Quote:
Originally Posted by mmatej
Thanks for the karma! I think it could not be used as input port (also, I am not going to try it - there is currently no easy HW "unbrick"). While I was playing with the port, I've also tried to connect it to the piezo speaker and no way it could power speaker directly (even a piezo). I almost couldn't hear it (and with increasing freq -> decreasing volume).
Maybe next time.
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Piezo earphones can be heard quite loudly driven by a germanium diode (1N34A or quivalent, as used in old "crystal set radios"). Perhaps your piezo speaker element wants 5 volts?
I would think that anything that can power an LED could surely drive earphones.
Also, piezo "speakers" are very frequency sensitive, with a small range of resonant frequencies. They work great as "beepers", but are very poor for general sound output. I would use cheap (dollar store) headphones or earbuds for testing...
EDIT: You were probably driving the piezo speaker at a frequency too low for it. They are not good at delivering low frequencies from such a small surface area (unless you use many of them in a phased array). They are GREAT at ultrasonic frequencies though.