Hi all,
I am working on improving nRF51 emulation. Specifically I want to implement the
special "System OFF" mode. System OFF is a power saving mode. In this mode, the
system can only be woken up by a reset or a handful of peripherals (most
notably, GPIO via high/low level detection on configured pins). System reset is
triggered upon wakeup.
I've been digging into the QEMU mailing list and source code and have come to
the conclusion that deep sleep and low power modes are not implemented. There
seems to be support for turning off ARM CPU cores, e.g. as used by imx6_src.c.
But that doesn't apply here because I only have one CPU.
So ultimately what I think I will try to implement is what the nRF51 reference
manual calls "Emulated System OFF mode". From the reference manual:
If the device is in debug interface mode, System OFF will be emulated to
secure
that all required resources needed for debugging are available during
System OFF...
Since the CPU is kept on in emulated System OFF mode, it is recommended
to add an infinite loop directly after entering System OFF, to prevent the
CPU from
executing code that normally should not be executed.
Does anyone have any guidance on how to implement this? I don't particularly
care about fidelity. As long as a GPIO level trigger can break the CPU out of
the infinite loop (which the reference manual tells users to add) and jump into
the reset vector, it will be good enough for my use. I don't really care about
masking out other interrupt sources, for example.
Thanks,
Chris
