P9.15 has pull conflict (Bug #155)
P9.15 is connected to two pins of the am335x:
- pin 16 / gpio 1.16 / pwm 1 trip
- pin 34 / gpio 2.00 / mmc 2 cmd / emu 4
By default however the former has internal pull-down while the latter has internal pull-up. The result is an intermediate voltage level (around 1.2 V iirc), which is generally not appreciated by digital inputs and may negatively affect power consumption and possibly even lifetime.
My suggestion would be to change pin 16 to pull-up in u-boot.