JBperf GPS - CAN format info?

[MWPau]

Hi all,

The MS3 supports requesting GPS data via CAN using the "JBperf GPS" option.
Is there any info anywhere on the data format / locations?

I want to supply GPS data to my MS3 from my DIY dash display.

Thanks.

[racingmini_mtl]

The is the extract from the IOx ini file related to the GPS data read by the MS3:

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   gps_latdeg       = scalar, S08,  128, "", 1,0
   gps_latmin       = scalar, U08,  129, "", 1,0
   gps_latmmin      = scalar, U16,  130, "", 1,0
   gps_londeg       = scalar, U08,  132, "", 1,0
   gps_lonmin       = scalar, U08,  133, "", 1,0
   gps_lonmmin      = scalar, U16,  134, "", 1,0
   gps_outstatus    = scalar, U08,  136, "", 1,0
   gps_altk         = scalar, S08,  137, "", 1,0
   gps_altm         = scalar, S16,  138, "", 0.1,0
   gps_speedms      = scalar, U16,  140, "", 0.1,0
   gps_course       = scalar, U16,  142, "", 0.1,0

The offset you see is the one used by the IOx so you can change that but the relative position and the scaling have to be respected for the MS3 to be able to read the data correctly.

Jean

[MWPau]

Ah ha!
I didnt think to look there, thanks.

Now to work out what gps_outstatus represents.

[racingmini_mtl]

This:

Code: Select all

  unsigned char gps_outstatus;// bit 0 : 0=E, 1=W; bit 1 : 0=invalid data, 1=valid data; bits 2, 3 TBD; bits 4-7 : frame counter

Since the longitude can't fit in a signed 8-bit variable (0-180 degrees east or west), there is a bit in the status to specify if it's east or west. The second bit specifies if the GPS has locked onto satellites and is generating valid data. The upper nibble (4 bits) is for a counter that tells the MS3 if the data it read has been updated or if it's just the same data or if a frame has been missed. It goes from 0 to 15 and rolls back to 0.

Jean

[MWPau]

Perfect, thanks again Jean!

[xrattiracer]

thats good info, i will have to update my code since i only knew about the E/W bit. seems to work just fine without everything else though, checked the post i just made in the expansion boards section for a screenshot

[MWPau]

Im having some trouble with the format of the variables

What does mmin refer to? As in gps_latmmin?
It doesn't appear to be seconds as TS then displays the wrong value.

I assumed altk and altm would be 'altitude kilometers' and 'altitude meters', but it doesnt seem be to correct.
Course is odd too.

[racingmini_mtl]

mmin refers to milli-minutes (thousandths of minutes) since the the NMEA senstences from the GPS gives the data in fractions of minutes. The altitude in meters is (altk X 1000) + altm. The course is in tenths of degrees with respect to the true north.

These are all data taken directly from the GPRMC NMEA sentence except that the speed is converted from knots to m/s.

Jean