Lantronix PNT Series PNT-SG3FS GNSS Module Software User Guide - Page 54

10. Low Power Modes Adaptive and Cyclic Mode State Diagram The library, using the Estimated Horizontal Position Error (EHPE), implements a dynamic constellation switch, in this way the device is able to optimize the usage of multi-constellation satellites allowing the customer to select the proper compromise between accuracy performance and power consumption. EHPE is a measure of the error in a GNSS position on the horizontal plane. This value can be monitored in the NMEA sentences $GPGST. Figure 17 below shows the algorithm's state diagram. Figure 17: Adaptive and Cyclic Mode State Diagram The Adaptive and Cyclic Low Power algorithm is scheduled every second. Initial state is achieved only after the steady state is reached. The steady state in GNSS mode is a particular condition in which the software turns off the acquisition engine. This condition is reached when all the following conditions are true: ♦ The system is in Position Accurate condition (position fix available) ♦ Ephemeris available (4 for GPS, 4 for GLONASS) ♦ Almanac completely downloaded Generally at first start up (Full Cold Mode) this condition, in full sky is reached in 12.5 minutes. Diagram explanations in Table 15 below: Table 15. Adaptive and Cyclic Finite State Machine Description State INITIAL_STATE FULL_CONST Description o All the GNSS constellations enabled in the firmware-configuration are active during the runtime o System fully running. Next State FULL_CONST only when all the three conditions are taken: o position fix available o almanac completely downloaded o ephemeris available (4 for GPS, 4 for GLONASS); LOW_POWER_STATE only if EHPE average is less than EHPE threshold (good sky condition) PNT-SG3FS GNSS Module Software User Guide 54