The MicroBlocks virtual machine is designed for 32 bit microcontrollers with at least 16Kb of RAM and 64Kb of Flash memory. The source code for the virtual machine is built using Arduino board definitions and libraries and maintained as a project (to build all VMs) using PlatformIO.
As an experiment, the virtual machine has also has been ported to run on Linux, so it can run on a Raspberry Pi. Pin I/O is not yet supported on the Raspberry Pi but we hope to add that eventually.