🛠 Découvrir la Blue Pill : que trouve-t-on dans la boîte ?

One board, one chip, a lot of history

The "Blue Pill" is an unbranded Chinese development board based on the STMicroelectronics STM32F103C8T6 microcontroller, an ARM Cortex-M3 running at up to 72 MHz. The STM32F1 series, announced by ST in June 2007, was the first STM32 family; the official ST product page is titled "STM32F103 — Arm Cortex-M3 Microcontrollers (MCU) 72 MHz". The board itself measures 23 mm × 53 mm (blue PCB, hence the name), and its nickname comes from a post on the STM32duino forum, referencing the Matrix movie.

What's on the board

• Memory: 64 KB of flash and 20 KB of SRAM for the C8T6 (boards may be populated with C6 32 KB, C8 64 KB, or CB 128 KB — the chip marking is not reliable).
• Connectors: 2 rows of 20 pins at 2.54 mm pitch (PA0–PA7, PA11–PA15, PB0–PB15, PC13–PC15, VBAT, NRST, 3V3, 5V, GND), a micro-USB connector, a 4-pin SWD connector (3V3/PA13/PA14/GND), a reset button, and BOOT0/BOOT1 jumpers (BOOT1 on PB2).
• Arduino Nano compatible footprint: Nano expansion boards plug in directly… but the logic is 3.3 V, not 5 V.
• Clocks: 8 MHz HSE crystal and 32.768 kHz LSE RTC crystal.
• No radio connectivity: no WiFi, no Bluetooth, no Ethernet. USB is device-only, full-speed (PA11/PA12).

Three beginner pitfalls

1. The user LED on PC13 is sink-mode: it is wired between VCC and the pin, so it lights up when the pin is LOW. A classic "blink" code written with HIGH/OFF seems to do nothing.
2. No power protection: the +5V pin is directly connected to the USB connector's +5V. Never power the board via USB and an external source simultaneously.
3. Endemic counterfeits: most Blue Pills sold today contain counterfeit STM32s or pin-compatible clones (e.g., GigaDevice GD32F103). This is not a dealbreaker, but you need to know about it (see the diagnostic tutorial).

Read next

The reference schematic and the complete pinout table are on stm32-base.org; the ST product page and the RM0008 reference manual complete the official documentation.