I have the UART RX pin and another GPIO pin set to wake the MCU from shutdown when they go high.
When the board is not connected to anything and I toggle either of these two pins high, the MCU wakes from shutdown as expected.
However, when the board is on a test fixture that has a pull up on the UART RX pin, the board won't wake when the other GPIO is toggled, but does wake from the UART RX pin being toggled.
I think what's going on is that since the UART RX pin is already at the wake up level when the MCU goes into shutdown mode, it is somehow blocking all wake up signals until it is toggled low and high.
It would seem that the wake up is level based? What I would like is for the wake to be edge based, thus sitting at the high level would not assert the wake signal.
There appear to be registers that might do this (IOCFGx: IOEV_MCU_WU_EN), but I've tried enabling both the IOEV_MCU_WU_EN and EDGE_DET bits, but that didn't work.
Is it possible to wake on positive going edge and not on a level?