Andy Brown designed a development board for the STM32F042 in the TSSOP20 package:
Development board features
- USB. The 042 series supports USB and although 32Kb is not a lot of space to include a USB driver and your application logic it does make sense to hook up those USB data lines and thereby enable USB device development.
- Switching regulator. All the development boards that I’ve seen seem to use a low dropout regulator (LDO) to supply power to the MCU which means that they’re unable to supply much current to any peripherals that you’re prototyping. The discovery boards warn you not to draw more than 100mA and many of the 3rd party boards use one of the 1117 regulators which, with up to a 1A limit, look great on paper but the universally chosen SOT-223 package will burn up in smoke long before you get anywhere near that figure.
- VDDA control.The discovery boards allow you to supply VDDA externally if required. I’d like to keep this ability.
- Onboard 8MHz crystal. All the F0 series can be clocked from the internal high speed internal (HSI) 8MHz oscillator with an option to use an external 8Mhz crystal. I’ll include such a crystal on my board.
- Onboard NPN transistor. I often need to use an NPN transistor as a low-side switch to control a load either requires too much current to power from a GPIO or is running from a different voltage level (e.g. 5V). I’ll include a simple transistor on this board configured ready to function as a switch.
- A LED. Because, well, you know, blinky.
Project info at Andy Brown’s blog.
Check out the video after the break.