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Merge branch 'main' of github.com:joeycastillo/Sensor-Watch into main

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This commit is contained in:
Joey Castillo 2021-11-22 17:35:50 -05:00
commit 7817e6696e
15 changed files with 1113 additions and 581 deletions
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3
movement/make/Makefile
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@ -33,7 +33,10 @@ SRCS += \
../watch_faces/thermistor/thermistor_readout_face.c \
../watch_faces/thermistor/thermistor_logging_face.c \
../watch_faces/demos/character_set_face.c \
../watch_faces/demos/voltage_face.c \
../watch_faces/complications/beats_face.c \
../watch_faces/complications/day_one_face.c \
../watch_faces/complications/stopwatch_face.c \
# Leave this line at the bottom of the file; it has all the targets for making your project.
include $(TOP)/rules.mk

18
movement/movement.c
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@ -105,7 +105,7 @@ void app_setup() {
watch_faces[i].setup(&movement_state.settings, &watch_face_contexts[i]);
}
watch_faces[0].activate(&movement_state.settings, watch_face_contexts[0]);
watch_faces[movement_state.current_watch_face].activate(&movement_state.settings, watch_face_contexts[movement_state.current_watch_face]);
event.subsecond = 0;
event.event_type = EVENT_ACTIVATE;
}
@ -143,11 +143,6 @@ bool app_loop() {
}
}
// if we have timed out of our timeout countdown, give the app a hint that they can resign.
if (movement_state.timeout_ticks == 0) {
event.event_type = EVENT_TIMEOUT;
}
// handle background tasks, if the alarm handler told us we need to
if (movement_state.needs_background_tasks_handled) _movement_handle_background_tasks();
@ -181,9 +176,18 @@ bool app_loop() {
event.subsecond = movement_state.subsecond;
can_sleep = watch_faces[movement_state.current_watch_face].loop(event, &movement_state.settings, watch_face_contexts[movement_state.current_watch_face]);
event.event_type = EVENT_NONE;
event.subsecond = 0;
}
// if we have timed out of our timeout countdown, give the app a hint that they can resign.
if (movement_state.timeout_ticks == 0) {
event.event_type = EVENT_TIMEOUT;
event.subsecond = movement_state.subsecond;
watch_faces[movement_state.current_watch_face].loop(event, &movement_state.settings, watch_face_contexts[movement_state.current_watch_face]);
event.event_type = EVENT_NONE;
}
event.subsecond = 0;
return can_sleep && !movement_state.led_on;
}

72
movement/movement.h
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@ -3,27 +3,77 @@
#include <stdio.h>
#include <stdbool.h>
// TODO: none of this is implemented
// Movement Preferences
// These four 32-bit structs store information about the wearer and their preferences. Tentatively, the plan is
// for Movement to use four 32-bit registers for these preferences and to store them in the RTC's backup registers
// 0-3, leaving registers 4-7 available for third party watch faces to use as they see fit.
// * The movement_settings_t struct is provided to all watch faces in the callback functions, and will eventually
// be stored in the RTC's first backup register (BKUP[0]).
// * The movement_location_t and movement_birthdate_t types are defined here, and are tentatively meant to be
// stored in BKUP[1] and BKUP[2], respectively.
// * The movement_reserved_t type is here as a placeholder, because I sense there's some other generally useful
// stuff we'll want to make available to all watch faces and stash in the BKUP[3] register.
// Anyway: Eventually, if Movement supports the BACKUP sleep mode, this will allow these preferences to be stored
// before entering BACKUP mode and and restored after waking from reset.
// movement_settings_t contains global settings that cover watch behavior, including preferences around clock and unit
// display, time zones, buzzer behavior, LED color and low energy mode timeouts.
// Eventually it will be stored in BKUP[0] when Movement enters BACKUP mode.
typedef union {
struct {
uint32_t reserved : 14;
uint32_t button_should_sound : 1; // if true, pressing a button emits a sound.
uint32_t to_interval : 2; // an inactivity interval for asking the active face to resign.
uint32_t le_interval : 3; // 0 to disable low energy mode, or an inactivity interval for going into low energy mode.
uint32_t led_duration : 2; // how many seconds to shine the LED for (x2), or 0 to disable it.
uint32_t led_red_color : 4; // for general purpose illumination, the red LED value (0-15)
uint32_t led_green_color : 4; // for general purpose illumination, the green LED value (0-15)
bool button_should_sound : 1; // if true, pressing a button emits a sound.
uint8_t to_interval : 2; // an inactivity interval for asking the active face to resign.
uint8_t le_interval : 3; // 0 to disable low energy mode, or an inactivity interval for going into low energy mode.
uint8_t led_duration : 2; // how many seconds to shine the LED for (x2), or 0 to disable it.
uint8_t led_red_color : 4; // for general purpose illumination, the red LED value (0-15)
uint8_t led_green_color : 4; // for general purpose illumination, the green LED value (0-15)
uint8_t time_zone : 6; // TODO: an integer representing an index in the (to be implemented) time zone table.
// while Movement itself doesn't implement a clock or display units, it may make sense to include some
// global settings for watch faces to check. The 12/24 hour preference could inform a clock or a
// time-oriented complication like a sunrise/sunset timer, and a simple locale preference could tell an
// altimeter to display feet or meters as easily as it tells a thermometer to display degrees in F or C.
uint32_t clock_mode_24h : 1; // indicates whether clock should use 12 or 24 hour mode.
uint32_t use_imperial_units : 1; // indicates whether to use metric units (the default) or imperial.
bool clock_mode_24h : 1; // indicates whether clock should use 12 or 24 hour mode.
bool use_imperial_units : 1; // indicates whether to use metric units (the default) or imperial.
uint8_t reserved : 8; // room for more preferences if needed.
} bit;
uint32_t value;
uint32_t reg;
} movement_settings_t;
// movement_location_t is for storing the wearer's location. This will be useful for astronomical calculations such as
// sunrise and sunset, or predictions of visible satellite passes.
// If you create a UI for this register or need to access it, look for it in the RTC's BKUP[1] register.
typedef union {
struct {
int16_t latitude : 16; // signed latutide in hundredths of a degree
int16_t longitude : 16; // signed longitude in hundredths of a degree
} bit;
uint32_t reg;
} movement_location_t;
// movement_birthdate_t is for storing the user's birth date. This will be useful for calculating the user's age — or
// hey, playing happy birthday at midnight? Fields for birth time (with hour and minute resolution) are also available,
// partly because they fit so nicely, but also because they can be useful for certain astrological calculations.
// If you create a UI for birth date or need to access it, look for it in the RTC's BKUP[2] register.
typedef union {
struct {
uint16_t year : 12; // good through the year 4095
uint8_t month : 4;
uint8_t day : 5;
uint8_t hour : 5;
uint8_t minute : 6;
} bit;
uint32_t reg;
} movement_birthdate_t;
// movement_reserved_t is a placeholder for future use of the BKUP[3] register.
typedef union {
struct {
uint32_t reserved : 32;
} bit;
uint32_t reg;
} movement_reserved_t;
typedef enum {
EVENT_NONE = 0, // There is no event to report.
EVENT_ACTIVATE, // Your watch face is entering the foreground.

3
movement/movement_config.h
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@ -9,6 +9,9 @@
#include "thermistor_logging_face.h"
#include "character_set_face.h"
#include "beats_face.h"
#include "day_one_face.h"
#include "voltage_face.h"
#include "stopwatch_face.h"
const watch_face_t watch_faces[] = {
simple_clock_face,

1
movement/watch_faces/clock/simple_clock_face.c
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@ -28,7 +28,6 @@ bool simple_clock_face_loop(movement_event_t event, movement_settings_t *setting
switch (event.event_type) {
case EVENT_ACTIVATE:
case EVENT_TICK:
case EVENT_TIMEOUT:
case EVENT_LOW_ENERGY_UPDATE:
date_time = watch_rtc_get_date_time();
previous_date_time = *((uint32_t *)context);

2
movement/watch_faces/complications/beats_face.c
View File

@ -26,6 +26,7 @@ bool beats_face_loop(movement_event_t event, movement_settings_t *settings, void
watch_date_time date_time;
switch (event.event_type) {
case EVENT_ACTIVATE:
case EVENT_TICK:
date_time = watch_rtc_get_date_time();
beats = clock2beats(date_time.unit.hour, date_time.unit.minute, date_time.unit.second, event.subsecond, UTC_OFFSET);
@ -34,6 +35,7 @@ bool beats_face_loop(movement_event_t event, movement_settings_t *settings, void
watch_display_string(buf, 0);
break;
case EVENT_LOW_ENERGY_UPDATE:
if (!watch_tick_animation_is_running()) watch_start_tick_animation(432);
date_time = watch_rtc_get_date_time();
beats = clock2beats(date_time.unit.hour, date_time.unit.minute, date_time.unit.second, event.subsecond, UTC_OFFSET);
sprintf(buf, "bt %4d ", (int)beats);

177
movement/watch_faces/complications/day_one_face.c Normal file
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@ -0,0 +1,177 @@
#include <stdlib.h>
#include <string.h>
#include "day_one_face.h"
#include "watch.h"
uint32_t _day_one_face_juliandaynum(uint16_t year, uint16_t month, uint16_t day) {
// from here: https://en.wikipedia.org/wiki/Julian_day#Julian_day_number_calculation
return (1461 * (year + 4800 + (month - 14) / 12)) / 4 + (367 * (month - 2 - 12 * ((month - 14) / 12))) / 12 - (3 * ((year + 4900 + (month - 14) / 12) / 100))/4 + day - 32075;
}
void _day_one_face_update(day_one_state_t state) {
char buf[14];
watch_date_time date_time = watch_rtc_get_date_time();
uint32_t julian_date = _day_one_face_juliandaynum(date_time.unit.year + WATCH_RTC_REFERENCE_YEAR, date_time.unit.month, date_time.unit.day);
uint32_t julian_birthdate = _day_one_face_juliandaynum(state.birth_year, state.birth_month, state.birth_day);
sprintf(buf, "DA %6ld", julian_date - julian_birthdate);
watch_display_string(buf, 0);
}
void day_one_face_setup(movement_settings_t *settings, void ** context_ptr) {
(void) settings;
if (*context_ptr == NULL) {
*context_ptr = malloc(sizeof(day_one_state_t));
memset(*context_ptr, 0, sizeof(day_one_state_t));
movement_birthdate_t movement_birthdate = (movement_birthdate_t) watch_get_backup_data(2);
if (movement_birthdate.reg == 0) {
// if birth date is totally blank, set a reasonable starting date. this works well for anyone under 63, but
// you can keep pressing to go back to 1900; just pass the current year. also picked this date because if you
// set it to 1959-01-02, it counts up from the launch of Luna-1, the first spacecraft to leave the well.
movement_birthdate.bit.year = 1959;
movement_birthdate.bit.month = 1;
movement_birthdate.bit.day = 1;
watch_store_backup_data(movement_birthdate.reg, 2);
}
}
}
void day_one_face_activate(movement_settings_t *settings, void *context) {
(void) settings;
day_one_state_t *state = (day_one_state_t *)context;
// stash the current year, useful in birthday setting mode.
watch_date_time date_time = watch_rtc_get_date_time();
state->current_year = date_time.unit.year + WATCH_RTC_REFERENCE_YEAR;
// reset the current page to 0, display days alive.
state->current_page = 0;
// fetch the user's birth date from the birthday register.
movement_birthdate_t movement_birthdate = (movement_birthdate_t) watch_get_backup_data(2);
state->birth_year = movement_birthdate.bit.year;
state->birth_month = movement_birthdate.bit.month;
state->birth_day = movement_birthdate.bit.day;
}
bool day_one_face_loop(movement_event_t event, movement_settings_t *settings, void *context) {
(void) settings;
day_one_state_t *state = (day_one_state_t *)context;
const uint8_t days_in_month[12] = {31, 29, 31, 30, 31, 30, 30, 31, 30, 31, 30, 31};
char buf[6];
switch (event.event_type) {
case EVENT_ACTIVATE:
_day_one_face_update(*state);
break;
case EVENT_LOW_ENERGY_UPDATE:
case EVENT_TICK:
if (state->current_page != 0) {
// if in settings mode, update whatever the current page is
switch (state->current_page) {
case 1:
watch_display_string("YR ", 0);
if (event.subsecond % 2) {
sprintf(buf, "%4d", state->birth_year);
watch_display_string(buf, 4);
}
break;
case 2:
watch_display_string("MO ", 0);
if (event.subsecond % 2) {
sprintf(buf, "%2d", state->birth_month);
watch_display_string(buf, 4);
}
break;
case 3:
watch_display_string("DA ", 0);
if (event.subsecond % 2) {
sprintf(buf, "%2d", state->birth_day);
watch_display_string(buf, 6);
}
break;
}
} else {
// otherwise, check if we have to update. the display only needs to change at midnight!
watch_date_time date_time = watch_rtc_get_date_time();
if (date_time.unit.hour == 0 && date_time.unit.minute == 0 && date_time.unit.second == 0) {
_day_one_face_update(*state);
}
}
break;
case EVENT_MODE_BUTTON_UP:
movement_move_to_next_face();
break;
case EVENT_LIGHT_BUTTON_DOWN:
// only illuminate if we're in display mode
if (state->current_page == 0) movement_illuminate_led();
break;
case EVENT_LIGHT_BUTTON_UP:
// otherwise use the light button to advance settings pages.
if (state->current_page != 0) {
// go to next setting page...
state->current_page = (state->current_page + 1) % 4;
if (state->current_page == 0) {
// ...unless we've been pushed back to display mode.
movement_request_tick_frequency(1);
// force display since it normally won't update til midnight.
_day_one_face_update(*state);
}
}
break;
case EVENT_ALARM_BUTTON_UP:
// if we are on a settings page, increment whatever value we're setting.
if (state->current_page != 0) {
state->birthday_changed = true;
switch (state->current_page) {
case 1:
state->birth_year = state->birth_year + 1;
if (state->birth_year > state->current_year) state->birth_year = 1900;
break;
case 2:
state->birth_month = (state->birth_month % 12) + 1;
break;
case 3:
state->birth_day = state->birth_day + 1;
if (state->birth_day == 0 || state->birth_day > days_in_month[state->birth_month - 1]) {
state->birth_day = 1;
}
break;
}
}
break;
case EVENT_ALARM_LONG_PRESS:
// if we aren't already in settings mode, put us there.
if (state->current_page == 0) {
state->current_page++;
movement_request_tick_frequency(4);
}
break;
case EVENT_TIMEOUT:
// return home if we're on a settings page (this saves our changes when we resign).
if (state->current_page != 0) {
movement_move_to_face(0);
}
default:
break;
}
return true;
}
void day_one_face_resign(movement_settings_t *settings, void *context) {
(void) settings;
day_one_state_t *state = (day_one_state_t *)context;
movement_request_tick_frequency(1);
// if the user changed their birth date, store it to the birth date register
if (state->birthday_changed) {
day_one_state_t *state = (day_one_state_t *)context;
movement_birthdate_t movement_birthdate = (movement_birthdate_t) watch_get_backup_data(2);
movement_birthdate.bit.year = state->birth_year;
movement_birthdate.bit.month = state->birth_month;
movement_birthdate.bit.day = state->birth_day;
watch_store_backup_data(movement_birthdate.reg, 2);
state->birthday_changed = false;
}
}

31
movement/watch_faces/complications/day_one_face.h Normal file
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@ -0,0 +1,31 @@
#ifndef DAY_ONE_FACE_H_
#define DAY_ONE_FACE_H_
#include "movement.h"
// The Day One face is designed to count upwards from the wearer's date of birth. It also functions as an
// interface for setting the birth date register, which other watch faces can use for various purposes.
typedef struct {
uint8_t current_page;
uint16_t current_year;
uint16_t birth_year;
uint8_t birth_month;
uint8_t birth_day;
bool birthday_changed;
} day_one_state_t;
void day_one_face_setup(movement_settings_t *settings, void ** context_ptr);
void day_one_face_activate(movement_settings_t *settings, void *context);
bool day_one_face_loop(movement_event_t event, movement_settings_t *settings, void *context);
void day_one_face_resign(movement_settings_t *settings, void *context);
static const watch_face_t day_one_face = {
day_one_face_setup,
day_one_face_activate,
day_one_face_loop,
day_one_face_resign,
NULL
};
#endif // DAY_ONE_FACE_H_

76
movement/watch_faces/complications/stopwatch_face.c Normal file
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@ -0,0 +1,76 @@
#include <stdlib.h>
#include <string.h>
#include "stopwatch_face.h"
#include "watch.h"
void stopwatch_face_setup(movement_settings_t *settings, void ** context_ptr) {
(void) settings;
if (*context_ptr == NULL) *context_ptr = malloc(sizeof(stopwatch_state_t));
}
void stopwatch_face_activate(movement_settings_t *settings, void *context) {
(void) settings;
memset(context, 0, sizeof(stopwatch_state_t));
}
bool stopwatch_face_loop(movement_event_t event, movement_settings_t *settings, void *context) {
(void) settings;
stopwatch_state_t *stopwatch_state = (stopwatch_state_t *)context;
char buf[14];
switch (event.event_type) {
case EVENT_ACTIVATE:
watch_set_colon();
stopwatch_state->running = false;
watch_display_string("st 00000", 0);
break;
case EVENT_TICK:
if (stopwatch_state->running) {
stopwatch_state->seconds++;
if (stopwatch_state->seconds == 60) {
stopwatch_state->minutes++;
stopwatch_state->seconds = 0;
}
if (stopwatch_state->minutes == 60) {
stopwatch_state->hours++;
stopwatch_state->minutes = 0;
}
}
sprintf(buf, "st%2d%02d%02d", stopwatch_state->hours, stopwatch_state->minutes, stopwatch_state->seconds);
watch_display_string(buf, 0);
break;
case EVENT_MODE_BUTTON_UP:
movement_move_to_next_face();
break;
case EVENT_LIGHT_BUTTON_DOWN:
movement_illuminate_led();
if (!stopwatch_state->running) {
stopwatch_state->seconds = 0;
stopwatch_state->minutes = 0;
stopwatch_state->hours = 0;
watch_display_string("st 00000", 0);
}
break;
case EVENT_ALARM_BUTTON_DOWN:
stopwatch_state->running = !stopwatch_state->running;
break;
case EVENT_TIMEOUT:
// explicitly ignore the timeout event so we stay on screen
break;
case EVENT_LOW_ENERGY_UPDATE:
stopwatch_state->running = false;
watch_set_indicator(WATCH_INDICATOR_BELL);
break;
default:
break;
}
return true;
}
void stopwatch_face_resign(movement_settings_t *settings, void *context) {
(void) settings;
(void) context;
}

26
movement/watch_faces/complications/stopwatch_face.h Normal file
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@ -0,0 +1,26 @@
#ifndef STOPWATCH_FACE_H_
#define STOPWATCH_FACE_H_
#include "movement.h"
typedef struct {
bool running;
uint8_t seconds;
uint8_t minutes;
uint8_t hours;
} stopwatch_state_t;
void stopwatch_face_setup(movement_settings_t *settings, void ** context_ptr);
void stopwatch_face_activate(movement_settings_t *settings, void *context);
bool stopwatch_face_loop(movement_event_t event, movement_settings_t *settings, void *context);
void stopwatch_face_resign(movement_settings_t *settings, void *context);
static const watch_face_t stopwatch_face = {
stopwatch_face_setup,
stopwatch_face_activate,
stopwatch_face_loop,
stopwatch_face_resign,
NULL
};
#endif // STOPWATCH_FACE_H_

