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Add precision info to time.monotonic()

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This commit is contained in:
Dan Halbert 2021-10-08 10:20:52 -04:00
parent f6681ef930
commit d0b2544f88
1 changed files with 18 additions and 3 deletions
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21
shared-bindings/time/__init__.c
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@ -39,12 +39,26 @@
//| """time and timing related functions
//|
//| The `time` module is a strict subset of the CPython `cpython:time` module. So, code
//| written in MicroPython will work in CPython but not necessarily the other
//| using `time` written in CircuitPython will work in CPython but not necessarily the other
//| way around."""
//|
//| def monotonic() -> float:
//| """Returns an always increasing value of time with an unknown reference
//| point. Only use it to compare against other values from `monotonic`.
//| point. Only use it to compare against other values from `time.monotonic()`.
//|
//| On most boards, `time.monotonic()` converts a 64-bit millisecond tick counter
//| to a float. Floats on most boards are encoded in 30 bits internally, with
//| effectively 22 bits of precision. The float returned by `time.monotonic()` will
//| accurately represent time to millisecond precision only up to 2**22 milliseconds
//| (about 1.165 hours).
//| At that point it will start losing precision, and its value will change only
//| every second millisecond. At 2**23 milliseconds it will change every fourth
//| millisecond, and so forth.
//|
//| If you need more consistent precision, use `time.monotonic_ns()`, or `supervisor.ticks_ms()`.
//| `time.monotonic_ns()` is not available on boards without long integer support.
//| `supervisor.ticks_ms()` uses intervals of a millisecond, but wraps around, and is not
//| CPython-compatible.
//|
//| :return: the current monotonic time
//| :rtype: float"""
@ -216,7 +230,8 @@ STATIC mp_obj_t time_time(void) {
MP_DEFINE_CONST_FUN_OBJ_0(time_time_obj, time_time);
//| def monotonic_ns() -> int:
//| """Return the time of the monotonic clock, cannot go backward, in nanoseconds.
//| """Return the time of the monotonic clock, which cannot go backward, in nanoseconds.
//| Not available on boards without long integer support.
//|
//| :return: the current time
//| :rtype: int"""