How do I discern Maidenhead Locator from GPS lat long info.

[tasmod]

Hi Henrik,

Quite a bit to digest there. Good food for thought. Thanks.

I missed the fact that the custom characters for the medium digits was constantly loading in the loop. I've moved that to the beginning now out of the loop, it is loaded at start up.

The BigDigit clock did only load it's characters once then entered it's own loop, so that's taken care of.


The main problem as I see it is that the gps string start occurs at the same time as the 'seconds' rise point. In the gps module the start of the rise of the PPS also triggers the NMEA string output. In other words the seconds epoch occurs for both. I don't know if it's possible to receive the string and trigger the display code at the same time. I was just trying to get to a more accurate time.

The time is very close now anyway allowing for code run timing. I could add a small pause to bring it closer I suppose.

[HenrikOlsson]

Hi Rob,
More thoughts.....
Since, if I'm not mistaken, the time is parsed from the NMEA string using the PPS signal to initiate a display update will update the display with the time information from the last received string which is basically one second "old". I think that the best you can do really is to simply grab and parse the string and then update the display.

If you're receiving the full 82byte NMEA string that will take ~170ms, add the actual display update code to that - you'll be a couple of hundred ms off.

/Henrik.

[tasmod]

Hi Henrik,

I've been doing some more reading regarding the NMEA string from the Rockwell datasheets. (19 pages in one 142 in other !)

I've discovered two choice bits.

(1.) The string is always after the event, so is 1 second late as you said.

(2.) Standard laid down for time this way is up to +/- .9 seconds regardless of (1.) above.

Rockwell do a binary protocol at 9600 baud which is 'message' driven. So you can actually poll for time separately with far more accuracy but it would require a complete code rewrite.


I'm trying to keep code tight in the BigClock sub which only reads the h, m, s, part of string. This is at beginning of the string anyway. I update in reverse to display, s m h.

At the moment I've added 2 seconds before display and with the other code changes, it's as near as I can see visually using the PPS LED. It is almost on the PPS event. That is near enough for me. Checking against MSF radio time signal using Spectrum Lab software, it's very close.
Visually humans can discern a 250ms difference, so as I can hardly see any difference, it should be closer than 250ms diff.
I could load the output into SpecLab to compare both signals I suppose. I may eventually do that anyway as I'm curious to what the code timing is.
I have the frequency lock part spot on, so it would be nice to get the time part as well, but I don't think its possible.

For my sins, in my other life I am an official timekeeper, timing to hundredths of a second. I can see '100ths differences there ok
Amazing really how many times a day I see exactly the same time to the hundreth of a second, two competitors achieve.



Another idea, but I suspect will gain nothing is :-

Read string full time once at start up.
Display

loop:
Then read only seconds.
Increment software clock s m h
update display
loop

String read would be very quick. Approx 20ms.

EDIT:
Just realised that at 20ms I would have read h m s anyway, so pseudo code above is pointless.

[astanapane]

Dear all,

first of all i would like to congrats the work have been done in this post.

I would also like to inform you once again that im not a programmer. So my knowledge at programming is really low.

I try to setup as a hobby a gps and project the info to ulcd that i have many years at my small lab.

Here is the code up to now:

@ ERRORLEVEL -306 ; this command prevents the compiler to give you a notice of
                  ; crossing page boundary - make sure bits are set 

PORTB = 0
input portb.0
; -----[ Variables ]-------

PWRLED      var     PORTb.1   ; this shows that the initialization is finished
LCD         var     PORTb.2   ; to LCD operation
GPS_TX      var     PORTb.0   ; info from GPS 
GPS_RX      var     PORTb.4   ; COMMANDS TO GPS, this feature is not 
Testled     var     PORTb.5   ;ill try to use this when GPS module find signal
pause 2000

