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Implement local solar time face

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Full implementation of the local solar time complication using the
pveducation.org formula set (LSTM, B, EoT, TC, LST, HRA). EoT and TC
are cached by day-of-year and recomputed once at midnight rollover.

Three display modes cycle with the Alarm button:
  SO HH:MM:SS  — Local Solar Time
  nO HH:MM     — Solar Noon in local clock time
  Hr ±DDD      — Hour Angle in degrees

Location is read from location.u32 on the filesystem. In the simulator
the browser lat/lon globals are written to location.u32 on activation
if not already set, fixing the "no Loc" issue in the emulator.
This commit is contained in:
Raffael Mancini
2026-02-21 18:06:19 +01:00
parent 84c119559d
commit ff3c8a72fc
5 changed files with 316 additions and 2 deletions
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watch-faces/complication/local_solar_time_face.c
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/*
* MIT License
*
* Copyright (c) 2025 Raffael Mancini
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* Solar time formulas follow the notation from:
* https://www.pveducation.org/pvcdrom/properties-of-sunlight/solar-time
*/
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "local_solar_time_face.h"
#include "watch.h"
#include "watch_utility.h"
#include "filesystem.h"
#if __EMSCRIPTEN__
#include <emscripten.h>
#endif
#ifndef M_PI
#define M_PI 3.14159265358979323846f
#endif
/* ---------------------------------------------------------------------------
* Solar time math (pveducation.org notation)
* ---------------------------------------------------------------------------
*
* LSTM = 15 * ΔTUTC [degrees]
* B = (360 / 365) * (d - 81) [degrees] d = day-of-year
* EoT = 9.87*sin(2B) - 7.53*cos(B)
* - 1.5*sin(B) [minutes]
* TC = 4 * (Longitude - LSTM) + EoT [minutes]
* LST = LT + TC/60 [hours]
* HRA = 15 * (LST - 12) [degrees]
* ---------------------------------------------------------------------------
*/
static movement_location_t _load_location(void) {
movement_location_t loc = {0};
filesystem_read_file("location.u32", (char *)&loc.reg, sizeof(loc.reg));
return loc;
}
/* Compute and cache EoT and TC. Call when d != state->last_calc_d. */
static void _compute_daily(local_solar_time_state_t *state, uint16_t d) {
/* LSTM — movement_get_current_timezone_offset() returns seconds from UTC */
float delta_T_UTC = (float)movement_get_current_timezone_offset() / 3600.0f;
float LSTM = 15.0f * delta_T_UTC;
movement_location_t loc = _load_location();
float longitude = (float)(int16_t)loc.bit.longitude / 100.0f;
/* B in radians for sinf/cosf */
float B = (360.0f / 365.0f) * ((float)d - 81.0f) * ((float)M_PI / 180.0f);
state->EoT = 9.87f * sinf(2.0f * B) - 7.53f * cosf(B) - 1.5f * sinf(B);
state->TC = 4.0f * (longitude - LSTM) + state->EoT;
state->last_calc_d = d;
}
/* Recompute if the day-of-year has rolled over. Returns current d. */
static uint16_t _maybe_recompute(local_solar_time_state_t *state, watch_date_time_t dt) {
uint16_t d = watch_utility_days_since_new_year(
(uint16_t)(dt.unit.year + WATCH_RTC_REFERENCE_YEAR),
dt.unit.month,
dt.unit.day
);
if (d != state->last_calc_d && _load_location().reg != 0) {
_compute_daily(state, d);
}
return d;
}
/* LST as total seconds since midnight (0..86399).
* LST = LT + TC/60 => in seconds: LT_sec + TC*60 */
static int32_t _lst_seconds(watch_date_time_t dt, float TC) {
int32_t lt = (int32_t)dt.unit.hour * 3600
+ (int32_t)dt.unit.minute * 60
+ (int32_t)dt.unit.second;
