The datasheet for TM4C123GH6PM (spms376b) suggests that SysTick can deliver regular ticks unaffected by sleep transitions if its clock source is selected to be PIOSC (div 4). If deep sleep clock is chosen to be PI, then this seems to hold. However, if the deep sleep clock is chosen to be LFI, then the ticks seem to slow down (by a very large factor). So, SysTick doesn't seem to fix the problem of changing clock source across sleep that the general-purpose timers suffer from. Is this by design?
I've counted on SysTick to get a clock that's stable across sleep states. I've written a SysTick wrapper-module in SYSBIOS and "ported" Clock to be able to use it; only to find the above. Last hope is the timer Hibernation module.
Test app that isolates the two cases:
https://github.com/alexeicolin/tivaapps/blob/systick-and-sleep/app_systick.c
The output with PI sleep clock is hundreds of 'Alarms' per second. Output with LFI sleep clock is a trickle couple of 'Alarms' per tens of seconds. Expecting the two cases to have the same output.
