<i>try reading the SoC spec for the A20. If you can find it.</i><p>Googling &quot;AllWinner A20 datasheet&quot; brings in good results.<p>&quot;Broadcom BCM2836 datasheet&quot; doesn&#x27;t. All you get is part of the GPIO registers, and absolutely NO electrical specifications. (Part of me really wants someone working there to &quot;take one for the community&quot; and leak the full datasheet. Ironically, that&#x27;s how the AllWinner docs were originally released.)