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GSV cycle time on MTK-3301

From: Sanjeev Gupta
Subject: GSV cycle time on MTK-3301
Date: Mon, 14 Nov 2022 14:52:42 +0800


I have an MTK-3301 (Surefilre), running for about 10 years, on a Linux x64.
gpsd: 3.24.1~dev (revision release-3.24-295-g327b57968)

A few months ago, I noticed the gpsd.php
had stopped showing the Skymap.  I assumed that this was a PHP or something error, and never got round to debugging it.

I did notice that if I pressed Refresh, etc, I would get flashes (once in a dozen times) of the Skymap.

Today, I re-read on the ?WATCH command, and noticed the GPGSV was appearing only every 5 cycles.  So this behaviour is understandable.

Would it be better for gpsd.php to *not* clear the skymap on each cycle?  Or might that give false, stale, results?

Alternatively, drivers/drivers.c, lines 1027ff:

NMEA_SEN_GLL,  GPGLL   interval - Geographic Position - Latitude longitude
NMEA_SEN_RMC,  GPRMC   interval - Recommended Minimum Specific GNSS Sentence
NMEA_SEN_VTG,  GPVTG   interval - Course Over Ground and Ground Speed
NMEA_SEN_GGA,  GPGGA   interval - GPS Fix Data
NMEA_SEN_GSA,  GPGSA   interval - GNSS DOPS and Active Satellites
NMEA_SEN_GSV,  GPGSV   interval - GNSS Satellites in View
NMEA_SEN_GRS,  GPGRS   interval - GNSS Range Residuals
NMEA_SEN_GST,  GPGST   interval - GNSS Pseudorange Errors Statistics
NMEA_SEN_MALM, PMTKALM interval - GPS almanac information
NMEA_SEN_MEPH, PMTKEPH interval - GPS ephemeris information
NMEA_SEN_MDGP, PMTKDGP interval - GPS differential correction information
NMEA_SEN_MDBG, PMTKDBG interval – MTK debug information
NMEA_SEN_ZDA,  GPZDA   interval - Time & Date
NMEA_SEN_MCHN, PMTKCHN interval – GPS channel status
// MTK 3333
NMEA_SEN_DTM,  GPDTM   interval - Datum reference


I see the "5" there clearly.

I tried using gpsctl, to send:
but that does not change anything

Sanjeev Gupta
+65 98551208

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