One of the first aspects that we can note is the presence of many contacts on card’s border, including the now famous female contacts connector compatible with the Arduino shield. Externally, however, two double strips of male contacts (one per side) are what STM calls “Morpho” pinout, used on other STM development boards.
In figure Arduino pinout is shown in purple, while the Morpho pinout is in blue: notice how all Arduino pins are remapped exactly on Morpho inner pin strip (connectors CN7 and CN10): this allows us to always have access to Arduino pinout also once a shield is plugged on the board. This helps us to debug software easily and to use those outputs when some shields don’t pass-through.
NUCLEO board connectors’ pinout
CN7 and CN10 connectors pins are not connected to Arduino compatible connector and they provide other proprietary I/O or power connector typical of STM32 microcontrollers. This allows the card to be used in other projects which require greater connectivity.
There is more; CN7 and CN10 Morpho connectors are replicated also on the board backside (always with male contacts strips), allowing you to mount the NUCLEO board on another board that could be seen as a new shield and that can access (also and not only) to Arduino pinout.
Another interesting feature is the presence on the NUCLEO board of a PCB area that is always part of the board, but serves exclusively to its programming and debugging. It is the PCB part, looking in figure, that is close to the two small buttons and that can easily be physically split; this helps reducing the NUCLEO board size that actually runs the applications.
Layout of the NUCLEO board.
This portion of the circuit is independent from the rest and is always equipped with a STM32 microcontroller suitably programmed during manufacture to manage the functions of a real programmer and debugger for the STM8 and STM32 family of microcontrollers.