CPU Time
The MyNewt cputime module provides high resolution time and timer support.
Description
The cputime API provides high resolution time and timer support. The module must be initialized, using the os_cputime_init() function, with the clock frequency to use. The module uses the hal_timer API, defined in hal/hal_timer.h, to access the hardware timers. It uses the hardware timer number specified by the OS_CPUTIME_TIMER_NUM system configuration setting.
Data Structures
The module uses the following data structures:
uint32_tto representcputime. Only the lower 32 bits of a 64 timer are used.struct hal_timerto represent a cputime timer.
List of Functions
The functions available in cputime are:
| Function | Description |
|---|---|
| os_cputime_delay_nsecs | Delays for a specified number of nanoseconds. |
| os_cputime_delay_ticks | Delays for a specified number of ticks. |
| os_cputime_delay_usecs | Delays for a specified number of microseconds. |
| os_cputime_get32 | Gets the current value of the cpu time. |
| os_cputime_init | Initializes the cputime module. |
| os_cputime_nsecs_to_ticks | Converts the specified number of nanoseconds to number of ticks. |
| os_cputime_ticks_to_nsecs | Converts the specified number of ticks to number of nanoseconds. |
| os_cputime_ticks_to_usecs | Converts the specified number of ticks to number of microseconds. |
| os_cputime_timer_init | Initializes a timer. |
| os_cputime_timer_relative | Sets a timer to expire in the specified number of microseconds from the current time. |
| os_cputime_timer_start | Sets a timer to expire at the specified cputime. |
| os_cputime_timer_stop | Stops a timer from running. |
| os_cputime_usecs_to_ticks | Converts the specified number of microseconds to number of ticks. |
List of Macros
These macros should be used to evaluate the time with respect to each other.
CPUIME_LT(t1,t2)-- evaluates to true if t1 is before t2 in time.CPUTIME_GT(t1,t2)-- evaluates to true if t1 is after t2 in timeCPUTIME_LEQ(t1,t2)-- evaluates to true if t1 is on or before t2 in time.CPUTIME_GEQ(t1,t2)-- evaluates to true if t1 is on or after t2 in time.