Flash Motherboard

Flash Marlin onto the motherboard.

With the frame complete it is time to configure the software side of things before hooking up the motherboard to the machine. This procedure was designed for Windows but it should work as well for macOS and Linux.

Necessary Components

  • Index Frame
  • Index Mobo
  • USB-A / USB-C cable (depending on MOBO revision)


  1. Download the latest Marlin firmware and unzip it

  2. Install VSCode and its PlatformIO extension

  3. Open Marlin firmware’s folder on VSCode

  4. Grab Marlin configuration files (this and this) and replace the files on Marlin/Marlin folder with those new ones

  5. Attach the Index Mobo to your computer with the USB-A cable

  6. Boot the STM32 in DFU Mode

    1. Press and hold BOOT0
    2. Press Reset
    3. Release Reset
    4. Release BOOT0
  7. Upload firmware to the board:

    Upload firmware via PIO

  8. Wait for the process to finish:

    PIO firmware upload done

  9. Press Reset on the board. Now it should show up as a COM/Serial Port on your PC:


STM32 shows up as a COM/Serial Port


STM32 shows up on lsusb

Troubleshooting DFU Upload:

  • Make sure, that your board shows up correctly in DFU mode:


STM32 in DFU mode in Device Manager


STM32 in DFU mode in lsusb

  • If the upload through VS Code does not work but the device is connected properly, edit the PIO config file (platformio.ini, located in the project folder):
  1. Create a backup of the config file
  2. Search for “STM32F407VE_black” and replace the existing section with the following:
# STM32F407VET6 with RAMPS-like shield
# 'Black' STM32F407VET6 board - https://wiki.stm32duino.com/index.php?title=STM32F407
# Shield - https://github.com/jmz52/Hardware
platform          = ${common_stm32.platform}
extends           = common_stm32
board             = blackSTM32F407VET6
# upload_port       = 0483:df11
upload_protocol   = dfu
upload_command    = dfu-util -a 0 -s 0x08000000:leave -D "$SOURCE"
board_build.f_cpu = 12000000L
build_flags       = ${common_stm32.build_flags}
  ; -D USBCON 
   -D USBD_VID=0x0483
   -D USBD_PID=0x5740

extra_scripts     = ${common.extra_scripts}
lib_ignore        = SoftwareSerial

Notice that upload_port = 0483:df11 is commented out. This setting caused issues, at least for some users. After disabling it, uploading via PIO worked.

Things to check if the board doesn’t show up as “STM32 BOOTLOADER”:

  • Check if the USB hub works by connecting devices to other ports. This is not an absolute guarantee that the connection to the STM32 works though.
  • Check if all solder joints look fine
  • Check if all necessary voltages are present (Mobo input voltage, 5V rail and 3.3V rail)
  • Keep in mind that a blank STM32 should still appear as a USB device, even if it has no firmware loaded onto it
  • Check the 8MHz crystal oscillator of the SMT32. Its correct operation is important for DFU. Wrong frequency and / or incorrect load capacitors can cause issues. Use an oscilloscope to probe the signal. You should see a smooth sine wave with stable frequency.

Alternative method to upload:

This method requires an ST-Link (V2 Clone or equivalent). Additionally you need the software STM32CubeProgrammer by ST. This method is a bit more involved and takes longer than just using the DFU mode.

  1. Compile (build) the project normally with PIO

  2. This generates a .bin-file that contains the firmware

  3. Connect your board to your ST-Link through the SWD header on board

  4. Start STM32CubeProgrammer

  5. Connect to the MCU:

    Connecting to the STM programmer

  6. Click on Open file and navigate to the firmware.bin file in PROJECT_DIRECTORY/.pio/build/STM32F407VE_black

    Opening the compiled firmware file

  7. Click on Download. This will flash the SMT32F4 with the provided firmware

    Downloading (flashing) the firmware

  8. Done! Now you just have to disconnect the ST-Link and press Reset on the board (img/firmware_download_done.png" alt=“Firmware flashing success” >}}

Configure OpenPnP

Duration: 00:00

Necessary Components

Get Software (Windows)

  1. Download OpenPNP 2.0
Last modified September 23, 2021: Typo (210509bf)