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Use exponential smoothing to predict lock time

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This commit is contained in:
Todd Herbert 2024-06-12 15:38:34 +12:00
parent 1799f6cb0f
commit 25700a1419
1 changed files with 32 additions and 19 deletions
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51
src/gps/GPS.cpp
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@ -906,22 +906,45 @@ void GPS::setAwake(bool wantAwake)
// Calculate how long it takes to get a GPS lock // Calculate how long it takes to get a GPS lock
if (wantAwake) { if (wantAwake) {
// Record the time we start looking for a lock
lastWakeStartMsec = millis(); lastWakeStartMsec = millis();
} else { } else {
// Record by how much we missed our ideal target postion.gps_update_interval (for logging only)
// Need to calculate this before we update lastSleepStartMsec, to make the new prediction
int32_t lateByMsec = (int32_t)(millis() - lastSleepStartMsec) - (int32_t)getSleepTime();
// Record the time we finish looking for a lock
lastSleepStartMsec = millis(); lastSleepStartMsec = millis();
if (GPSCycles == 1) { // Skipping initial lock time, as it will likely be much longer than average
averageLockTime = lastSleepStartMsec - lastWakeStartMsec; // How long did it take to get GPS lock this time?
} else if (GPSCycles > 1) { uint32_t lockTime = lastSleepStartMsec - lastWakeStartMsec;
averageLockTime += ((int32_t)(lastSleepStartMsec - lastWakeStartMsec) - averageLockTime) / (int32_t)GPSCycles;
// Update the lock-time prediction
// Used pre-emptively, attemtping to hit target of gps.position_update_interal
switch (GPSCycles) {
case 0:
LOG_DEBUG("Initial GPS lock took %ds\n", lockTime / 1000);
break;
case 1:
averageLockTime = lockTime; // Avoid slow ramp-up - start with a real value
LOG_DEBUG("GPS Lock took %ds\n", lockTime / 1000);
break;
default:
// Predict lock-time using exponential smoothing: respond slowly to changes
averageLockTime = (lockTime * 0.2) + (averageLockTime * 0.8); // Latest lock time has 20% weight on prediction
LOG_INFO("GPS Lock took %ds. %s by %ds. Next lock predicted to take %ds.\n", lockTime / 1000,
(lateByMsec > 0) ? "Late" : "Early", abs(lateByMsec) / 1000, averageLockTime / 1000);
} }
GPSCycles++; GPSCycles++;
LOG_DEBUG("GPS Lock took %d, average %d\n", (lastSleepStartMsec - lastWakeStartMsec) / 1000, averageLockTime / 1000);
} }
// How long to wait before attempting next GPS update
// Aims to hit position.gps_update_interval by using the lock-time prediction
uint32_t compensatedSleepTime = (getSleepTime() > averageLockTime) ? (getSleepTime() - averageLockTime) : 0;
// If long interval between updates: power off between updates // If long interval between updates: power off between updates
if ((int32_t)getSleepTime() - averageLockTime > GPS_STANDBY_THRESHOLD_MINUTES * MS_IN_MINUTE) { if (compensatedSleepTime > GPS_STANDBY_THRESHOLD_MINUTES * MS_IN_MINUTE) {
setGPSPower(wantAwake, false, getSleepTime() - averageLockTime); setGPSPower(wantAwake, false, getSleepTime() - averageLockTime);
return;
} }
// If waking relatively frequently: don't power off. Would use more energy trying to reacquire lock each time // If waking relatively frequently: don't power off. Would use more energy trying to reacquire lock each time
@ -929,21 +952,11 @@ void GPS::setAwake(bool wantAwake)
// Will decide which inside setGPSPower method // Will decide which inside setGPSPower method
else { else {
#ifdef GPS_UC6580 #ifdef GPS_UC6580
setGPSPower(wantAwake, false, getSleepTime() - averageLockTime); setGPSPower(wantAwake, false, compensatedSleepTime);
#else #else
setGPSPower(wantAwake, true, getSleepTime() - averageLockTime); setGPSPower(wantAwake, true, compensatedSleepTime);
#endif #endif
return;
} }
// Gradually recover from an abnormally long "time to get lock"
if (averageLockTime > 20000) {
averageLockTime -= 1000; // eventually want to sleep again.
}
// Make sure we don't have a fallthrough where GPS is stuck off
if (wantAwake)
setGPSPower(true, true, 0);
} }
} }