NMEA 0183 serial csv data reading

Connectivity External GPS Modules
1

Hi!
Sorry for posting many different questions in one. They are all related to reading an external GPS Module connection.
For the external GPS module connections it appears that there are some GPS and navigational data available under the “ECU specific” menu. My questions below are about how to extend the functionality.

I have successfully connected my external GPS to my windows 10 computer using serial connection (USB) and are able to monitor GPS speed. This works just fine.
I would also like to see status on how many satellites are in view/used.
For the external GPS module it appear to be not possible to add an xml file for data description. Is this only available for the Realdash CAN protocol?

My external GPS sends NMEA _0183 sentences why I presume you have implemented comma-separated serial sentence reading, CSV.
Do you use some kind of nmea-to-can converter or is the “$GPRMC” the only external GPS sentence Realdash reads?

How do I proceed with for an example the satellites-in-view reading where all sentences start with “$GPGSV”?
I tried the Realdash CAN protocol but was not able to get it to work as the CSV stream does not have fixed length data.
Also the identifier is not 4 byte long but 6 (0x24 47 50 52 4D 43).

Do I have to install a NMEA 2000 converter and use the Realdash CAN?

All help is highly appreciated.

2

You are correct, only basic information like speed and location are read from NMEA data stream. I will take a look to read other information from NMEA. I don’t think it makes sense to convert it to CAN as data is already available from the GPS module directly.

3

Thanks for considering this option. I just sent you a pm with further details on the request.

4

The 1.6.9 release has the following new inputs in ‘ECU Specific’ category:

External GPS: Track angle
External GPS: Number of satellites being tracked
External GPS: Horizontal Dillution
External GPS: 3D Fix
External GPS: PDOP
External GPS: HDOP
External GPS: VDOP
External GPS: True track made good
External GPS: Magnetic track made good

for satellites 1-12 in view
External GPS: Satellite #, PRN
External GPS: Satellite #, Elevation (deg)
External GPS: Satellite #, Azimuth (deg)
External GPS: Satellite #, SNR (dB)

These inputs will only appear in list after External GPS connection has been specified. Hope these are enough to get you started.

5

How can I see altitude (elevation) in meters?

6

This input is in ‘Device Inputs->GPS Altitude’

7

For external GPS (usb) to?

8

Yes. External GPS inputs are marked for values that are not available when using device internal GPS.

9

In serial monitor for GPS input I have “$GPGGA,140228.00,1918.74062,N,09907.89891,W,2,10,1.21,2248.3,M,-7.6,M,0000*60”

If I check device inputs :
GPS LATITUDE = 19.3 (I think this is for the convertion factor compared to 1918.74062 on serial read)
GPS LONGITUDE = -99.1 (I think this is for the convertion factor compared to 09907.89891 on serial read)
GPS TIME = 14:02
GPS DATE = 17.11.2020
GPS ALTITUDE = 000000.0 (but in serial value is 2248.3)

Here capture of serial monitor of GPS data

gps_data2.png
gps_data2.png569×678 19.1 KB

10

Ok, I will take a look if there is a problem parsing the altitude from GPGGA.

Edit: I found something that caused the altitude to bounce from 0 to real value and back to 0. Is this the behavior you are seeing in your tests?

11

It’s always 000000.0

12

I will soon publish a beta with a fix, so you can try if what I found fixes this problem.

13

Thanks