' -----[ Variables ]-------------------------------------------------------
'   $GPRMC,090045.000,A,3823.6645,N,02353.3600,E,0.02,195.80,170518,,,A*62
'   $GNGGA,140405.000,3823.6010,N,02353.3054,E,1,9,0.88,0.8,M,35.9,M,,*40

hh          var     byte    'hours
mm          var     byte    'minutes
ss          var     byte    'seconds  
sss         var     word    'milisecs
degrees	    VAR     BYTE    'latitude/longitude degrees
minutes	    VAR     BYTE    'latitude/Longitude minutes
minutesD    VAR	    word    'latitude/LONGITUDE DECIMAL MINUTES
dir         VAR     BYTE    ' direction (latitude: 0 = N, 1 = S / longitude: 0 = E, 1 = W)
degrees2    VAR     BYTE    'latitude/longitude degrees
minutes2    VAR	    BYTE    'latitude/Longitude minutes
minutesD2   VAR	    word    'latitude/LONGITUDE DECIMAL MINUTES
dir2        var     byte    ;direction (latitude: 0 = N, 1 = S / longitude: 0 = E, 1 = W)
SatNo       VAR	    BYTE    'number of satellites connected
knots       var     word    'speed over ground
knots2      var     byte    'speed over ground
course      var     word    'course
course2     var     byte    'course
day         var     byte    'day
month       var     byte    'month
year        var     byte    'year
i           var     word    
GNRMC       var     word
GNGGA       var     WORD
FIX         var     word
Modefix     var     byte
horizon     var     byte
precision   var     byte
meter       var     byte
METERS      var     byte
Meters2     var     byte

' -----------------  [ Initialization ]----------------------
serout2 LCD,32,[$55]      ' uOLED Initialize
pause 2000
serout2 lcd,32,[$56,$01]
pause 1000
serout2 lcd,32,[$45]
pause 500
serout2 lcd,32,[$55]
pause 500
serout2 lcd,32,[$45]
pause 500
serout2 lcd,32,[$73,$00,$03,$11,$ff,$ff," Leonardo Bilalis",$00]
pause 200                       
serout2 lcd,32,[$73,$02,$06,$10,$ff,"     Copyright 2018",$00]
pause 3000
serout2 lcd,32,[$45]
pause 1000
serout2 lcd,32,[$73,$02,$06,$10,$ff,$ff,"      GPS.........",$00]
pause 500
serout2 lcd,32,[$45]
pause 200
HIGH pwrled

'--------------------   [MAIN] ------------------------------

Main: 

;$GPRMC,090045.000,A,3823.6645,N,02353.3600,E,0.02,195.80,170518,,,A*62

serin2 gps_tx,84,[wait("$GNRMC"),_                              ;we wait for $GNRMC
wait(","),dec2 hh,dec2 mm,dec2 ss,wait("."),dec3 sss,_          ;we wait for 090045.000
wait(","),fix,_                                                 ;we wait for A
wait(","),dec2 degrees,dec2 minutes,wait("."),dec4 minutesd,_   ;we wait for 3823.6645
wait(","),dir,_                                                 ;we wait for N 
wait(","),dec3 degrees2,dec2 minutes2,wait("."),dec4 minutesd2,_;we wait for 02353.3600
wait(","),dir2,_                                                ;we wait for E
wait(","),dec knots,wait("."),dec2 knots2,_                     ;we wait for 0.02
wait(","),dec3 course,wait("."),_                               ;we wait for 195.80
wait(","),dec2 day,dec2 month,dec2 year]                        ;we wait for 170518

pause 100

;$GNGGA,140405.000,3823.6010,N,02353.3054,E,1,9,0.88,0.8,M,35.9,M,,*40

serin2 gps_tx,84,[wait("$GNGGA"),_
wait(","),dec2 hh,dec2 mm,dec2 ss,wait("."),dec3 sss,_ 
wait(","),dec2 degrees,dec2 minutes,wait("."),dec4 minutesd,_ 
wait(","),dir,_
wait(","),dec3 degrees2,dec2 minutes2,wait("."),dec4 minutesd2,_
wait(","),dir2,_
wait(","),modefix,_
wait(","),dec2 satno,_
wait(","),dec3 horizon,dec precision,_
wait(","),meter,dec2 METERS,dec Meters2]

