I installed the board support packages for the Arduino IDE (Adafruit and dadamachines M4) and compiled and started to download the example sketch hex-lens-test. The download failed, and now the board is unresponsive; the serial port no longer appears in Tools/Ports. If I press the RST button on the board, the yellow LED flashes when I release it; that is the only sign of life. Does anybody have any suggestions about how to revive it?
A possibly related question- many of the examples contain the cryptic reference “see variant.h”. What is variant.h, and where can it be found?