I wanted to know if my CS32F103C8T6 Blue Pill boards and my RobotDyn STM32F103C8T6 board have functioning I2C capability. The answer is yes.

I tested them by using an INA219 breakout board. Mine is a clone of Adafruit INA219 breakout board. My setup was from from this tutorial from the Adafruit Learning System, with modifications:

1. Using the Blue Pill boards instead of Arduino UNO or other boards from the tutorial.
2. Using a 12V lead acid battery instead of AA cells.
3. Using a 10Ω 100W power resistor instead of an LED.

Here is the diagram of the physical setup:

For the code, I just used the getcurrent example from Adafruit INA219 library. From Arduino IDE: File → Examples → Adafruit INA219 → getcurrent. My Arduino IDE settings to upload the program to the board were:

• Board: “Generic STM32F1 series”
• Board part number: “BluePill F103C8”
• U(S)ART support: “Enabled (generic ‘Serial’)”
• USB support (if available): “CDC (generic ‘Serial’ supersede U(S)ART)”
• USB speed (if available): “Low/Full Speed”
• Optimize: “Smallest (-Os default)”
• C Runtime Library: “Newlib Nano (default)”
• Upload method: “Maple DFU Bootloader 2.0”
• Port: “/dev/ttyACM0”

After all set, I clicked the upload button in Arduino IDE. The upload was successful. Then I opened the serial monitor in Arduino IDE. What I got from all my Blue Pills boards look like this:

Bus Voltage:   11.45 V
Shunt Voltage: 97.07 mV
Load Voltage:  11.55 V
Current:       970.40 mA
Power:         11108.00 mW

Bus Voltage:   11.45 V
Shunt Voltage: 96.90 mV
Load Voltage:  11.54 V
Current:       969.40 mA
Power:         11096.00 mW

Here’s how it actually looked:

In the photo above the current shown by the multimeter was higher compared to the serial monitor output. This was because I took the photo first, then copied the serial monitor output later.

So It worked for all of my boards: two CS32F103C8T6 Blue Pill boards and one RobotDyn STM32F103C8T6 board. So both chip have functioning I2C capability. Could it be that CS32F103C8T6 are nearly identical to STM32F103C8T6? I have no idea whether China Key System, the company that produce CS32F103C8T6 chips, are actually licensed to produce Arm chips. I don’t even know if the CS32F103C8T6 that I got are genuine CKS32 or clones. Imagine that: clone of a clone. Browsing their website gave me this error page.

According to Google Translate, that means:

Your visit may be dangerous to the website and has been intercepted by Cloud Defense.

Google Translate for China Key System 403 Error

So I am unable to check anything from China Key System.

How about other clones? As far as I am aware, there are several STM32 clones, such as:

• CKS32 (China Key System)
• APM32 (Apex Microelectronics)
  Edit 2020-12-29: Gone. All mentions of APM32 disappeared from Apex Microelectronics website.
• GD32 (GigaDevice).

I’m not sure about calling GD32 as clone of STM32, I think I read somewhere that GigaDevice actually have license to produce Arm chips. No idea about the others. I found some links about these clones, some positive, some negative:

• CS32F103C8T6 datasheet and tests (was:”UNEXPECTED idcode” flashing bluepill)
• Chinese clones attack STM32 microcontrollers
• GD32F103: A STM32F103 on steroids!
  Update 2020-07-24: Roger Clark deleted this article, so here is the 2019-12-22 snapshot of the article, from the Wayback Machine by the Internet Archive.
• GD32F3 not really clone of STM32F3
• 32F103 Comparison: part 1, part2, part 3, and lastly part 4.

I am just glad that the I2C functionality doesn’t require much drama. This is plug and play, just like with Arduino boards.

Laters!