reworked lora appserver timesync logic (part 1)
This commit is contained in:
Klaus K Wilting
parent
0f2e48f39c
commit
1516d71018
@ -11,12 +11,18 @@
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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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enum timesync_t {
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timesync_tx,
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timesync_rx,
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gwtime_sec,
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gwtime_msec,
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no_of_timestamps
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};
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void timesync_init(void);
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void send_timesync_req(void);
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int recv_timesync_ans(const uint8_t buf[], uint8_t buf_len);
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void process_timesync_req(void *taskparameter);
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void store_time_sync_req(uint32_t t_millisec);
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void store_timestamp(uint32_t timestamp, timesync_t timestamp_type);
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#endif
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108
src/timesync.cpp
108
src/timesync.cpp
@ -16,19 +16,11 @@ algorithm in applications without granted license by the patent holder.
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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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static uint32_t timesync_timestamp[TIME_SYNC_SAMPLES][no_of_timestamps] = {0};
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// send time request message
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void send_timesync_req() {
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@ -46,18 +38,13 @@ 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 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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uint8_t i;
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uint32_t seq_no, time_offset_ms;
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// --- asnychronous part: generate and collect timestamps from gateway ---
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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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@ -67,8 +54,8 @@ void process_timesync_req(void *taskparameter) {
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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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// 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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payload.reset();
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payload.addByte(time_sync_seqNo);
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@ -85,13 +72,6 @@ void process_timesync_req(void *taskparameter) {
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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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@ -109,32 +89,36 @@ void process_timesync_req(void *taskparameter) {
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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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// --- time critial part: evaluate timestamps and calculate time ---
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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 = 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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time_offset_ms /= TIME_SYNC_SAMPLES;
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time_offset_ms += timesync_timestamp[i][gwtime_msec];
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// --------- do we need this? ---------
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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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//
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// time_offset_ms += milliseconds(osticks2ms(os_getTime())) -
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// milliseconds(millis());
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// --------- not sure -----------------
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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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// Apply calibration const to compensate processing time.
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time_offset_ms += milliseconds(TIME_SYNC_FIXUP);
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// calculate absolute time in UTC epoch: convert to whole seconds, round
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// to 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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setMyTime(timesync_timestamp[i][gwtime_sec] + 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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@ -144,19 +128,14 @@ void process_timesync_req(void *taskparameter) {
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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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// called from lorawan.cpp
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void store_timestamp(uint32_t timestamp, timesync_t timestamp_type) {
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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 seq = time_sync_seqNo % TIME_SYNC_SAMPLES;
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timesync_timestamp[seq][timestamp_type] = timestamp;
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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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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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}
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// process timeserver timestamp answer, called by myRxCallback() in lorawan.cpp
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@ -211,15 +190,18 @@ int recv_timesync_ans(const uint8_t buf[], const uint8_t buf_len) {
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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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// calculate absolute time received from gateway
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time_t t = timestamp_sec + timestamp_msec / 1000;
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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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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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// store time received from gateway
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store_timestamp(timestamp_sec, gwtime_sec);
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store_timestamp(timestamp_msec, gwtime_msec);
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// inform processing task
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xTaskNotify(timeSyncReqTask, seq_no, eSetBits);
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