I am really missing option to put my Orange Pi PC Plus board to sleep and wake up using power button.
Any chance to get this feature soon?
Shallow sleep (not much peripherals turned off) might be already possible, but deeper sleep state is tricky. For that you need special firmware on coprocessor. Such firmware, crust, is in the works, but I don't plan to use it in near future. At least until needed drivers come into mainline Linux.
I'm not sure shallow sleep is really usable. It would give you feeling that you turned off the board, but power consumption wouldn't be much lower.
Anyway, someone would have to do some research on that, but I rather work on other issues, like why some H264 and HEVC videos don't work properly.