pause 100

serout2 lcd,32,[$73,$03,$00,$00,$ff,$ff,"Protocol:",dec5 GNRMC,$00] ; THIS IS NOT WORKING
pause 200
serout2 lcd,32,[$73,$00,$02,$00,$ff,$ff,"Date:",dec2 day,dec2 month,dec2 year,$00] ; THIS IS NOT WORKING
pause 200
serout2 lcd,32,[$73,$00,$04,$00,$ff,$ff,"TIME: ",dec2 hh+3," :",dec2 mm," :",dec2 ss,$00]
pause 200
serout2 lcd,32,[$73,$00,$06,$00,$ff,$ff,"Satellites:",dec2 satno," ","Fixed:",fix,$00]
pause 200
serout2 lcd,32,[$73,$00,$08,$00,$ff,$ff,"Lat : ",dec2 degrees,dec2 minutes,".",dec4 minutesd," ",dir,$00]
pause 200
serout2 lcd,32,[$73,$00,$0A,$00,$ff,$ff,"Lon : ",dec3 degrees2,dec2 minutes2,".",dec4 minutesd2," ",dir2,$00]
pause 200
serout2 lcd,32,[$73,$00,$0C,$00,$ff,$ff,"GND SPEED : ",dec knots*1852/1000,".",dec2 knots2,$00]
pause 200
serout2 lcd,32,[$73,$00,$0E,$00,$ff,$ff,"Meters : ",dec2 METERS,dec Meters2,$00] ; THIS IS NOT WORKING

pause 5000
serout2 lcd,32,[$45]
pause 100
goto main

if fix = "V" then notfix

notfix: 
serout2 lcd,32,[$73,$00,$03,$11,$ff,$ff,"   Waiting for GPS",$00]
pause 100
serout2 lcd,32,[$73,$02,$06,$10,$ff,"     Copyright 2018",$00]
pause 1000
serout2 lcd,32,[$45]
pause 200
goto main

'-------------------- [ CLEAR ] -----------------------------
Clearlcd:
serout2 lcd,32,[$45]
pause 500
RETURN

What i would like to do is to display:

Protocol : GNRMC

DATE :
TIME :
Satellites:
LAT :
LON :
GND SPEED:
METERS:

I have the following problem.

1. Cannot display the DATE. Something is wrong at my code and there is not proper display of the date.
2. I have put a loop for display all the factors, because i need to clear the LCD every time something is change. So please could you help me understand how could i manage to display the factors and only change on the fly the ones really going like Time, LAT, LON, GND SPEED, SATs etc.
3. The Protocol command is not working
4. The speed is not working properly, i think i need to do better the conversion
5. The meters are not displaying, there is a wrong value in there.
6. I need to convert the measurements from the NMEA message LAT and LON to google numbers.

Please check what i have done till now in order for me to understand what it is needed.

[astanapane]

I have updated a little bit the code so when there is a no data at portb.0 to have a notice.

but still i need to fix the following. Is there any advise?

1. Cannot display the DATE. Something is wrong at my code and there is not proper display of the date.
2. I have put a loop for display all the factors, because i need to clear the LCD every time something is change. So please could you help me understand how could i manage to display the factors and only change on the fly the ones really going like Time, LAT, LON, GND SPEED, SATs etc.
3. The Protocol command is not working
4. The speed is not working properly, i think i need to do better the conversion
5. The meters are not displaying, there is a wrong value in there.
6. I need to convert the measurements from the NMEA message LAT and LON to google numbers.

