Talk:STM32 Core: Module Specifications

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What I've found out so far

  • It uses the STM32F103CBT6 chip, as used on the Maple Mini (
  • There are two buttons and an LED. The button on the board edge is a reset, the other button (between the reset button and the USB micro connector) is used to start the STM32's built-in ROM bootloader.
  • Normally, there's also Maple bootloader in the flash which lets you load programs using the USB DFU protocol. The Maple IDE will expect to use this.
  • The IDE can't automatically reset the Core to upload new sketches. You need to do the following:
    • In the IDE, hit the 'upload' button, and watch the messages
    • It will compile the sketch, then will wait on 'searching for DFU device'
    • As soon as you see this, hit the reset button
    • Hopefully, the IDE will see the USB DFU device when the bootloader runs briefly after reset.
  • If things get really screwed, you may need to reload the Maple bootloader. To do this:
    • Plug a Microduino FT232 board onto the bottom of the core module
    • Plug the FT232 board into your USB host, so it powers both boards and appears as a regular (FTDI) serial port e.g. COM6
    • Hold down the "ROM bootloader" button, press & release the reset button, then release the bootloader button.
    • The STM32's ROM bootloader should now be running and awaiting instructions from the serial port.
    • Get & install ST's Flash Loader app ( to read and write the core's flash.
  • As far as I can tell, the Microduino Core's STM32F103 isn't wired up the same as the STM32F103 on Maple or Maple Mini, meaning the D0-D13 pins (etc) won't work as intended in sketches if you've selected Maple or Maple Mini in the IDE 'Boards' menu.
    • For instance, the on-board LED is wired to the Core's PA8 line - this comes out as digital pin 6 when using "Maple R3" settings, and pin 25 when using "Maple Mini" settings.
    • Presumably there's a board support package somewhere with a boards.txt and settings for pin numbers which gets this working. I don't know where this is at the minute.

Cheers IH 04:14, 28 November 2014 (CST)

Pinout table

This table was worked out by tracing out the STM32 pins using a multimeter, and is not based on any official schematic. It may, therefore, contain errors, so use at your own risk!

Cheers IH