STM32duino - Blue Pill F103C8

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


USB Fix

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 like shown here:
http://wiki.stm32duino.com/index.php?title=Blue_Pill#Hardware_installation
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


Schematic

Here one find the schematic.
Pinout:


Specification

 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

Software