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AP_GPS: use mktime for NMEA and MTK time conversion

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this fixes NMEA time handling, which was off by 3 days
This commit is contained in:
Andrew Tridgell 2020-10-19 21:35:29 +11:00
parent 7562eef4c1
commit e529d475d4
1 changed files with 15 additions and 22 deletions
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37
libraries/AP_GPS/GPS_Backend.cpp
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@ -16,6 +16,8 @@
#include "AP_GPS.h"
#include "GPS_Backend.h"
#include <AP_Logger/AP_Logger.h>
#include <time.h>
#include <AP_RTC/AP_RTC.h>
#define GPS_BACKEND_DEBUGGING 0
@ -76,34 +78,25 @@ int16_t AP_GPS_Backend::swap_int16(int16_t v) const
*/
void AP_GPS_Backend::make_gps_time(uint32_t bcd_date, uint32_t bcd_milliseconds)
{
uint8_t year, mon, day, hour, min, sec;
uint16_t msec;
struct tm tm {};
year = bcd_date % 100;
mon = (bcd_date / 100) % 100;
day = bcd_date / 10000;
tm.tm_year = 100U + bcd_date % 100U;
tm.tm_mon = ((bcd_date / 100U) % 100U)-1;
tm.tm_mday = bcd_date / 10000U;
uint32_t v = bcd_milliseconds;
msec = v % 1000; v /= 1000;
sec = v % 100; v /= 100;
min = v % 100; v /= 100;
hour = v % 100;
uint16_t msec = v % 1000U; v /= 1000U;
tm.tm_sec = v % 100U; v /= 100U;
tm.tm_min = v % 100U; v /= 100U;
tm.tm_hour = v % 100U;
int8_t rmon = mon - 2;
if (0 >= rmon) {
rmon += 12;
year -= 1;
}
// get time in seconds since unix epoch
uint32_t ret = (year/4) - (GPS_LEAPSECONDS_MILLIS / 1000UL) + 367*rmon/12 + day;
ret += year*365 + 10501;
ret = ret*24 + hour;
ret = ret*60 + min;
ret = ret*60 + sec;
// convert from time structure to unix time
time_t unix_time = AP::rtc().mktime(&tm);
// convert to time since GPS epoch
ret -= 272764785UL;
const uint32_t unix_to_GPS_secs = 315964800UL;
const uint16_t leap_seconds_unix = GPS_LEAPSECONDS_MILLIS/1000U;
uint32_t ret = unix_time + leap_seconds_unix - unix_to_GPS_secs;
// get GPS week and time
state.time_week = ret / AP_SEC_PER_WEEK;