Utility Functions

This section covers various useful functions that don't fit anywhere else. More...

Functions
const char *	watch_utility_get_weekday (watch_date_time date_time)
	Returns a two-letter weekday for the given timestamp, suitable for display in positions 0-1 of the watch face. More...
uint32_t	watch_utility_convert_to_unix_time (uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second, uint32_t utc_offset)
	Returns the UNIX time (seconds since 1970) for a given date/time in UTC. More...
uint32_t	watch_utility_date_time_to_unix_time (watch_date_time date_time, uint32_t utc_offset)
	Returns the UNIX time (seconds since 1970) for a given watch_date_time struct. More...
watch_date_time	watch_utility_date_time_from_unix_time (uint32_t timestamp, uint32_t utc_offset)
	Returns the UNIX time (seconds since 1970) for a given watch_date_time struct. More...
watch_date_time	watch_utility_date_time_convert_zone (watch_date_time date_time, uint32_t origin_utc_offset, uint32_t destination_utc_offset)
	Converts a time from a given time zone to another time zone. More...
float	watch_utility_thermistor_temperature (uint16_t value, bool highside, float b_coefficient, float nominal_temperature, float nominal_resistance, float series_resistance)
	Returns a temperature in degrees Celsius for a given thermistor voltage divider circuit. More...

Detailed Description

This section covers various useful functions that don't fit anywhere else.

Function Documentation

watch_utility_convert_to_unix_time()

uint32_t watch_utility_convert_to_unix_time	(	uint16_t	year,
		uint8_t	month,
		uint8_t	day,
		uint8_t	hour,
		uint8_t	minute,
		uint8_t	second,
		uint32_t	utc_offset
	)

Returns the UNIX time (seconds since 1970) for a given date/time in UTC.

Parameters

date_time	The watch_date_time that you wish to convert.
year	The year of the date you wish to convert.
month	The month of the date you wish to convert.
day	The day of the date you wish to convert.
hour	The hour of the date you wish to convert.
minute	The minute of the date you wish to convert.
second	The second of the date you wish to convert.
utc_offset	The number of seconds that date_time is offset from UTC, or 0 if the time is UTC.

Returns

A UNIX timestamp for the given date/time and UTC offset.

Note

Implemented by Wesley Ellis (tahnok) and based on BSD-licensed code by Josh Haberman: https://blog.reverberate.org/2020/05/12/optimizing-date-algorithms.html

watch_utility_date_time_convert_zone()

watch_date_time watch_utility_date_time_convert_zone	(	watch_date_time	date_time,
		uint32_t	origin_utc_offset,
		uint32_t	destination_utc_offset
	)

Converts a time from a given time zone to another time zone.

Parameters

date_time	The watch_date_time that you wish to convert
origin_utc_offset	The number of seconds from UTC in the origin time zone
destination_utc_offset	The number of seconds from UTC in the destination time zone

Returns

A watch_date_time for the given UNIX timestamp and UTC offset, or if outside the range that watch_date_time can represent, a watch_date_time with all fields set to 0.

Note

Adapted from MIT-licensed code from musl, Copyright © 2005-2014 Rich Felker, et al.: https://github.com/esmil/musl/blob/1cc81f5cb0df2b66a795ff0c26d7bbc4d16e13c6/src/time/__secs_to_tm.c

watch_utility_date_time_from_unix_time()

watch_date_time watch_utility_date_time_from_unix_time	(	uint32_t	timestamp,
		uint32_t	utc_offset
	)

Returns the UNIX time (seconds since 1970) for a given watch_date_time struct.

Parameters

timestamp	The UNIX timestamp that you wish to convert.
utc_offset	The number of seconds that you wish date_time to be offset from UTC.

Returns

A watch_date_time for the given UNIX timestamp and UTC offset, or if outside the range that watch_date_time can represent, a watch_date_time with all fields set to 0.

Note

Adapted from MIT-licensed code from musl, Copyright © 2005-2014 Rich Felker, et al.: https://github.com/esmil/musl/blob/1cc81f5cb0df2b66a795ff0c26d7bbc4d16e13c6/src/time/__secs_to_tm.c

watch_utility_date_time_to_unix_time()

uint32_t watch_utility_date_time_to_unix_time	(	watch_date_time	date_time,
		uint32_t	utc_offset
	)

Returns the UNIX time (seconds since 1970) for a given watch_date_time struct.

Parameters

date_time	The watch_date_time that you wish to convert.
utc_offset	The number of seconds that date_time is offset from UTC, or 0 if the time is UTC.

Returns

A UNIX timestamp for the given watch_date_time and UTC offset.

watch_utility_get_weekday()

const char* watch_utility_get_weekday

(

watch_date_time

date_time

)

Returns a two-letter weekday for the given timestamp, suitable for display in positions 0-1 of the watch face.

Parameters

date_time

The watch_date_time whose weekday you want.

watch_utility_thermistor_temperature()

float watch_utility_thermistor_temperature	(	uint16_t	value,
		bool	highside,
		float	b_coefficient,
		float	nominal_temperature,
		float	nominal_resistance,
		float	series_resistance
	)

Returns a temperature in degrees Celsius for a given thermistor voltage divider circuit.

Parameters

value	The raw analog reading from the thermistor pin (0-65535)
highside	True if the thermistor is connected to VCC and the series resistor is connected to GND; false if the thermistor is connected to GND and the series resistor is connected to VCC.
b_coefficient	From your thermistor's data sheet, the B25/85 coefficient. A typical value will be between 2000 and 5000.
nominal_temperature	From your thermistor's data sheet, the temperature (in Celsius) at which the thermistor's resistance is at its nominal value.
nominal_resistance	The thermistor's resistance at the nominal temperature.
series_resistance	The value of the other resistor in the voltage divider.

Note

Ported from Adafruit's MIT-licensed CircuitPython thermistor code, (c) 2017 Scott Shawcroft: https://github.com/adafruit/Adafruit_CircuitPython_Thermistor/blob/main/adafruit_thermistor.py