int32_t tc = (int32_t)(TC * 60.0f);
return ((lt + tc) % 86400 + 86400) % 86400;
}
static void _update_display(local_solar_time_state_t *state, watch_date_time_t dt) {
char buf[14];
if (_load_location().reg == 0) {
watch_display_text(WATCH_POSITION_FULL, "SO no Loc");
return;
}
switch (state->mode) {
case LOCAL_SOLAR_TIME_MODE_LST: {
int32_t s = _lst_seconds(dt, state->TC);
sprintf(buf, "SO %02d%02d%02d",
(int)(s / 3600), (int)((s % 3600) / 60), (int)(s % 60));
watch_set_colon();
break;
}
case LOCAL_SOLAR_TIME_MODE_NOON: {
/* Solar noon: moment when LST = 12:00 → LT_noon = 12h - TC/60 */
int32_t s = (int32_t)(( 12.0f - state->TC / 60.0f) * 3600.0f);
s = ((s % 86400) + 86400) % 86400;
sprintf(buf, "nO %02d%02d ", (int)(s / 3600), (int)((s % 3600) / 60));
watch_set_colon();
break;
}
case LOCAL_SOLAR_TIME_MODE_HRA: {
/* HRA = 15 * (LST - 12); negative = morning, positive = afternoon */
int32_t s = _lst_seconds(dt, state->TC);
int16_t hra = (int16_t)roundf(15.0f * ((float)s / 3600.0f - 12.0f));
sprintf(buf, "Hr %+4d ", (int)hra);
watch_clear_colon();
break;
}
default:
return;
}
watch_display_text(WATCH_POSITION_FULL, buf);
}
/* ---- Movement callbacks -------------------------------------------------- */
void local_solar_time_face_setup(uint8_t watch_face_index, void **context_ptr) {
(void)watch_face_index;
if (*context_ptr == NULL) {
*context_ptr = malloc(sizeof(local_solar_time_state_t));
memset(*context_ptr, 0, sizeof(local_solar_time_state_t));
/* last_calc_d == 0 guarantees recomputation on first tick */
}
}
void local_solar_time_face_activate(void *context) {
local_solar_time_state_t *state = (local_solar_time_state_t *)context;
#if __EMSCRIPTEN__
/* In the simulator the browser exposes lat/lon as JS globals.
* Write them to location.u32 if not already set. */
int16_t browser_lat = EM_ASM_INT({ return lat; });
int16_t browser_lon = EM_ASM_INT({ return lon; });
if (browser_lat || browser_lon) {
movement_location_t browser_loc = {0};
filesystem_read_file("location.u32", (char *)&browser_loc.reg, sizeof(browser_loc.reg));
if (browser_loc.reg == 0) {
browser_loc.bit.latitude = browser_lat;
browser_loc.bit.longitude = browser_lon;
filesystem_write_file("location.u32", (char *)&browser_loc.reg, sizeof(browser_loc.reg));
}
}
#endif
/* Force recompute on activation: timezone or location may have changed */
state->last_calc_d = 0;
watch_date_time_t dt = movement_get_local_date_time();
_maybe_recompute(state, dt);
}
bool local_solar_time_face_loop(movement_event_t event, void *context) {
local_solar_time_state_t *state = (local_solar_time_state_t *)context;
switch (event.event_type) {
case EVENT_ACTIVATE:
case EVENT_TICK: {
watch_date_time_t dt = movement_get_local_date_time();
_maybe_recompute(state, dt);
_update_display(state, dt);
break;
}
case EVENT_ALARM_BUTTON_UP:
state->mode = (local_solar_time_mode_t)((state->mode + 1) % LOCAL_SOLAR_TIME_NUM_MODES);
{
watch_date_time_t dt = movement_get_local_date_time();
_update_display(state, dt);
}
break;
case EVENT_LOW_ENERGY_UPDATE: {
if (!watch_sleep_animation_is_running()) watch_start_sleep_animation(1000);
watch_date_time_t dt = movement_get_local_date_time();
_maybe_recompute(state, dt);
_update_display(state, dt);
break;
}
case EVENT_TIMEOUT:
state->mode = LOCAL_SOLAR_TIME_MODE_LST;
if (_load_location().reg == 0) movement_move_to_face(0);
break;
default:
return movement_default_loop_handler(event);
}
return true;
}
void local_solar_time_face_resign(void *context) {
local_solar_time_state_t *state = (local_solar_time_state_t *)context;
state->mode = LOCAL_SOLAR_TIME_MODE_LST;
watch_clear_colon();
}