@CHIP-RTOS C Library - RTOS API
Get system time resolved to microseconds.
unsigned long RTX_GetTick_us (void);
- System time in microseconds
- This function converts the high resolution system time data
collected by the RTX_GetFineTick
API to microseconds and returns this
unsigned long 32 bit count value.
Note that this count rolls over to zero after each 2**32 microseconds
of operation, which is about 71.582 minutes.
If the RTX_FineTickInit
API has not been called, then this call will be made here one
time. (This initialization function is also called if the
lower power mode
of operation has been changed.)
Making this additional API call is time consuming and
results in the interrupts being enabled. Therefore calling
RTX_FineTickInit prior to
using this API may be advisable for time critical applications.
Once this initialization has been handled by the
API function is then suitable
for use within an Interrupt Service Routine. Interrupts are masked
here and then restored to their state on entry. Note that no call
into the @Chip-RTOS API is required by this API following
the initialization step.
Refer to RTX_GetFineTick
description for more details.
If the system's real-time interrupt has been
for kHz rates
which do not divide into 1000 an integral number of
times, then this API is inaccurate due to fixed point arithmetic
truncation problems and therefore should not be used. The problem
arises with the _us_per_RTI
constant used here,
_us_per_RTI = 1000 / _RTI_kHz
So for RTI rates like 15 kHz this integer arithmetic truncates
and the results from this API are not accurate.
The following RTI settings allow this API to function:
[1, 2, 4, 5, 8, 10, 20, 25, 40, 50]
Any RTI settings from the following set will cause this
API to not work properly
[3, 6, 12, 15, 16, 24, 30, 32, 48]
- After RTX_FineTickInit
has been invoked a single time, this library function
makes no entry into the RTOS.
- RTX API Overview
Supported since or modified in @CHIP-RTOS version
Supported by @CHIP-RTOS C Library since version
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