Hal Murray wrote: > It would be really neat if you could run similar experiments on 3.3 and/or > 3.5.
I have run some more tests Hal, with V3.5, averaging ON and OFF. I include V3.2 for comparison. I measured the time of the "START" character ($) of the $GPRMC sentence and the "LAST" 0x10 (Linefeed) character, relative to the leading transition of the 1PPS, GPS 18x set to 4800 Baud. Version 3.20 firmware for Garmin 18x START Min = 370 START Avg = 433 (N = 7200) START Max = 518 LAST Min = 519 LAST Avg = 582 (N = 7200) LAST Max = 667 Version 3.50 firmware for Garmin 18x with Averaging ON START Min = 768 START Avg = 813 (N = 4194) START Max = 871 LAST Min = 917 LAST Avg = 962 (N = 4194) LAST Max = 1020 ( 7 sentences finished over 1,000 ms) Version 3.50 firmware for Garmin 18x with Averaging OFF START Min = 769 START Avg = 805 (N = 3563) START Max = 858 LAST Min = 918 LAST Avg = 954 (N = 3563) LAST Max = 1007 ( 4 sentences finished over 1,000 ms) This agrees with what Kasper Pedersen wrote earlier: > 3.10 starts transmitting 350ms .. 480ms after PPS > 3.30 starts transmitting 920ms .. 1220ms (!) after PPS > 3.50 starts transmitting 700ms .. 1220ms (!) after PPS The "averaging" appears to have about an 8 ms penalty in delaying the NMEA data stream. We can see in the above, that V3.5 RMC is infrequently not finishing "within" the correct second ! For "my" application I need both RMC and GGA to finish within the current second - which the Garmin 18x does very comfortably with version 3.2 and under. Kevin Rosenberg wrote: > Has anyone had trouble with reverting firmware upgrades on > Garmin products? Of course, feedback on going back from > 3.50 to 3.20 on an 18x would be most specific to my situation. I have "reverted" quite a number of times now Kevin - trying to understand why the 18x can be 1 second slow. I have never had an issue putting in an older version into the 18x, the updater software does know what your doing, it says: "Your current software version is newer than the update version. Do you want to replace your current software version with an older version ? " We click the YES box. To do the above timing tests I had v3.5 loaded into my 18x, I then reverted to v3.2 and everything worked fine Kevin (to answer your specific question). Regards, Kiwi Geoff (New Zealand). _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.