'*  Author  : LEONARDO BILALIS                                  *
'*  Notice  : Copyright (c) 2018 [LEONARDOS BILALIS]            *
'*          : All Rights Reserved                               *
'*  Date    : 12/5/2018                                         *
'*  Version : 1.0                                               *
'*  Notes   : This is an GPS                with ulcd           * 
'*          :                                                   *
'****************************************************************

@ ERRORLEVEL -306 ; this command prevents the compiler to give you a notice of
                  ; crossing page boundary - make sure bits are set 

;& __config _HS_OSC & _WDT_ON & _LVP_OFF & _CP_OFF

Include "MODEDEFS.BAS"
DEFINE OSC 8    
OSCCON=%01111000     '8 Mhz
CMCON = 7            'turn comparators off
ANSEL = 0            'All digital
PORTB = 0            'make low all ports at B range
input portb.0        'make input portb.0


'----------------------------------------------------------------------------/
'                              [ PIC Variables ]                            /  
'--------------------------------------------------------------------------/

PWRLED      var     PORTb.1   ; this shows that the initialization is finished
LCD         var     PORTb.2   ; to LCD operation
GPS_TX      var     PORTb.0   ; info from GPS 
GPS_RX      var     PORTb.4   ; COMMANDS TO GPS
Testled     var     PORTb.5 
dots        var     byte
dots=8
countremain var     byte      ; we use a countremain to check the incoming from portb.0  
pause 1000

' --------------------[ GPS Variables for NMEA sentenses ]---------------------/
'                                                                             /
'   $GPRMC,090045.000,A,3823.6645,N,02353.3600,E,0.02,195.80,170518,,,A*62   /
'   $GNGGA,140405.000,3823.6010,N,02353.3054,E,1,9,0.88,0.8,M,35.9,M,,*40   /
'                                                                          /
'-------------------------------------------------------------------------/

hh          var     byte    'hours
mm          var     byte    'minutes
ss          var     byte    'seconds  
sss         var     word    'milisecs
degrees		VAR     BYTE	'latitude/longitude degrees
minutes		VAR		BYTE	'latitude/Longitude minutes
minutesD	VAR		word	'latitude/LONGITUDE DECIMAL MINUTES
dir       	VAR     BYTE   	' direction (latitude: 0 = N, 1 = S / longitude: 0 = E, 1 = W)
degrees2	VAR     BYTE	'latitude/longitude degrees
minutes2	VAR		BYTE	'latitude/Longitude minutes
minutesD2	VAR		word	'latitude/LONGITUDE DECIMAL MINUTES
dir2        var     byte    ;direction (latitude: 0 = N, 1 = S / longitude: 0 = E, 1 = W)
SatNo   	VAR		BYTE	'number of satellites connected
knots       var     word    'speed over ground
knots2      var     byte    'speed over ground
course      var     word    'course
course2     var     byte    'course
day         var     byte    'day
month       var     byte    'month
year        var     byte    'year
i           var     word    
GNRMC       var     word    'protocol
GNGGA       var     WORD    'protocol
FIX         var     word    'fix sat V/A
Modefix     var     byte    'mode fix 1 or 2 or 3 depens
horizon     var     byte
precision   var     byte
meter       var     byte
METERS      var     byte
Meters2     var     byte

' -------------------------------------------------------------------------/  
'                          [ LCD Initialization ]                         /
'------------------------------------------------------------------------/

serout2 LCD,32,[$55]      ' uOLED Initialize
pause 2000
serout2 lcd,32,[$56,$01]
pause 1000
serout2 lcd,32,[$45]      ' clear the lcd
pause 500
serout2 lcd,32,[$55]
pause 500
serout2 lcd,32,[$45]      ' clesr the lcd
pause 500
serout2 lcd,32,[$73,$00,$03,$11,$ff,$ff," Leonardo Bilalis",$00]
pause 200                       
serout2 lcd,32,[$73,$02,$06,$10,$ff,"     Copyright 2018",$00]
pause 3000
serout2 lcd,32,[$45]
pause 1000
serout2 lcd,32,[$73,$02,$06,$10,$ff,$ff,"      GPS.........",$00]
pause 500
serout2 lcd,32,[$45]
pause 200

