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reworked lora appserver timesync logic (part 1)

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This commit is contained in:
Klaus K Wilting 2020-03-03 12:54:42 +01:00
parent 0f2e48f39c
commit 1516d71018
2 changed files with 54 additions and 66 deletions
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12
include/timesync.h
View File

@ -11,12 +11,18 @@
#define TIME_SYNC_FIXUP 4 // calibration to fixup processing time [milliseconds] #define TIME_SYNC_FIXUP 4 // calibration to fixup processing time [milliseconds]
#define TIMEREQUEST_MAX_SEQNO 0xf0 // threshold for wrap around seqno #define TIMEREQUEST_MAX_SEQNO 0xf0 // threshold for wrap around seqno
enum timesync_t {
timesync_tx,
timesync_rx,
gwtime_sec,
gwtime_msec,
no_of_timestamps
};
void timesync_init(void); void timesync_init(void);
void send_timesync_req(void); void send_timesync_req(void);
int recv_timesync_ans(const uint8_t buf[], uint8_t buf_len); int recv_timesync_ans(const uint8_t buf[], uint8_t buf_len);
void process_timesync_req(void *taskparameter); void process_timesync_req(void *taskparameter);
void store_time_sync_req(uint32_t t_millisec); void store_timestamp(uint32_t timestamp, timesync_t timestamp_type);
#endif #endif

