Some forum users noticed that `sm.exec()` took longer the more was present
on the flash filesystem connected to the RP2040. They traced this back to
the `array` import inside `asm_pio()`, which is causing MicroPython to scan
the filesystem.
uarray is a built-in module, so importing it shouldn't require scanning the
filesystem.
We avoid moving the import to the top-level in order to keep the namespace
clean; we don't want to accidentally expose `rp2.array`.
This commit adds a new port "rp2" which targets the new Raspberry Pi RP2040
microcontroller.
The build system uses pure cmake (with a small Makefile wrapper for
convenience). The USB driver is TinyUSB, and there is a machine module
with most of the standard classes implemented. Some examples are provided
in the examples/rp2/ directory.
Work done in collaboration with Graham Sanderson.
Signed-off-by: Damien George <damien@micropython.org>
