Lantronix PNT Series PNT-SG3FS GNSS Module Software User Guide - Page 46

5. Assisted GNSS Then the almanacs can be injected into the device using the $PSTMALMANAC command for each satellite(between two consecutive commands there must be at least a 20-millisecond delay). Now the device will be capable of achieving the fix very quickly if enough satellites are in view. Password Generation As mentioned, in order to access the RxNetworks servers, the user has to provide a set of parameters which are used in generating the HTTP request. These parameters are used to generate a password string (up to 41 characters in length) that is required by the HTTP request string. GNSS device provides the $PSTMSTAGPS8PASSGEN NMEA command that performs the password generation. The user must supply three parameters to this command that will be used to generate a unique password. In order to generate the password the user must pass the following parameters: ♦ The current time expressed as GPS seconds (i.e., the number of seconds since midnight 06-Jan-1980) ♦ The vendor id string (RxNetworks refers to as customer ID; see cId in Appendix B) ♦ The model id string (RxNetworks refers to as model ID; see mId in Appendix B) The device id and password strings will be returned in response to the password generation NMEA command in a $PSTMSTAGPS8PASSRTN NMEA message. The parameters provided can be used to access the RxNetworks location.io service (refer to Section 4.1 in ST Microelectronics Application Note "AN5160: RxNetworks Assisted GNSS Server Interface Specification"). Real-Time Assistance Data Uploading Procedure The real-time AGNSS performances depend on the availability of a network connection in order to download assistance data, which include: ♦ The current time (if not available, from instance, from RTC) ♦ The ephemerides ♦ The almanacs ♦ The rough position (optional) Once those data have been downloaded from the server, the first thing to do is to inject the current time into thedevice (if the device has no RTC, or if it is set to the wrong time). This can be done either using the $PSTMINITTIME command or, if the approximate position is available, then both current time and position can be injected using the $PSTMINITGPS command. Then the ephemerides can be injected into the device using the $PSTMEPHEM command for each satellite (between two consecutive commands there must be at least a 20-millisecond delay). Then the almanacs can be injected into the device using the $PSTMALMANAC command for each satellite (between two consecutive commands there must be at least a 20-millisecond delay). Now the device will be capable of achieving the fix very quickly if enough satellites are in view. PNT-SG3FS GNSS Module Software User Guide 46