108
src/timesync.cpp
View File

@ -16,19 +16,11 @@ algorithm in applications without granted license by the patent holder.
// Local logging tag // Local logging tag
static const char TAG[] = __FILE__; static const char TAG[] = __FILE__;
using namespace std::chrono;
typedef std::chrono::system_clock myClock;
typedef myClock::time_point myClock_timepoint;
typedef std::chrono::duration<long long int, std::ratio<1, 1000>>
myClock_msecTick;
TaskHandle_t timeSyncReqTask = NULL; TaskHandle_t timeSyncReqTask = NULL;
static uint8_t time_sync_seqNo = (uint8_t)random(TIMEREQUEST_MAX_SEQNO); static uint8_t time_sync_seqNo = (uint8_t)random(TIMEREQUEST_MAX_SEQNO);
static bool timeSyncPending = false; static bool timeSyncPending = false;
static myClock_timepoint time_sync_tx[TIME_SYNC_SAMPLES]; static uint32_t timesync_timestamp[TIME_SYNC_SAMPLES][no_of_timestamps] = {0};
static myClock_timepoint time_sync_rx[TIME_SYNC_SAMPLES];
// send time request message // send time request message
void send_timesync_req() { void send_timesync_req() {
@ -46,18 +38,13 @@ void send_timesync_req() {
// task for sending time sync requests // task for sending time sync requests
void process_timesync_req(void *taskparameter) { void process_timesync_req(void *taskparameter) {
uint8_t k; uint8_t i;
uint16_t time_to_set_fraction_msec; uint32_t seq_no, time_offset_ms;
uint32_t seq_no = 0, time_to_set;
auto time_offset_ms = myClock_msecTick::zero(); // --- asnychronous part: generate and collect timestamps from gateway ---
while (1) { while (1) {
// reset all timestamps before next sync run
time_offset_ms = myClock_msecTick::zero();
for (uint8_t i = 0; i < TIME_SYNC_SAMPLES; i++)
time_sync_tx[i] = time_sync_rx[i] = myClock_timepoint();
// wait for kickoff // wait for kickoff
ulTaskNotifyTake(pdFALSE, portMAX_DELAY); ulTaskNotifyTake(pdFALSE, portMAX_DELAY);
timeSyncPending = true; timeSyncPending = true;
@ -67,8 +54,8 @@ void process_timesync_req(void *taskparameter) {
vTaskDelay(pdMS_TO_TICKS(3000)); vTaskDelay(pdMS_TO_TICKS(3000));
} }
// collect timestamp samples // generate and collect timestamp samples
for (uint8_t i = 0; i < TIME_SYNC_SAMPLES; i++) { for (i = 0; i < TIME_SYNC_SAMPLES; i++) {
// send sync request to server // send sync request to server
payload.reset(); payload.reset();
payload.addByte(time_sync_seqNo); payload.addByte(time_sync_seqNo);
@ -85,13 +72,6 @@ void process_timesync_req(void *taskparameter) {
} }
} }
// process answer
k = seq_no % TIME_SYNC_SAMPLES;
// calculate time diff from collected timestamps
time_offset_ms += time_point_cast<milliseconds>(time_sync_rx[k]) -
time_point_cast<milliseconds>(time_sync_tx[k]);
// wrap around seqNo, keeping it in time port range // wrap around seqNo, keeping it in time port range
time_sync_seqNo++; time_sync_seqNo++;
if (time_sync_seqNo > TIMEREQUEST_MAX_SEQNO) { if (time_sync_seqNo > TIMEREQUEST_MAX_SEQNO) {
@ -109,32 +89,36 @@ void process_timesync_req(void *taskparameter) {
// ...send a alive open a receive window for last time_sync_answer // ...send a alive open a receive window for last time_sync_answer
LMIC_sendAlive(); LMIC_sendAlive();
} }
} // end of for loop to collect timestamp samples } // end of for loop to collect timestamp samples
// --- time critial part: evaluate timestamps and calculate time ---
// mask application irq to ensure accurate timing // mask application irq to ensure accurate timing
mask_user_IRQ(); mask_user_IRQ();
// average time offset over all collected diffs time_offset_ms = 0;
for (i = 0; i < TIME_SYNC_SAMPLES; i++) {
// calculate time diff from collected timestamps and apply
// a compensation constant TIME_SYNC_FIXUP for processing time
time_offset_ms += timesync_timestamp[i][timesync_rx] -
timesync_timestamp[i][timesync_tx] + TIME_SYNC_FIXUP;
}
// decrement i for subscription to latest element in timestamp array
i--;
// average time offset over all collected diffs and add gateway time msec
time_offset_ms /= TIME_SYNC_SAMPLES; time_offset_ms /= TIME_SYNC_SAMPLES;
time_offset_ms += timesync_timestamp[i][gwtime_msec];
// --------- do we need this? --------- // calculate absolute time in UTC epoch: take latest time received from
// calculate time offset with millisecond precision using LMIC's time base, // gateway, convert to whole seconds, round to ceil, add fraction seconds
// since we use LMIC's ostime_t txEnd as tx timestamp.
//
// time_offset_ms += milliseconds(osticks2ms(os_getTime())) -
// milliseconds(millis());
// --------- not sure -----------------
// Apply calibration const to compensate processing time. setMyTime(timesync_timestamp[i][gwtime_sec] + time_offset_ms / 1000,
time_offset_ms += milliseconds(TIME_SYNC_FIXUP); time_offset_ms % 1000, _lora);
// calculate absolute time in UTC epoch: convert to whole seconds, round
// to ceil, and calculate fraction milliseconds
time_to_set = (uint32_t)(time_offset_ms.count() / 1000) + 1;
// calculate fraction milliseconds
time_to_set_fraction_msec = (uint16_t)(time_offset_ms.count() % 1000);
setMyTime(time_to_set, time_to_set_fraction_msec, _lora);
finish: finish:
// end of time critical section: release app irq lock // end of time critical section: release app irq lock
@ -144,19 +128,14 @@ void process_timesync_req(void *taskparameter) {
} // infinite while(1) } // infinite while(1)
} }
// called from lorawan.cpp after time_sync_req was sent // called from lorawan.cpp
void store_time_sync_req(uint32_t timestamp) { void store_timestamp(uint32_t timestamp, timesync_t timestamp_type) {
// if no timesync handshake is pending then exit uint8_t seq = time_sync_seqNo % TIME_SYNC_SAMPLES;
if (!timeSyncPending) timesync_timestamp[seq][timestamp_type] = timestamp;
return;
uint8_t k = time_sync_seqNo % TIME_SYNC_SAMPLES; ESP_LOGD(TAG, "[%0.3f] Timesync seq#%d: timestamp(%d) %d stored",
time_sync_tx[k] += milliseconds(timestamp); millis() / 1000.0, seq, timestamp_type, timestamp);
ESP_LOGD(TAG, "[%0.3f] Timesync request #%d of %d sent at %d.%03d",
millis() / 1000.0, k + 1, TIME_SYNC_SAMPLES, timestamp / 1000,
timestamp % 1000);
} }
// process timeserver timestamp answer, called by myRxCallback() in lorawan.cpp // process timeserver timestamp answer, called by myRxCallback() in lorawan.cpp
@ -211,15 +190,18 @@ int recv_timesync_ans(const uint8_t buf[], const uint8_t buf_len) {
// extract 1 byte fractional seconds in 2^-8 second steps // extract 1 byte fractional seconds in 2^-8 second steps
// (= 1/250th sec), we convert this to ms // (= 1/250th sec), we convert this to ms
uint16_t timestamp_msec = 4 * buf[0]; uint16_t timestamp_msec = 4 * buf[0];
// calculate absolute time received from gateway
// construct the timepoint when message was seen on gateway time_t t = timestamp_sec + timestamp_msec / 1000;
time_sync_rx[k] += seconds(timestamp_sec) + milliseconds(timestamp_msec);
// we guess timepoint is recent if it is newer than code compile date // we guess timepoint is recent if it is newer than code compile date
if (timeIsValid(myClock::to_time_t(time_sync_rx[k]))) { if (timeIsValid(t)) {
ESP_LOGD(TAG, "[%0.3f] Timesync request #%d of %d rcvd at %d.%03d", ESP_LOGD(TAG, "[%0.3f] Timesync request #%d of %d rcvd at %0.3f",
millis() / 1000.0, k + 1, TIME_SYNC_SAMPLES, timestamp_sec, millis() / 1000.0, k + 1, TIME_SYNC_SAMPLES,
timestamp_msec); osticks2ms(os_getTime()) / 1000.0);
// store time received from gateway
store_timestamp(timestamp_sec, gwtime_sec);
store_timestamp(timestamp_msec, gwtime_msec);
// inform processing task // inform processing task
xTaskNotify(timeSyncReqTask, seq_no, eSetBits); xTaskNotify(timeSyncReqTask, seq_no, eSetBits);