'----------------------------------------------------------------------/
'     [ After the lcd initialization we power the Led at PIC ]        /
'--------------------------------------------------------------------/

HIGH pwrled

'-------------------------------------------------------------------/
'                         [MAIN Program]                           /
'-----------------------------------------------------------------/

Main: 
;gosub clearlcd

serin2 gps_tx,84,[countremain]      ; we check what is coming from the port
if countremain = 0 then lostcable   ; if nothing is coming the we check the cable

;gosub clearlcd
'-------------------------------------------------------------------------------/
'                                                                              /
'                    [ Example NMEA Sentense of GNRMC ]                       /
' [$GNRMC,090045.000,A,3823.6645,N,02353.3600,E,0.02,195.80,170518,,,A*62]   /
'                                                                           /
'--------------------------------------------------------------------------/

serin2 gps_tx,84,[wait("$GNRMC"),_                              ;we wait for $GNRMC
wait(","),dec2 hh,dec2 mm,dec2 ss,wait("."),dec3 sss,_          ;we wait for 090045.000
wait(","),fix,_                                                 ;we wait for A
wait(","),dec2 degrees,dec2 minutes,wait("."),dec4 minutesd,_   ;we wait for 3823.6645
wait(","),dir,_                                                 ;we wait for N 
wait(","),dec3 degrees2,dec2 minutes2,wait("."),dec4 minutesd2,_;we wait for 02353.3600
wait(","),dir2,_                                                ;we wait for E
wait(","),dec knots,wait("."),dec2 knots2,_                     ;we wait for 0.02
wait(","),dec3 course,wait("."),_                               ;we wait for 195.80
wait(","),dec2 day,dec2 month,dec2 year]                        ;we wait for 170518

pause 100

'------------------------------------------------------------------------------/
'                                                                             /
'                     [ Example NMEA Sentense of GNGGA ]                     /
' [$GNGGA,140405.000,3823.6010,N,02353.3054,E,1,9,0.88,0.8,M,35.9,M,,*40    /           
'                                                                          /
'-------------------------------------------------------------------------/

serin2 gps_tx,84,[wait("$GNGGA"),_
wait(","),dec2 hh,dec2 mm,dec2 ss,wait("."),dec3 sss,_ 
wait(","),dec2 degrees,dec2 minutes,wait("."),dec4 minutesd,_ 
wait(","),dir,_
wait(","),dec3 degrees2,dec2 minutes2,wait("."),dec4 minutesd2,_
wait(","),dir2,_
wait(","),modefix,_
wait(","),dec2 satno,_
wait(","),dec3 horizon,dec precision,_
wait(","),meter,dec2 METERS,dec Meters2]

pause 100


'---------------------------------------------------------------------------------/
' Here if the GPS module havent been fixed to any satellite will jump to notfix  /
'-------------------------------------------------------------------------------/

if fix = "V" then notfix                                                        
pause 100

'-----------------------------------------------------------------------------/
'                           [ Return from notfix ]                           /
'                   [ We clear any character on the display ]               /
'--------------------------------------------------------------------------/

gosub clearlcd
;serout2 lcd,32,[$45]
;pause 500


'--------------------------------------------------------------------------/
' here is where the code dispays the stored info from the NMEA sentenses  /
'------------------------------------------------------------------------/

