Hi,
I'm currently reading the local time from a client via the CTS over BLE, but need to convert that in my nRF52832 to UTC time. Is there some API's available that do this? I can't seem to find any, and was thinking "surely, someone has done this before?"
Cheers,
Mike
Hello Mike,
Should we continue the discussion in Getting Time Zone and Daylight Savings info out of CTS ?
Best regards,
Simon
Hello Mike,
Should we continue the discussion in Getting Time Zone and Daylight Savings info out of CTS ?
Best regards,
Simon
OK, ended up sorting this out for myself. Below is my code. I'm sure someone could make this more efficient, but I'm a hardware guy so just happy it works! Haha.
At the moment I'm just hard coding the values for .timeZone and .dst into my bt_cts_local_time structure, as I've not yet been able to extract this from the CTS. Plus it made it easier for me to test all the various scenarios.
#define DAYS_IN_WEEK 7
#define MONTHS_IN_YEAR 12
#define MINS_IN_HOUR 60
#define HOURS_IN_DAY 24
#define JANUARY 1
#define FEBRUARY 2
#define MARCH 3
#define DECEMBER 12
/**
* @brief CTS Local Time structure
*
* @param timeZone Offset from UTC in hours
* @param dst Daylight Savings Time: 1 = active, 0 = inactive
*/
struct bt_cts_local_time
{
int8_t timeZone; /**< Current Time Zone */
uint8_t dst; /**< Daylight Saving Time value */
} ;
struct bt_cts_current_time local_time, utc_time;
struct bt_cts_local_time local_time_info;
uint8_t daysInMonth[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
// Convert time from Current Time Service to UTC time
// cts_current_time = time from CTS
// cts_local_time = local time info (time zone and DST) from CTS
// utc_time = time converted to UTC
void convert_to_utc_time (struct bt_cts_current_time *cts_current_time, struct bt_cts_local_time *cts_local_time, struct bt_cts_current_time *utc_time)
{
int8_t minOffset = 0,
hourOffset = 0,
dayOffset = 0,
monthOffset = 0,
yearOffset = 0,
days_in_current_month = 0,
days_in_previous_month = 0;
uint8_t week_day,
day,
month,
hour,
min;
uint16_t year;
bool isLeapYear;
week_day = cts_current_time->exact_time_256.day_of_week;
day = cts_current_time->exact_time_256.day;
month = cts_current_time->exact_time_256.month;
hour = cts_current_time->exact_time_256.hours;
min = cts_current_time->exact_time_256.minutes;
year = cts_current_time->exact_time_256.year;
/* Calculate time offset due to local time zone and daylight savings */
// .timeZone and .dst are expressed in multiples of 15 minutes
// Negative offset means local time is behind UTC, positive offset means local time is ahead of UTC
hourOffset = (int8_t)((cts_local_time->timeZone/4) + (cts_local_time->dst/4));
minOffset = (int8_t)((cts_local_time->timeZone%4) + (cts_local_time->dst%4))*15;
if (year%4 == 0) {
isLeapYear = true;
if (month == FEBRUARY) {
days_in_current_month = daysInMonth[FEBRUARY]+1;
}
else {
days_in_current_month = daysInMonth[month];
}
if (month == MARCH) {
days_in_previous_month = daysInMonth[FEBRUARY]+1;
}
else if (month == JANUARY) {
days_in_previous_month = daysInMonth[DECEMBER];
}
else {
days_in_previous_month = daysInMonth[month-1];
}
}
else {
isLeapYear = false;
if (month == JANUARY) {
days_in_previous_month = daysInMonth[DECEMBER];
}
else {
days_in_previous_month = daysInMonth[month-1];
}
days_in_current_month = daysInMonth[month];
}
/* Update mintues */
if (minOffset < 0) {
//Local behind UTC - increase minutes
if ((min + abs(minOffset)) > MINS_IN_HOUR) {
++hourOffset;
min = (min + abs(minOffset)) - MINS_IN_HOUR;
}
else {
min = (min + abs(minOffset));
}
}
else if (minOffset >= 0) {
//Local ahead of UTC - reduce minutes
if (min < minOffset) {
--hourOffset;
min = MINS_IN_HOUR + min - minOffset;
}
else {
min = min - minOffset;
}
}
/* Update hours */
if (hourOffset < 0) {
//Local behind UTC - increase hours
if ((hour + abs(hourOffset)) > HOURS_IN_DAY) {
++dayOffset;
hour = (hour + abs(hourOffset)) - HOURS_IN_DAY;
}
else {
hour = (hour + abs(hourOffset));
}
}
else if (hourOffset >= 0) {
//Local ahead of UTC - reduce hours
if (hour < hourOffset) {
--dayOffset;
hour = HOURS_IN_DAY + hour - hourOffset;
}
else {
hour = hour - hourOffset;
}
}
/* Update day of month */
if (dayOffset >= 0) {
if ((day + dayOffset) > days_in_current_month) {
++monthOffset;
day = (day + dayOffset) - days_in_current_month;
}
else {
day = day + dayOffset;
}
}
else if (dayOffset < 0) {
if (day <= abs(dayOffset)) {
--monthOffset;
day = days_in_previous_month + day + dayOffset;
}
else {
day = day + dayOffset;
}
}
/* Update month */
if (monthOffset >= 0) {
if ((month + monthOffset) > MONTHS_IN_YEAR) {
++yearOffset;
month = (month + monthOffset) - MONTHS_IN_YEAR;
}
else {
month = month + monthOffset;
}
}
else if (monthOffset < 0) {
if (month <= abs(monthOffset)) {
--yearOffset;
month = MONTHS_IN_YEAR + month + monthOffset;
}
else {
month = month + monthOffset;
}
}
/* Update day of week */
if (dayOffset >= 0) {
if ((week_day + dayOffset) > DAYS_IN_WEEK) {
week_day = (week_day + dayOffset) - DAYS_IN_WEEK;
}
else {
week_day = week_day + dayOffset;
}
}
else if (dayOffset < 0) {
if (week_day <= abs(dayOffset)) {
week_day = DAYS_IN_WEEK + week_day + dayOffset;
}
else {
week_day = week_day + dayOffset;
}
}
/* Set UTC time */
utc_time->exact_time_256.seconds = cts_current_time->exact_time_256.seconds;
utc_time->exact_time_256.minutes = min;
utc_time->exact_time_256.hours = hour;
utc_time->exact_time_256.day_of_week = week_day;
utc_time->exact_time_256.day = day;
utc_time->exact_time_256.month = month;
utc_time->exact_time_256.year = year + yearOffset;
}
Cheers,
Mike
There you go. I'm glad you found a solution that works for you.
Best regards,
Simon