Can use Vin, but the reverse polarity diode that is between the barrel jack and Vin is only rated for 1A, and you get less than that because the board itself uses some of that 1A.
Can use Vin, but the reverse polarity diode that is between the barrel jack and Vin is only rated for 1A, and you get less than that because the board itself uses some of that 1A.