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LC29H

AGNSS Fast Fix

The LC29H(AA) supports Assisted GNSS (AGNSS) to dramatically reduce cold start time from ~26 seconds to ~5 seconds by injecting satellite orbit predictions into the module before acquisition.

Two Acceleration Modes

Section titled “Two Acceleration Modes”

EASY — Self-Predicted Ephemeris

Section titled “EASY — Self-Predicted Ephemeris”

EASY (Embedded Assist System) caches the last known ephemeris and predicts satellite orbits for up to 3 days. No internet connection needed — the module generates predictions internally.

  • Enable: $PAIR490,1*3A
  • Query status: $PAIR491*3A
  • Coverage: Up to 72 hours of orbit predictions
  • Requirement: Module must have acquired a valid fix at least once

The ML1220 backup battery on the HAT maintains cached data during power-off.

EPO — Extended Prediction Orbit (Online)

Section titled “EPO — Extended Prediction Orbit (Online)”

EPO data is downloaded from Quectel/MediaTek servers and injected into the module via serial commands. Provides more accurate predictions than EASY for the first few hours.

  • Query status: $PAIR470*3A
  • Inject data: $PAIR471,<SV>,<Type>,<D0>...<D17>*CS (automated by QGNSS)
  • Erase data: $PAIR472*38
  • Coverage: Up to 72 hours

QGNSS EPO Download (Windows)

Section titled “QGNSS EPO Download (Windows)”
  1. Open QGNSS → Device → Set Device Information → Model: LC29H(AA)
  2. Select COM port (default baud: 115200)
  3. Menu → AGNSS → Assistant GNSS Offline → Connect
  4. Download EPO data to module
  5. Wait for transfer completion — the module acknowledges each segment

Cold start TTFF should now drop to approximately 5 seconds.

Time and Position Aiding

Section titled “Time and Position Aiding”

For maximum TTFF reduction, combine EPO/EASY with time and position aiding:

$PAIR590,2026,2,26,14,30,0*XX    Inject current UTC time
$PAIR600,37.7749,-122.4194,50.0*XX   Inject approximate position

Battery Backup

Section titled “Battery Backup”

The ML1220 rechargeable coin cell battery on the HAT maintains:

  • Real-time clock (RTC) for time aiding
  • SRAM-based ephemeris and almanac data
  • EASY prediction cache

When main power is removed, the battery keeps this data alive for hot starts (~1 second TTFF). If the battery is fully depleted, the module falls back to cold start behavior.