NMEA 0183 sentence for barometric pressure

[richarddaneel]

Good day all, sorry about the newbie question but the dashboard has a barometric pressure dial, however, according to the user manual the only sentences recognised by OpenCPN is:

The Dashboard Plugin recognises the following input NMEA sentences:
DBT - Depth Below Transducer
DPT - Depth of Water
GGA - Global Positioning System Fix Data
GLL - Geographic Position - Latitude/Longitude HDG Heading - Deviation & Variation
HDM - Heading - Magnetic
HDT - Heading - True
MTA - Air Temperature (obsolete)
MDA - Meteorological Composite (obsolete)
MTW - Mean Temperature of Water
VLW - Distance Traveled through Water
MWD - Wind Direction & Speed
MWV - Wind Speed and Angle
RMC - Recommended Minimum Navigation Information
RSA - Rudder Sensor Angle
VHW - Water speed and heading
VTG - Track made good and Ground speed
VWR - Relative Wind Speed and Angle
VWT - True Windspeed and Angle (obsolete)
ZDA -Time & Date - UTC, day, month, year and local time zone
AIVDO - Automatic Information System (AIS) position reports from own vessel


Does anyone know the format of the nmea 0183 sentence for the barometric pressure side, any help greatly appreciates. lastly, is it OK to send an answer to my email address?? Richard at sprs dot co dot za ?????

many thanks

[Paul Elliott]

The recommended NMEA0183 sentence is "XDR". The website "NMEA Revealed" has a decent listing (NMEA Revealed).

For pressure, the Type Field is "P".
The units are "B" for Bars, or "P" for Pascals.

You will see other non-standard NMEA spec lists claim that XDR is a crosstrack error sentence, but this is wrong.

[Paul Elliott]

Here's a more complete listing from http://edu-observatory.org/gps/NMEA_0183.txt

XDR - Transducer Measurements

Measurement data from transducers that measure physical quantities
such as temperature, force, pressure, frequency, angular or linear
displacement, etc. Data from a variable number transducers measuring
the same or different quantities can be mixed in the same sentence.
This sentence is designed for use by integrated systems as well as
transducers that may be connected in a 'chain' where each transducer
receives the sentence as an input and adds its own data fields on
before retransmitting the sentence.

$--XDR,a,x.x,a,c--c, ________ ...
| | | | |
| | | | +---------Data for variable # of transducers
| | | +----------------\Transducer #1 ID
| | +-------------------|Units of measure, Transducer #1 [2]
| +----------------------|Measurement data, Transducer #1
+-------------------------/Transducer type, Transducer #1 [2]


a,x.x,a,c--c*hh<CR><LF>
| | | |
| | | +--------------------\
| | +-----------------------|
| +--------------------------|
+-----------------------------/Transducer 'n' [1]


Notes:

[1] Sets of the four fields 'Type-Data-Units-ID' are allowed for an unde-
fined number of transducers. Up to 'n' transducers may be included
within the limits of allowed sentence length, null fields are not re-
quired except where portions of the 'Type-Data-Units-ID' combination are
not available.

[2] Allowed transducer types and their units of measure are:

Transducer Type Field Units Field Comments

temperature C C = degrees Celsius
angular displacement A D = degrees "-" = anticlockwise
linear displacement D M = meters "-" = compression
frequency F H = Hertz
force N N = Newtons "-" = compression
pressure P B = Bars "-" = vacuum
flow rate R l = liters/second
tachometer T R = RPM
humidity H P = Percent
volume V M = cubic meters

[transmitterdan]

Originally Posted by richarddaneel

Good day all, sorry about the newbie question but the dashboard has a barometric pressure dial, however, according to the user manual the only sentences recognised by OpenCPN is:

The Dashboard Plugin recognises the following input NMEA sentences:
DBT - Depth Below Transducer
DPT - Depth of Water
GGA - Global Positioning System Fix Data
GLL - Geographic Position - Latitude/Longitude HDG Heading - Deviation & Variation
HDM - Heading - Magnetic
HDT - Heading - True
MTA - Air Temperature (obsolete)
MDA - Meteorological Composite (obsolete)
MTW - Mean Temperature of Water
VLW - Distance Traveled through Water
MWD - Wind Direction & Speed
MWV - Wind Speed and Angle
RMC - Recommended Minimum Navigation Information
RSA - Rudder Sensor Angle
VHW - Water speed and heading
VTG - Track made good and Ground speed
VWR - Relative Wind Speed and Angle
VWT - True Windspeed and Angle (obsolete)
ZDA -Time & Date - UTC, day, month, year and local time zone
AIVDO - Automatic Information System (AIS) position reports from own vessel


Does anyone know the format of the nmea 0183 sentence for the barometric pressure side, any help greatly appreciates. lastly, is it OK to send an answer to my email address?? Richard at sprs dot co dot za ?????

many thanks

Looking at the source code I believe O gets barometric pressure from the MDA sentence.

If XDR is a better source then a flyspray tracker request at http://willkamp.opencpn/flyspray/ would be appreciated.

[Paul Elliott]

MDA, and a few other weather-related sentences are listed (with specs) in the "NMEA 0183 Sentences Not Recommended for New Designs" document: http://www.nmea.org/Assets/100108_nm...ew_designs.pdf

NMEA is recommending that XDR be used. I'm not involved with the OCPN project, other than as an interested user. Also, I can't get that flyspray link to work. Can someone else make the request?

