The NRF51 doesn't have a systick. When the MCU doesn't have a systick, the
HAL has to export several functions which will be use by the kernel to
manage the tick:
* os_tick_init provides the initialization function for the alternative
hardware timer.
* os_tick_val returns the current value of the alternative hardware timer.
* os_tick_ovf returns the overflow flag of the alternative hardware timer.
* os_tick_irqack is an interrupt acknowledge function that is called to
confirm the alternative hardware timer interrupt.
The HAL should also call OS_Tick_Handler needs to be called as the
hardware timer interrupt function.
In the case of the NRF51, two RTCs are available:
* RTC0: reserved for soft device
* RTC1: used by us_ticker.
RTC1 is a 4 channels timers, channel 0 is used for us_ticker, and
in this port channel 1 is used for tick generation.
Implementation notes:
* RTC1_IRQHandler: has to be written in assembly otherwise a stack
overflow will occur because the function OS_Tick_Handler never
returns. This function is called when RTC1 channel IRQ is triggered.
* tick generation has been optimised for a tick with a duration of
1000us.
* us_ticker can still be compiled and used without RTX enabled.
More information about alternative timer as RTX Kernel Timer:
https://www.keil.com/pack/doc/CMSIS/RTX/html/_timer_tick.html
Add lock functions so that malloc and environment variable access are
thread safe. Add the compiler option "-o thread-safe" to use the full
version of newlib which is thread safe.
Note that this patch does NOT make file access thread safe.
Add the locks and flags necessary to make the IAR standard library
thread safe. These changes consist of:
-Add compiler flag "--guard_calls" to ensure C++ function-static
variables with dynamic initializers are initialized in a
thread safe manner
-Add the linker flag "--threaded_lib" so the thread safe version of
the standard library is used
-Implement mutex functions required for IAR thread safety
-Create a set of stub functions in retarget.c for when the rtos is not present
Added an #ifndef directive to the __MBED_CMSIS_RTOS_CM and __CMSIS_RTOS macro definitions in order to prevent "Incompatible redefinition of macro" warnings from the online compiler.
Vincent Coubard
Martin Kojtal
Steven Cooreman
Russ Butler
Neil Thiessen
Russ Butler
Mihail Stoyanov