GpsMap 276C Advanced NMEA Setup
 

In the NMEA Setup of GpsMap76 and the Advanced NMEA Setup of
GpsMap276C, there is a recommendation to not select all messages to be
sent, since this could lead the time of transmission to exceeds 1 sec,
which could impact the performance of the interface with some
equipments, like autopilots.

After the 3.21 upgrade, wich included the 3 new messages (BWC, XTE and
VTG) that I have requested to be included in the Map276C, the maximum
batch would have about 16 messages like this:

$GPRMC,010003,A,1248.7047,S,03827.5797,W,0.0,94.9, 290505,23.0,W,A*03
$GPRMB,A,0.04,L,AIC,BA01,1248.4128,S,03827.6978,W, 0.314,338.4,,V,A*33
$GPGGA,010003,1248.7047,S,03827.5797,W,1,11,0.8,1. 0,M,-10.5,M,,*66
$GPGSA,A,3,01,03,06,,14,15,16,18,19,21,22,25,1.5,0 .8,1.3*3B
$GPGSV,3,1,12,01,43,333,54,03,43,237,49,06,05,030, 43,09,02,120,00*7C
$GPGSV,3,2,12,14,86,032,47,15,46,140,45,16,18,315, 47,18,19,143,49*70
$GPGSV,3,3,12,19,21,221,35,21,29,091,49,22,39,174, 43,25,17,000,50*70
$GPGLL,1248.7047,S,03827.5797,W,010003,A,A*43
$GPBOD,345.6,T,8.6,M,BA01,AIC*04
$GPBWC,010003,1248.4128,S,03827.6978,W,338.4,T,1.5 ,M,0.314,N,BA01,A*61
$GPVTG,94.9,T,117.9,M,0.0,N,0.0,K,A*19
$GPXTE,A,A,0.04,L,N,A*07
$PGRME,6.7,M,9.5,M,11.6,M*15
$PGRMZ,3,f,3*18
$PGRMM,WGS 84*06
$GPWPL,1249.4946,S,03830.9732,W,USIB*4F


This batch has 742 characters, and thus, the time to send it at 4800
bps is: 742*8/4800= 1.23 sec, which would exceed the recommended
maximum of 1 sec.

Excluding all the optional messages, as allowed in the NMEA setup,
(GSA, GSV, WPL , RME, RMZ and RMM) the batch would consist of 8
messages as follows:

$GPRMC,010003,A,1248.7047,S,03827.5797,W,0.0,94.9, 290505,23.0,W,A*03
$GPRMB,A,0.04,L,AIC,BA01,1248.4128,S,03827.6978,W, 0.314,338.4,,V,A*33
$GPGGA,010003,1248.7047,S,03827.5797,W,1,11,0.8,1. 0,M,-10.5,M,,*66
$GPGLL,1248.7047,S,03827.5797,W,010003,A,A*43
$GPBOD,345.6,T,8.6,M,BA01,AIC*04
$GPBWC,010003,1248.4128,S,03827.6978,W,338.4,T,1.5 ,M,0.314,N,BA01,A*61
$GPVTG,94.9,T,117.9,M,0.0,N,0.0,K,A*19
$GPXTE,A,A,0.04,L,N,A*07

This batch has 412 characters, and thus, the time to send it at 4800
bps is: 412*8/4800= 0.69 sec, well below the recommended maximum of 1
sec.

So, I remind the owners of Map276C to pay attention to this setup,
letting the unit send only the optional messages if needed; selecting
a batch between this two extremes would be advised.

Pascal

In article . com,
"Pascal" wrote:

This batch has 742 characters, and thus, the time to send it at 4800
bps is: 742*8/4800= 1.23 sec, which would exceed the recommended
maximum of 1 sec.

Excluding all the optional messages, as allowed in the NMEA setup,
(GSA, GSV, WPL , RME, RMZ and RMM) the batch would consist of 8
messages as follows:

$GPRMC,010003,A,1248.7047,S,03827.5797,W,0.0,94.9, 290505,23.0,W,A*03
$GPRMB,A,0.04,L,AIC,BA01,1248.4128,S,03827.6978,W, 0.314,338.4,,V,A*33
$GPGGA,010003,1248.7047,S,03827.5797,W,1,11,0.8,1. 0,M,-10.5,M,,*66
$GPGLL,1248.7047,S,03827.5797,W,010003,A,A*43
$GPBOD,345.6,T,8.6,M,BA01,AIC*04
$GPBWC,010003,1248.4128,S,03827.6978,W,338.4,T,1.5 ,M,0.314,N,BA01,A*61
$GPVTG,94.9,T,117.9,M,0.0,N,0.0,K,A*19
$GPXTE,A,A,0.04,L,N,A*07

This batch has 412 characters, and thus, the time to send it at 4800
bps is: 412*8/4800= 0.69 sec, well below the recommended maximum of 1
sec.

So, I remind the owners of Map276C to pay attention to this setup,
letting the unit send only the optional messages if needed; selecting
a batch between this two extremes would be advised.

Pascal


If you look at the data you should have noticed that the RMC Sentance
has most if not all of the information that the GLL Sentance has.
There is duplicate information in a bunch of these individual records.
RMA, RMB, and RMC, should have most everything that any NEMA Listener
should need. that's why they were designed in, as Universal Sentances.

Me

Pascal schrieb:

So, I remind the owners of Map276C to pay attention to this setup,
letting the unit send only the optional messages if needed; selecting
a batch between this two extremes would be advised.


The best option is to find out which messages your listeners need to
function properly, and only setting the absolute minimum data set.

You could as well rise the NMEA baudrate to 9600, if all your listeners
support this, but only if there is no other means to relax the 4800 baud
link. If possible, stay with the standard 4800 Baud rate, since most
listeners simply expect it to be like this.

- Carsten