fire_interrupt function should be used for events in the past. As we have now
64bit timestamp, we can figure out what is in the past, and ask a target to invoke
an interrupt immediately. The previous attemps in the target HAL tickers were not ideal, as it can wrap around easily (16 or 32 bit counters). This new
functionality should solve this problem.
set_interrupt for tickers in HAL code should not handle anything but the next match interrupt. If it was in the past is handled by the upper layer.
It is possible that we are setting next event to the close future, so once it is set it is already in the past. Therefore we add a check after set interrupt to verify it is in future.
If it is not, we fire interrupt immediately. This results in
two events - first one immediate, correct one. The second one might be scheduled in far future (almost entire ticker range),
that should be discarded.
The specification for the fire_interrupts are:
- should set pending bit for the ticker interrupt (as soon as possible),
the event we are scheduling is already in the past, and we do not want to skip
any events
- no arguments are provided, neither return value, not needed
- ticker should be initialized prior calling this function (no need to check if it is already initialized)
All our targets provide this new functionality, removing old misleading if (timestamp is in the past) checks.
Depending on families, different HAL macros are defined to check the
state of serial interrupts. In several cases, we can find only 1 macro:
__HAL_UART_GET_IT_SOURCE
Checks whether the specified UART interrupt has occurred or not
But in F0, F3, F7, L0, L4 there are 2 different macros
__HAL_UART_GET_IT
Checks whether the specified UART interrupt has occurred or not
__HAL_UART_GET_IT_SOURCE
Checks whether the specified UART interrupt source is enabled.
In the later case, __HAL_UART_GET_IT_SOURCE was being used so far,
but actually needs to be replaced by __HAL_UART_GET_IT. Using the right
macro, we also check the proper flags accordingly.
The symbol Systick_Handler was defined as a weak symbol in us_ticker.c and
startup_nRF51822.s. While it work as expected when an application is compiled
from mbed OS source code it creates a duplicate symbol issue when mbed OS is
bundled as a library.