This board is centered around an STM32L412CB, which has a Cortex-M4 running at 80 MHz, 128K of flash, 40K of RAM, single precision FPU, USB FS Device, and a typical set of other peripherals.

The board is somewhat compatible with the STM32 Nucleo-32 boards, which are somewhat compatible with Arduino Nano. This is mainly so that I can use the Nano terminal blocks (https://www.amazon.com/gp/product/B095XVVGQ8).

The main purpose of the board is as a voltage/current logger for the study of battery charge/discharge curves. For this reason it has a large current sensing resistor connected to the L412’s op amp.

Another unique feature, for a board this size, is that it has an ETM Trace connector. This board works nicely with Segger’s J-Trace probe and Ozone debugger to provide instruction trace. The L412/L422 is the only STM32 Cortex-M4 (as far as I know) that has trace in a package smaller than 100 pins.

The KiCad schematic and pcb files are included in the download. All the parts are available from Digikey.

As of this writing I am bringing up basic software. I am also working on an update of the board to fix a couple minor bugs. I have not tried out the analog stuff yet.

I recommend Nefastor’s USB tutorial and STM32_VCP library:
https://nefastor.com/microcontrollers/stm32/usb/stm32cube-usb-device-library/usb-fundamentals/ https://github.com/Nefastor-Online/STM32_VCP

I followed the steps, wrote a little bit of my own code, and now I can use the L412’s native USB port as a virtual serial console, providing printf and getchar.