Does not power up when powering through the FeatherWing
This may happen on some M4 based Feathers when used with the Rev A version of the RGB Matrix FeatherWing that has a 100K pull up resistor on the enable (EN) pin. It can be solved by either replacing the 100K resistor with or adding a 10K resistor on top of it. You can even use a through hole resistor if you want.
