There is also this post in the Announcements section about adding the G400 to TinyCLR. Re-adding G400 to TinyCLR OS It has a line that says “For help on updating the bootloader on your G400, take a look at our new docs19.” When you click on that link it goes to a 404. http://docs.ghielectronics.com/hardware/products/ucm/g400.html#loading-bootloader-version-2