66
movement/watch_faces/demos/voltage_face.c Normal file
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@ -0,0 +1,66 @@
#include <stdlib.h>
#include <string.h>
#include "voltage_face.h"
#include "watch.h"
void _voltage_face_update_display() {
char buf[14];
float voltage = (float)watch_get_vcc_voltage() / 1000.0;
sprintf(buf, "BA %4.2f V", voltage);
// printf("%s\n", buf);
watch_display_string(buf, 0);
}
void voltage_face_setup(movement_settings_t *settings, void ** context_ptr) {
(void) settings;
(void) context_ptr;
}
void voltage_face_activate(movement_settings_t *settings, void *context) {
(void) settings;
(void) context;
watch_enable_adc();
// if we set the reference voltage here, watch_get_vcc_voltage won't do it over and over
watch_set_analog_reference_voltage(ADC_REFERENCE_INTREF);
}
bool voltage_face_loop(movement_event_t event, movement_settings_t *settings, void *context) {
(void) settings;
(void) context;
watch_date_time date_time;
switch (event.event_type) {
case EVENT_MODE_BUTTON_UP:
movement_move_to_next_face();
break;
case EVENT_LIGHT_BUTTON_DOWN:
movement_illuminate_led();
break;
case EVENT_ACTIVATE:
_voltage_face_update_display();
break;
case EVENT_TICK:
date_time = watch_rtc_get_date_time();
if (date_time.unit.second % 5 == 4) {
watch_set_indicator(WATCH_INDICATOR_SIGNAL);
} else if (date_time.unit.second % 5 == 0) {
_voltage_face_update_display();
watch_clear_indicator(WATCH_INDICATOR_SIGNAL);
}
break;
case EVENT_TIMEOUT:
movement_move_to_face(0);
break;
default:
break;
}
return true;
}
void voltage_face_resign(movement_settings_t *settings, void *context) {
(void) settings;
(void) context;
// make sure to restore the default in the end.
watch_set_analog_reference_voltage(ADC_REFCTRL_REFSEL_INTVCC2_Val);
watch_disable_adc();
}

19
movement/watch_faces/demos/voltage_face.h Normal file
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@ -0,0 +1,19 @@
#ifndef VOLTAGE_FACE_H_
#define VOLTAGE_FACE_H_
#include "movement.h"
void voltage_face_setup(movement_settings_t *settings, void ** context_ptr);
void voltage_face_activate(movement_settings_t *settings, void *context);
bool voltage_face_loop(movement_event_t event, movement_settings_t *settings, void *context);
void voltage_face_resign(movement_settings_t *settings, void *context);
static const watch_face_t voltage_face = {
voltage_face_setup,
voltage_face_activate,
voltage_face_loop,
voltage_face_resign,
NULL
};
#endif // VOLTAGE_FACE_H_

1124
utils/flash_watch_pyruler/bootloader.h
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File diff suppressed because it is too large Load Diff

29
watch-library/watch/watch_adc.c
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@ -138,6 +138,35 @@ void watch_set_analog_sampling_length(uint8_t cycles) {
_watch_sync_adc();
}
void watch_set_analog_reference_voltage(watch_adc_reference_voltage reference) {
ADC->CTRLA.bit.ENABLE = 0;
if (reference == ADC_REFERENCE_INTREF) SUPC->VREF.bit.VREFOE = 1;
else SUPC->VREF.bit.VREFOE = 0;
ADC->REFCTRL.bit.REFSEL = reference;
ADC->CTRLA.bit.ENABLE = 1;
_watch_sync_adc();
// throw away one measurement after reference change (the channel doesn't matter).
_watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_SCALEDCOREVCC);
}
uint16_t watch_get_vcc_voltage() {
// stash the previous reference so we can restore it when we're done.
uint8_t oldref = ADC->REFCTRL.bit.REFSEL;
// if we weren't already using the internal reference voltage, select it now.
if (oldref != ADC_REFERENCE_INTREF) watch_set_analog_reference_voltage(ADC_REFERENCE_INTREF);
// get the data
uint32_t raw_val = _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_SCALEDIOVCC_Val);
// restore the old reference, if needed.
if (oldref != ADC_REFERENCE_INTREF) watch_set_analog_reference_voltage(oldref);
return (uint16_t)((raw_val * 1000) / (1024 * 1 << ADC->AVGCTRL.bit.SAMPLENUM));
}
inline void watch_disable_analog_input(const uint8_t pin) {
gpio_set_pin_function(pin, GPIO_PIN_FUNCTION_OFF);
}