[transmitterdan]

Originally Posted by Paul Elliott

MDA, and a few other weather-related sentences are listed (with specs) in the "NMEA 0183 Sentences Not Recommended for New Designs" document: http://www.nmea.org/Assets/100108_nm...ew_designs.pdf

NMEA is recommending that XDR be used. I'm not involved with the OCPN project, other than as an interested user. Also, I can't get that flyspray link to work. Can someone else make the request?

Paul,

I can do it. Sorry, the link I gave was bad. It should be http://willkamp.com/opencpn/flyspray/ and you have to sign up to be able to add feature requests.

I have a few NMEA streams and the few that I have with baro data have it in the MDA sentence.

I have an online repository of NMEA test streams. If you have any streams that make use of the XDR sentence structure I would love to add them to that repository. We use the files to test OpenCPN so the more variety of data streams we have the better. In fact, any NMEA data files you can share that could be put in the test repository would really help to improve OpenCPN.

Edit: There is an entry in flyspray about this issue. I'll try to follow up and see what can be done.

[richarddaneel]

Thanks ever so much for your replies. I have attached a pic of the NMEA Debug window. I have formatted the code too print out the sentence as suggested (the WIXDR one), however the Barometer still does not recognise it while the GPS side works fantastically. Any further help will be greatly appreciated.

richard

[transmitterdan]

Originally Posted by richarddaneel

Thanks ever so much for your replies. I have attached a pic of the NMEA Debug window. I have formatted the code too print out the sentence as suggested (the WIXDR one), however the Barometer still does not recognise it while the GPS side works fantastically. Any further help will be greatly appreciated.

richard

Richard,

If you want the present day version of OpenCPN to display barometric data you will have to use the MDA sentence. Here is an example:

$IIMDA,30,I,1.02,B,10.1,C,,C,,,,C,158.69,T,,M,3.89,N,2,M*29

[richarddaneel]

Hi transmitterdan

what are you doing up so late?? Thanks for the reply will try it (in the morning) and see how that goes, best wishes

richard

[conachair]

Originally Posted by transmitterdan

Paul,

I can do it. Sorry, the link I gave was bad. It should be OpenCPN::OpenCPNAll Projects: Tasklist and you have to sign up to be able to add feature requests.

I have a few NMEA streams and the few that I have with baro data have it in the MDA sentence.

I have an online repository of NMEA test streams. If you have any streams that make use of the XDR sentence structure I would love to add them to that repository. We use the files to test OpenCPN so the more variety of data streams we have the better. In fact, any NMEA data files you can share that could be put in the test repository would really help to improve OpenCPN.

Edit: There is an entry in flyspray about this issue. I'll try to follow up and see what can be done.

These are XDR sentances crearted by Openplotter running on a raspberry pi using a BMP180 barometer board.
Hope this helps, it would be great if the dashboard recognized these.

$OSXDR,P,1.0143,B,AIRP,C,18.9,C,AIRT*43

$OSXDR,P,1.0115,B,AIRP,C,19.3,C,AIRT*4B

[richarddaneel]

Hi guys, first of all thanks for all your input, really appreciated. if you have another minute please see if you can add some more. I have tried all three these sentences and they all seem to compile OK in the NMEA debug window but the barometer does not respond, any ideas why????

$OSXDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3

$IIMDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3

$WIXDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3


regards, richard

[conachair]

Originally Posted by richarddaneel

Hi guys, first of all thanks for all your input, really appreciated. if you have another minute please see if you can add some more. I have tried all three these sentences and they all seem to compile OK in the NMEA debug window but the barometer does not respond, any ideas why????

$OSXDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3

$IIMDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3

$WIXDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3


regards, richard

One thing, the checksum *43 at the end looks wrong, there's an online calculator here...
http://www.hhhh.org/wiml/proj/nmeaxor.html

[transmitterdan]

Originally Posted by richarddaneel

Hi guys, first of all thanks for all your input, really appreciated. if you have another minute please see if you can add some more. I have tried all three these sentences and they all seem to compile OK in the NMEA debug window but the barometer does not respond, any ideas why????

$OSXDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3

$IIMDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3

$WIXDR,P,1.0143,B,barometer,C,18.9,C,temperature*4 3


regards, richard

Richard,

OpenCPN only takes barometer data from the MDA sentence. See previous message above. Even if you get the checksum right OpenCPN still will not look for barometer data in any other sentence. Sending it all kinds of other sentences will not make it respond to barometer data.

[conachair]

Originally Posted by transmitterdan

Richard,

OpenCPN only takes barometer data from the MDA sentence. See previous message above. Even if you get the checksum right OpenCPN still will not look for barometer data in any other sentence. Sending it all kinds of other sentences will not make it respond to barometer data.

Which bit of Opencpn looks for the barometer data?

With the sentence below I can't get the dashboard to display barometer data

$IIMDA,30,I,1.02,B,10.1,C,,C,,,,C,158.69,T,,M,3.89 ,N,2,M*29

However almost the same sentence will be recorded by logbook konni as barometer & temperature..
$WIMDA,30,I,1.02,B,10.1,C,,C,,,,C,158.69,T,,M,3.89 ,N,2,M*37

[richarddaneel]

Sorry for the confusion a typo, yes the sentence I used was IIMDA and NOT MDR as indicated, but the barometer still does not recognise IIMDA sentence, any ideas will be appreciated.

thx, richard