reworked lora appserver timesync logic (part 2)
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@ -8,8 +8,10 @@
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//#define TIME_SYNC_TRIGGER 100 // threshold for time sync [milliseconds]
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#define TIME_SYNC_FRAME_LENGTH 0x07 // timeserver answer frame length [bytes]
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#define TIME_SYNC_FIXUP 4 // calibration to fixup processing time [milliseconds]
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#define TIMEREQUEST_MAX_SEQNO 0xf0 // threshold for wrap around seqno
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#define TIME_SYNC_FIXUP 16 // empirical calibration to fixup processing time [milliseconds]
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#define TIMEREQUEST_MAX_SEQNO 0xfe // threshold for wrap around seqno
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#define TIMEREQUEST_FINISH \
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(TIMEREQUEST_MAX_SEQNO + 1) // marker for end of timesync handshake
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enum timesync_t {
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timesync_tx,
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@ -19,6 +19,7 @@ static const char TAG[] = __FILE__;
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TaskHandle_t timeSyncReqTask = NULL;
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static uint8_t time_sync_seqNo = (uint8_t)random(TIMEREQUEST_MAX_SEQNO);
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static uint8_t sample_idx = 0;
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static bool timeSyncPending = false;
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static uint32_t timesync_timestamp[TIME_SYNC_SAMPLES][no_of_timestamps] = {0};
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@ -38,8 +39,12 @@ void send_timesync_req() {
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// task for sending time sync requests
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void process_timesync_req(void *taskparameter) {
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uint8_t i;
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uint32_t seq_no, time_offset_ms;
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uint32_t rcv_seq_no = TIMEREQUEST_FINISH, time_offset_ms;
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// this task is an endless loop, waiting in blocked mode, until it is
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// unblocked by send_timesync_req(). It then waits to be notified from
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// recv_timesync_ans(), which is called from RX callback in lorawan.cpp, each
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// time a timestamp from timeserver arrived.
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// --- asnychronous part: generate and collect timestamps from gateway ---
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@ -48,22 +53,23 @@ void process_timesync_req(void *taskparameter) {
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// wait for kickoff
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ulTaskNotifyTake(pdFALSE, portMAX_DELAY);
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timeSyncPending = true;
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time_offset_ms = 0;
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// wait until we are joined if we are not
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while (!LMIC.devaddr) {
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vTaskDelay(pdMS_TO_TICKS(3000));
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vTaskDelay(pdMS_TO_TICKS(5000));
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}
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// generate and collect timestamp samples
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for (i = 0; i < TIME_SYNC_SAMPLES; i++) {
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// send sync request to server
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// trigger and collect timestamp samples
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for (uint8_t i = 0; i < TIME_SYNC_SAMPLES; i++) {
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// send timesync request to timeserver
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payload.reset();
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payload.addByte(time_sync_seqNo);
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SendPayload(TIMEPORT, prio_high);
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// wait for a valid timestamp from recv_timesync_ans()
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while (seq_no != time_sync_seqNo) {
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if (xTaskNotifyWait(0x00, ULONG_MAX, &seq_no,
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// wait until recv_timesync_ans() signals a timestamp was received
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while (rcv_seq_no != time_sync_seqNo) {
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if (xTaskNotifyWait(0x00, ULONG_MAX, &rcv_seq_no,
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pdMS_TO_TICKS(TIME_SYNC_TIMEOUT * 1000)) ==
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pdFALSE) {
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ESP_LOGW(TAG, "[%0.3f] Timesync handshake error: timeout",
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@ -72,21 +78,30 @@ void process_timesync_req(void *taskparameter) {
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}
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}
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// wrap around seqNo, keeping it in time port range
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ESP_LOGD(TAG, "sample_idx = %d", sample_idx);
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// calculate time diff from collected timestamps
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time_offset_ms += timesync_timestamp[sample_idx][timesync_rx] -
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timesync_timestamp[sample_idx][timesync_tx];
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// increment and maybe wrap around seqNo, keeping it in time port range
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time_sync_seqNo++;
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if (time_sync_seqNo > TIMEREQUEST_MAX_SEQNO) {
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time_sync_seqNo = 0;
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}
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if (i < TIME_SYNC_SAMPLES - 1) {
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// wait until next cycle
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// increment index for timestamp array
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sample_idx++;
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// if last cycle, send finish char for closing timesync handshake,
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// else wait until time has come for next cycle
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if (i < TIME_SYNC_SAMPLES - 1) { // wait for next cycle
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vTaskDelay(pdMS_TO_TICKS(TIME_SYNC_CYCLE * 1000));
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} else { // before sending last time sample...
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// ...send flush to open a receive window for last time_sync_answer
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} else { // finish timesync handshake
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payload.reset();
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payload.addByte(0x99);
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payload.addByte(TIMEREQUEST_FINISH);
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SendPayload(RCMDPORT, prio_high);
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// ...send a alive open a receive window for last time_sync_answer
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// open a receive window to get last time_sync_answer instantly
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LMIC_sendAlive();
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}
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@ -97,45 +112,36 @@ void process_timesync_req(void *taskparameter) {
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// mask application irq to ensure accurate timing
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mask_user_IRQ();
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time_offset_ms = 0;
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for (i = 0; i < TIME_SYNC_SAMPLES; i++) {
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// calculate time diff from collected timestamps and apply
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// a compensation constant TIME_SYNC_FIXUP for processing time
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time_offset_ms += timesync_timestamp[i][timesync_rx] -
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timesync_timestamp[i][timesync_tx] + TIME_SYNC_FIXUP;
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}
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// decrement i for subscription to latest element in timestamp array
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i--;
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// average time offset over all collected diffs and add gateway time msec
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// average time offset over the summed up difference
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// + add msec from recent gateway time, found with last sample_idx
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// + apply a compensation constant TIME_SYNC_FIXUP for processing time
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time_offset_ms /= TIME_SYNC_SAMPLES;
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time_offset_ms += timesync_timestamp[i][gwtime_msec];
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time_offset_ms +=
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timesync_timestamp[sample_idx - 1][gwtime_msec] + TIME_SYNC_FIXUP;
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// calculate absolute time in UTC epoch: take latest time received from
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// gateway, convert to whole seconds, round to ceil, add fraction seconds
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setMyTime(timesync_timestamp[i][gwtime_sec] + time_offset_ms / 1000,
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setMyTime(timesync_timestamp[sample_idx - 1][gwtime_sec] +
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time_offset_ms / 1000,
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time_offset_ms % 1000, _lora);
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finish:
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// end of time critical section: release app irq lock
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timeSyncPending = false;
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unmask_user_IRQ();
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finish:
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timeSyncPending = false;
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} // infinite while(1)
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}
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// called from lorawan.cpp
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void store_timestamp(uint32_t timestamp, timesync_t timestamp_type) {
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uint8_t seq = time_sync_seqNo % TIME_SYNC_SAMPLES;
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timesync_timestamp[seq][timestamp_type] = timestamp;
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ESP_LOGD(TAG, "[%0.3f] seq#%d[%d]: timestamp(t%d)=%d",
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millis() / 1000.0, time_sync_seqNo, sample_idx, timestamp_type,
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timestamp);
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ESP_LOGD(TAG, "[%0.3f] Timesync seq#%d: timestamp(%d) %d stored",
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millis() / 1000.0, seq, timestamp_type, timestamp);
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timesync_timestamp[sample_idx][timestamp_type] = timestamp;
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}
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// process timeserver timestamp answer, called by myRxCallback() in lorawan.cpp
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@ -155,7 +161,7 @@ int recv_timesync_ans(const uint8_t buf[], const uint8_t buf_len) {
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if (!timeSyncPending)
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return 0; // failure
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// extract 1 byte timerequest sequence number from buffer
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// extract 1 byte timerequest sequence number from payload
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uint8_t seq_no = buf[0];
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buf++;
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@ -172,16 +178,14 @@ int recv_timesync_ans(const uint8_t buf[], const uint8_t buf_len) {
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else { // we received a probably valid time frame
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uint8_t k = seq_no % TIME_SYNC_SAMPLES;
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// pointers to 4 bytes containing UTC seconds since unix epoch, msb
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uint32_t timestamp_sec, *timestamp_ptr;
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// extract 1 byte timezone from buffer (one step being 15min * 60s = 900s)
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// extract 1 byte timezone from payload (one step being 15min * 60s = 900s)
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// uint32_t timezone_sec = buf[0] * 900; // for future use
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buf++;
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// extract 4 bytes timestamp from buffer
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// extract 4 bytes timestamp from payload
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// and convert it to uint32_t, octet order is big endian
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timestamp_ptr = (uint32_t *)buf;
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// swap byte order from msb to lsb, note: this is platform dependent
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@ -195,9 +199,8 @@ int recv_timesync_ans(const uint8_t buf[], const uint8_t buf_len) {
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// we guess timepoint is recent if it is newer than code compile date
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if (timeIsValid(t)) {
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ESP_LOGD(TAG, "[%0.3f] Timesync request #%d of %d rcvd at %0.3f",
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millis() / 1000.0, k + 1, TIME_SYNC_SAMPLES,
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osticks2ms(os_getTime()) / 1000.0);
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ESP_LOGD(TAG, "[%0.3f] Timesync request seq#%d rcvd at %0.3f",
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millis() / 1000.0, seq_no, osticks2ms(os_getTime()) / 1000.0);
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// store time received from gateway
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store_timestamp(timestamp_sec, gwtime_sec);
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