47
watch-library/watch/watch_adc.h
View File

@ -94,6 +94,53 @@ void watch_set_analog_num_samples(uint16_t samples);
**/
void watch_set_analog_sampling_length(uint8_t cycles);
typedef enum {
ADC_REFERENCE_INTREF = ADC_REFCTRL_REFSEL_INTREF_Val,
ADC_REFERENCE_VCC_DIV1POINT6 = ADC_REFCTRL_REFSEL_INTVCC0_Val,
ADC_REFERENCE_VCC_DIV2 = ADC_REFCTRL_REFSEL_INTVCC1_Val,
ADC_REFERENCE_VCC = ADC_REFCTRL_REFSEL_INTVCC2_Val,
} watch_adc_reference_voltage;
/** @brief Selects the reference voltage to use for analog readings. Default is ADC_REFERENCE_VCC.
* @param reference One of ADC_REFERENCE_VCC, ADC_REFERENCE_VCC_DIV1POINT6, ADC_REFERENCE_VCC_DIV2
* or ADC_REFERENCE_INTREF.
* @details In order to turn an analog voltage into a 16-bit integer, the ADC needs to compare the
* measured voltage to a reference point. For example, if you were powering the watch with
* VCC == 3.0V and you had two 10K resistors connected in series from 3V to GND, you could
* expect to get 3 volts when you measure the top of the voltage divider, 0 volts at the
* bottom, and 1.5 volts in the middle. If you read these values uising a reference voltage
* of ADC_REFERENCE_VCC, the top value would be about 65535, the bottom about 0, and the
* middle about 32768. However! If we used ADC_REFERENCE_VCC_DIV2 as our reference, we would
* expect to get 65535 both at the top and the middle, because the largest value the ADC can
* measure in this configutation is 1.5V (VCC / 2).
*
* By changing the reference voltage from ADC_REFERENCE_VCC to ADC_REFERENCE_VCC_DIV1POINT6
* or ADC_REFERENCE_VCC_DIV2, you can get more resolution when measuring small voltages (i.e.
* a phototransistor circuit in low light).
*
* There is also a special reference voltage called ADC_REFERENCE_INTREF. The SAM L22's
* Supply Controller provides a selectable voltage reference (by default, 1.024 V) that you
* can select as a reference voltage for ADC conversions. Unlike the three references we
* talked about in the last paragraph, this reference voltage does not depend on VCC, which
* makes it very useful for measuring the battery voltage (since you can't really compare
* VCC to itself). You can change the INTREF voltage to 2.048 or 4.096 V by poking at the
* supply controller's VREF register, but the watch library does not support this use case.
**/
void watch_set_analog_reference_voltage(watch_adc_reference_voltage reference);
/** @brief Returns the voltage of the VCC supply in millivolts (i.e. 3000 mV == 3.0 V). If running on
* a coin cell, this will be the battery voltage.
* @details Unlike other ADC functions, this function does not return a raw value from the ADC, but
* rather scales it to an actual number of millivolts. This is because the ADC doesn't let
* us measure VCC per se; it instead lets us measure VCC / 4, and we choose to measure it
* against the internal reference voltage of 1.024 V. In short, the ADC gives us a number
* that's complicated to deal with, so we just turn it into a useful number for you :)
* @note This function depends on INTREF being 1.024V. If you have changed it by poking at the supply
* controller's VREF.SEL bits, this function will return inaccurate values.
*/
uint16_t watch_get_vcc_voltage();
/** @brief Disables the analog circuitry on the selected pin.
* @param pin One of pins A0-A4.
*/