformio-core/master/scripts/99-platformio-udev.rules | sudo tee /etc/udev/rules.d/99-platformio-udev.rules

then restart udev:

sudo systemctl restart udev

After that, unplug an re-plug your ESP32 board in order for the changes to take effect

Additionally, I recommend adding your user to the dialout group – the Linux group that owns most USB devices:

sudo usermod -a -G dialout $USER

In order for the changes to take effect, log out from your current session completely and log back in again (or reboot). While not strictly neccessary in order to fix this specific error message, it helps in preventing future USB permission issues.

Posted by Uli Köhler in Electronics, Embedded, ESP8266/ESP32, PlatformIO