serout2 lcd,32,[$73,$03,$00,$00,$ff,$ff,"Protocol:",dec5 GNRMC,$00]
pause 100
serout2 lcd,32,[$73,$00,$02,$00,$ff,$ff,"Date:",dec2 day,dec2 month,dec2 year,$00]
pause 100
serout2 lcd,32,[$73,$00,$04,$00,$ff,$ff,"TIME: ",dec2 hh+3," :",dec2 mm," :",dec2 ss,$00]
pause 100
serout2 lcd,32,[$73,$00,$06,$00,$ff,$ff,"Satellites:",dec2 satno," ","Fixed:",fix,$00]
pause 100
serout2 lcd,32,[$73,$00,$08,$00,$ff,$ff,"Lat : ",dec2 degrees,dec2 minutes,".",dec4 minutesd," ",dir,$00]
pause 100
serout2 lcd,32,[$73,$00,$0A,$00,$ff,$ff,"Lon : ",dec3 degrees2,dec2 minutes2,".",dec4 minutesd2," ",dir2,$00]
pause 100
;serout2 lcd,32,[$73,$00,$0C,$00,$ff,$ff,"GND SPEED : ",(dec knots,".",dec2 knots2)*/1.852,$00]
;pause 200
serout2 lcd,32,[$73,$00,$0E,$00,$ff,$ff,"Meters : ",dec2 METERS,dec Meters2,$00]
pause 3000
serout2 lcd,32,[$45]  ' clears the LCD 
pause 100

        goto main

'-----------------------------------------------------------------------------/
'                              [ SUB ROUTINES ]                              /
'---------------------------------------------------------------------------/

notfix:     ' Still looking for fixed signal
 
serout2 lcd,32,[$73,$00,$03,$11,$ff,$ff,"   Waiting for GPS",$00]
pause 100
serout2 lcd,32,[$73,$03,$06,$10,$ff," Time:",dec2 hh+3," :",dec2 mm," :",dec2 ss,$00]
pause 1000
serout2 lcd,32,[$73,$03,$08,$10,$ff,rep "."\dots,$00]
pause 200
serout2 lcd,32,[$45]  ' clears the LCD 
pause 100

goto main       'returns to main

lostcable:
serout2 lcd,32,[$73,$00,$03,$11,$ff,$ff,"   Connection lost",$00]
pause 100
serout2 lcd,32,[$73,$01,$06,$10,$ff,"   Please check cable",$00]
pause 2000
serout2 lcd,32,[$45]  ' clears the LCD 
pause 100

goto main

'---------------------------------------------------------------------------/
'                              [ CLEAR LCD ]                               /
'-------------------------------------------------------------------------/

Clearlcd:
serout2 lcd,32,[$45]
pause 100
RETURN

[richard]

first off , what has your post got to do with maidenhead ? why not start a new relevant post instead of confusing this one

secondly posting figures as pictures makes life difficult for anyone inclined to assist


in you google numbers query (which is really deg ,min, sec conversion to decimal degrees )

how did you get 38 + 2/60 + 3.49/3600 = 38.034297

my calculator says 38.0343027 ps (in 32 bit float result is 38.0343018, with 64 bit float 38.0343028)done on pic24f using xc16

you will have fun trying to get math accurate to 10 significant digits on that chip [even 32 bit floats struggle]
your best bet is nbit math

the decimal portion can be :-
mins *1000000/6 + sec *1000/36

parsing the nmea sentences is well covered but you may be interested in this

http://support.melabs.com/forum/picb...strtok-usercmd

a strtok function for pbp

parsing strings with spaghetti code will always by a shortcut to madness

[astanapane]

Hi richard,

1) i did post in here because i was planning to do that conversion as well on next step. But i cant simply display the date, so my knowledge wont be able to do any further

2) pictures i believe always help.

3) you are right on the calculation 38.0343027. I did something wrong in there.

4) if Parsing NMEA is ok then why Date is not displaying right? I will check once again what i have done on the code.

5) i will check the link and the strtok. But i find easier the way i did it because i understand it.

as i said im not a programmer. This code might be simple for you, but is too much for me. I try to do things stwp by step on this code. There are lots of bugs and mistakes which at the moment cant solve.

i found a small mistake on the first parsing code. i have forgot a sentence which may cause the problem displaying date.

Will keep you update.