Edit: 2019-06-13: v12, now with SD card FAT file system support
Edit: 2019-05-23: v11, fixes a typo in the buffered serial code that could cause characters to get stuck repeating
Edit: 2019-05-22: updated to v10, with buffered serial using another COG
Edit: 2019-05-21: updated to v9, with VGA on pins 48-55 and USB keyboard on pins 16-24 (via garryj's single COG USB keyboard/mouse driver).
Edit: 2019-05-16: updated to v8, with 192K RAM available now and some minor REPL improvements
Edit: 2019-04-04: updated to v7 with more user RAM available (128K now, was 32K before)
Edit: 2019-03-24: updated to v6, with long integer support (so all 32 bits of smartpin registers are accessible), and support for floating point and math functions
Edit: 2019-03-19: updated to v5, with improved counters and some performance tuning. There are two versions of the interpreter, upython.binary and upython_emu.binary. Both run at 160 MHz and communicate at 230_400 baud. Internally they have very different implementations; upython.binary runs on a JIT compiled RISCV emulator which should generally be much faster, but there may be some circumstances where the cache it uses starts to thrash, and then the plain emulator upython_emu.binary might be faster. Also bugs in one hopefully won't appear in the other, but you never know
Edit: 2019-03-18: updated to v4, fixed pin reading an access to Pin(0)
Edit: 2019-03-15: updated to v3, now has a few smart pin functions implemented; docs still in README.txt
Here's a very simple MicroPython interpreter running on the P2 Eval board. Directions are in README.txt. Only one set of P2 functions are provided (in the pyb module) to turn pins on and off.