243 lines
8.0 KiB
C++
243 lines
8.0 KiB
C++
/*
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///--> IMPORTANT LICENSE NOTE for this file <--///
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PLEASE NOTE: There is a patent filed for the time sync algorithm used in the
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code of this file. The shown implementation example is covered by the
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repository's licencse, but you may not be eligible to deploy the applied
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algorithm in applications without granted license by the patent holder.
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*/
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#if (TIME_SYNC_LORASERVER) && (HAS_LORA)
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#include "timesync.h"
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// Local logging tag
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static const char TAG[] = __FILE__;
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using namespace std::chrono;
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typedef std::chrono::system_clock myClock;
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typedef myClock::time_point myClock_timepoint;
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typedef std::chrono::duration<long long int, std::ratio<1, 1000>>
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myClock_msecTick;
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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 bool timeSyncPending = false;
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static myClock_timepoint time_sync_tx[TIME_SYNC_SAMPLES];
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static myClock_timepoint time_sync_rx[TIME_SYNC_SAMPLES];
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// send time request message
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void send_timesync_req() {
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// if a timesync handshake is pending then exit
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if (timeSyncPending)
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return;
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// else unblock timesync task
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else {
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ESP_LOGI(TAG, "[%0.3f] Timeserver sync request started", millis() / 1000.0);
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xTaskNotifyGive(timeSyncReqTask);
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}
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}
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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 k;
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uint16_t time_to_set_fraction_msec;
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uint32_t seq_no = 0, time_to_set;
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auto time_offset_ms = myClock_msecTick::zero();
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while (1) {
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// reset all timestamps before next sync run
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time_offset_ms = myClock_msecTick::zero();
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for (uint8_t i = 0; i < TIME_SYNC_SAMPLES; i++)
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time_sync_tx[i] = time_sync_rx[i] = myClock_timepoint();
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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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// 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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}
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// collect timestamp samples
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for (uint8_t i = 0; i < TIME_SYNC_SAMPLES; i++) {
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// send sync request to server
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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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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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millis() / 1000.0);
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goto finish; // no valid sequence received before timeout
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}
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}
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// process answer
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k = seq_no % TIME_SYNC_SAMPLES;
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// calculate time diff from collected timestamps
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time_offset_ms += time_point_cast<milliseconds>(time_sync_rx[k]) -
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time_point_cast<milliseconds>(time_sync_tx[k]);
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// 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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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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payload.reset();
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payload.addByte(0x99);
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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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LMIC_sendAlive();
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}
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} // end of for loop to collect timestamp samples
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// mask application irq to ensure accurate timing
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mask_user_IRQ();
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// average time offset over all collected diffs
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time_offset_ms /= TIME_SYNC_SAMPLES;
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// calculate time offset with millisecond precision using LMIC's time base,
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// since we use LMIC's ostime_t txEnd as tx timestamp.
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// Also apply calibration const to compensate processing time.
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time_offset_ms += milliseconds(osticks2ms(os_getTime())) -
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milliseconds(millis()) + milliseconds(TIME_SYNC_FIXUP);
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// calculate absolute time in UTC epoch: convert to whole seconds, round to
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// ceil, and calculate fraction milliseconds
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time_to_set = (uint32_t)(time_offset_ms.count() / 1000) + 1;
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// calculate fraction milliseconds
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time_to_set_fraction_msec = (uint16_t)(time_offset_ms.count() % 1000);
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setMyTime(time_to_set, time_to_set_fraction_msec, _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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} // infinite while(1)
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}
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// called from lorawan.cpp after time_sync_req was sent
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void store_time_sync_req(uint32_t timestamp) {
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// if no timesync handshake is pending then exit
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if (!timeSyncPending)
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return;
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uint8_t k = time_sync_seqNo % TIME_SYNC_SAMPLES;
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time_sync_tx[k] += milliseconds(timestamp);
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ESP_LOGD(TAG, "[%0.3f] Timesync request #%d of %d sent at %d.%03d",
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millis() / 1000.0, k + 1, TIME_SYNC_SAMPLES, timestamp / 1000,
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timestamp % 1000);
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}
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// process timeserver timestamp answer, called by myRxCallback() in lorawan.cpp
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int recv_timesync_ans(const uint8_t buf[], const uint8_t buf_len) {
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/*
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parse 7 byte timesync_answer:
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byte meaning
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1 sequence number (taken from node's time_sync_req)
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2 timezone in 15 minutes steps
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3..6 current second (from epoch time 1970)
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7 1/250ths fractions of current second
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*/
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// if no timesync handshake is pending then exit
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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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uint8_t seq_no = buf[0];
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buf++;
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// if no time is available or spurious buffer then exit
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if (buf_len != TIME_SYNC_FRAME_LENGTH) {
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if (seq_no == 0xff)
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ESP_LOGI(TAG, "[%0.3f] Timeserver error: no confident time available",
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millis() / 1000.0);
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else
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ESP_LOGW(TAG, "[%0.3f] Timeserver error: spurious data received",
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millis() / 1000.0);
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return 0; // failure
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}
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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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// 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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// 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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timestamp_sec = __builtin_bswap32(*timestamp_ptr);
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buf += 4;
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// extract 1 byte fractional seconds in 2^-8 second steps
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// (= 1/250th sec), we convert this to ms
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uint16_t timestamp_msec = 4 * buf[0];
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// construct the timepoint when message was seen on gateway
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time_sync_rx[k] += seconds(timestamp_sec) + milliseconds(timestamp_msec);
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// we guess timepoint is recent if it is newer than code compile date
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if (timeIsValid(myClock::to_time_t(time_sync_rx[k]))) {
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ESP_LOGD(TAG, "[%0.3f] Timesync request #%d of %d rcvd at %d.%03d",
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millis() / 1000.0, k + 1, TIME_SYNC_SAMPLES, timestamp_sec,
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timestamp_msec);
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// inform processing task
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xTaskNotify(timeSyncReqTask, seq_no, eSetBits);
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return 1; // success
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} else {
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ESP_LOGW(TAG, "[%0.3f] Timeserver error: outdated time received",
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millis() / 1000.0);
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return 0; // failure
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}
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}
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}
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// create task for timeserver handshake processing, called from main.cpp
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void timesync_init() {
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xTaskCreatePinnedToCore(process_timesync_req, // task function
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"timesync_req", // name of task
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2048, // stack size of task
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(void *)1, // task parameter
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3, // priority of the task
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&timeSyncReqTask, // task handle
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1); // CPU core
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}
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#endif
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