GPIO usage of HiFiBerry boards You can find the latest version of this document on our main web site. Have more questions? Submit a request Comments Georg Düsterhöft May 03, 2017 16:58 Seems to be a little outdated to me as my HifiBerry DAC+ HW 2.2 doesn't use Pin 38 at all (no connections from or to this pin). HiFiBerry team May 04, 2017 09:40 No, this is completely correct. While this pin isn't connected, you can't use it is it is part of the sound subsystem and it is reserved.