STM32 Explorer Board - STM32XP

This is an educational development board conceived as part of a PCB Design course. The course is offered via Portal Embarcados website (Course Page). The hardware and firmware project source files can be found in the following repository: MechatronixLab/STM32XP.

License

This is an open source hardware project licensed under CERN-OHL-P. More details on license file.

Board specifications

The board is based on the STM32F411, more specifically, the STM32F411RET6. Additionally, the board features some components commonly used in Embedded Systems, such as:

• DC-DC Converters
• OLED Display, connected to the MCU via I²C
• RGB LEDs
• Audio buzzer, controlled via PWM
• External ADC with analog antialiasing filters
• USB 1.1 Full Speed via a Type-C connector
• Micro SD Card for easy data storage, connected to the MCU via SPI
• Input buttons
• Several I/O pins routed to breakout connectors/pins
• CR2032 Battery for RTC operation

Tests

Some more photos and videos of the board working can be found on my Instagram profile @MechatronixLab.

Known bugs

DC-DC output voltage adjustment

After manufacturing the first batch, I've found 2 minor errors in the design. The most critical is that resistors R2 and R3 had incorrect values (this is noted in red n page 2 of the schematic):

You can replace R2 with 1.8k and R3 with 10k, then it will work correctly. If assembled as in the original BOM, the power supply output will be lower than expected, but no damage will occur.

Eliminating buzzer noise

In the original design, there might be some noise in the buzzer while handling the board. That is because a resistor is missing to connect the gate of the buzzer MOSFET driver to ground. This will be fixed in a later revision. An improvised solution may be to add a resistor from the gate and scraping the copper fill to reveal a ground connection, as shown below: