I have an application which requires 20 digital outputs so I soldered a 20-pin IDC connector next to the double row expansion connector (J406) on a shield protoboard. I wrote a simple loop which toggles pins 22 through 53 from HIGH to LOW and discovered that pins 48-50 would only reach 3.3 volts and that pin 53 was fixed at 5 volts. I could find nothing in the literature that precludes using those pins for normal digital IO, but then I am a newcomer to the ShieldBuddy universe so I probably overlooked something. Can somebody help me out?
I can live with the 3.3 volt outputs as this is still a logic high in the 5 volt world. I have two additional ShieldBuddys on order and when these arrive I will test Pin53 to see if I get the same results. The first board may be defective or my test may be faulty.