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supervisor: Add a function to get "wrapping" milliseconds

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As discussed in #3410, this is a micropython-compatible (though
differently named) function that allows creation of useful time
and deadline functions in pure python.
This commit is contained in:
Jeff Epler 2021-06-27 16:09:54 -05:00
parent 5a4a80336f
commit 78b20441c1
1 changed files with 51 additions and 0 deletions
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51
shared-bindings/supervisor/__init__.c
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@ -39,6 +39,7 @@
#include "shared-bindings/microcontroller/__init__.h"
#include "shared-bindings/supervisor/__init__.h"
#include "shared-bindings/time/__init__.h"
#include "shared-bindings/supervisor/Runtime.h"
//| """Supervisor settings"""
@ -207,6 +208,55 @@ STATIC mp_obj_t supervisor_set_next_code_file(size_t n_args, const mp_obj_t *pos
}
MP_DEFINE_CONST_FUN_OBJ_KW(supervisor_set_next_code_file_obj, 0, supervisor_set_next_code_file);
//| def ticks_ms() -> int:
//| """Return the time in milliseconds since an unspecified reference point, wrapping after 2**29ms.
//|
//| The value is initialized so that the first overflow occurs about 65
//| seconds after power-on, making it feasible to check that your program
//| works properly around an overflow.
//|
//| The wrap value was chosen so that it is always possible to add
//| or subtract two `ticks_ms` values without overflow on a board without
//| long ints (or without allocating any long integer objects, on boards with
//| long ints).
//|
//| This ticks value comes from a low-accuracy clock internal to the
//| microcontroller, just like `time.monotonic`. Due to its low accuracy
//| and the fact that it "wraps around" every few days, it is intended
//| for working with short term events like advancing an LED animation,
//| not for long term events like counting down the time until a holiday.
//|
//| Addition, subtraction, and comparison of ticks values can be done
//| with routines like the following::
//|
//| _TICKS_PERIOD = const(1<<29)
//| _TICKS_MAX = const(_TICKS_PERIOD-1)
//| _TICKS_HALFPERIOD = const(_TICKS_PERIOD//2)
//|
//| def ticks_add(ticks, delta):
//| "Add a delta to a base number of ticks, performing wraparound at 2**29ms."
//| return (a + b) % _TICKS_PERIOD
//|
//| def ticks_diff(ticks1, ticks2):
//| "Compute the signed difference between two ticks values, assuming that they are within 2**28 ticks"
//| diff = (ticks1 - ticks2) & _TICKS_MAX
//| diff = ((diff + _TICKS_HALFPERIOD) & _TICKS_MAX) - _TICKS_HALFPERIOD
//| return diff
//|
//| def ticks_less(ticks1, ticks2):
//| "Return true iff ticks1 is less than ticks2, assuming that they are within 2**28 ticks"
//| return ticks_diff(ticks1, ticks2) < 0
//|
//| """
//| ...
STATIC mp_obj_t supervisor_ticks_ms(void) {
uint64_t ticks_ms = common_hal_time_monotonic_ms();
return mp_obj_new_int((ticks_ms + 0x1fff0000) % (1 << 29));
}
MP_DEFINE_CONST_FUN_OBJ_0(supervisor_ticks_ms_obj, supervisor_ticks_ms);
STATIC const mp_rom_map_elem_t supervisor_module_globals_table[] = {
{ MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_supervisor) },
{ MP_ROM_QSTR(MP_QSTR_enable_autoreload), MP_ROM_PTR(&supervisor_enable_autoreload_obj) },
@ -217,6 +267,7 @@ STATIC const mp_rom_map_elem_t supervisor_module_globals_table[] = {
{ MP_ROM_QSTR(MP_QSTR_RunReason), MP_ROM_PTR(&supervisor_run_reason_type) },
{ MP_ROM_QSTR(MP_QSTR_set_next_stack_limit), MP_ROM_PTR(&supervisor_set_next_stack_limit_obj) },
{ MP_ROM_QSTR(MP_QSTR_set_next_code_file), MP_ROM_PTR(&supervisor_set_next_code_file_obj) },
{ MP_ROM_QSTR(MP_QSTR_ticks_ms), MP_ROM_PTR(&supervisor_ticks_ms_obj) },
};
STATIC MP_DEFINE_CONST_DICT(supervisor_module_globals, supervisor_module_globals_table);