The STM32duino board is based on the ARM Cortex M3 core like the Arduino Duo. The version I use is the Blus Pill.

On Hackaday is a good article about STM32 clones: STM32-Clones - the good the bad and the ugly.

Unfortunately the board comes with a 10k pullup resistor from D+ to 3.3V (in the schematic it's a 4.7k). That can cause problems on some PCs. Just take the R10 out and replace it with an 1.5k resistor.
One might let the 10k resister untouched and just put a 1.8k in parallel. Between 3.3V and pin A1 (PA12).

And here are some useful infos about the pullup resistors on USB:
https://www.beyondlogic.org/usbnutshell/usb2.shtml
https://amitesh-singh.github.io/stm32/2017/05/27/Overcoming-wrong-pullup-in-blue-pill.html

Here is the schematic (Attribution: http://wiki.stm32duino.com.)

Pinout:

Attribution: Rasmus Friis Kjeldsen, CC BY-SA 4.0 , via Wikimedia Commons

 Model: STM32F103C8T6
 Core: ARM 32 Cortex-M3 CPU
 Debug mode: SWD
 72MHz work frequency
 64K flash memory
 20K SRAM
 2.0-3.6V power, I/O
 Reset(POR/PDR)
 8MHz crystal
 LED on pin PC13

Here is an installation guide here:
http://wiki.stm32duino.com/index.php?title=Installation
and here:
https://github.com/rogerclarkmelbourne/Arduino_STM32/wiki/Installation
Uploading a sketch:
http://wiki.stm32duino.com/index.php?title=Uploading_a_sketch
Debugging with GDB by Hackaday:
https://youtu.be/D-MbC9N5U7o

https://www.stm32duino.com/
https://www.arduinolibraries.info/architectures/stm32

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