I usually use Arduino as the default choice for all my projects thanks to all libraries available, in specifics cases, I switch to STM32 to get power computing power or peripherals the ATMega328 is not able to provide. More and more projects need ST’s micro-controllers so it is time to switch to more modern µC: I recently designed a new all-around board based on STM32L0, but all STM32 with the same package should work.

Requirements

• Breakout all I/Os
• WS2812 RGB led: blinky things, you know!
• 3.3V LDO regulator
• Easy way to select Vin or Vusb (jumper)
• Easy way to select BOOT0 (jumper)
• USB connector and ESD protection
• 200 to 300 mA mosfet to control more power or other voltages
• Reset button
• Breadboard friendly
• “FDTI” pinout connector for serial communications, and to try ST serial bootloader
• All components on one side, so the board can be easily reflowed with hotplate

Caveats & improvements

The batch of WS2812b I have works well @3.3V, but it might not be the case for all LEDs as the datasheet specifies Vin=[3.5;5V]. Also, old habits die hard, I tried to put too many things on a small board, so routing can be improved, and for the next revision I will change :

• Smaller ST-Link header (1.27 vs pogo-pin ?)
• FTDI connector can be dropped:
• Thanks to ST-Link and cheap Nucleo the serial bootloader is not used for development, I think that it might be useful in production but during development having access to the debugger is really better.
• Serial communications can be handled by the STM’s USB, if included in selected µC. If not, just wire the serial pins.
• As ST-Link is always used to program the board, BOOT0 can be tied to the ground or only be a solder bridge.
• I will not switch from Vin to Vusb really often, so this jumper can be converted to a solder bridge too.
• R6 and R7 can be taken away from each other, to ease hand soldering.
• Mounting holes are not usable with screws, only push-fit pins.

Links

• Design files and example codes can be found on Github
• Can be ordered from OSH Park