This module is part of the original MMBasic library. It is reproduced here with kind permission of Hugh Buckle and Geoff Graham. Be aware it may reference functionality which has changed or is deprecated in the latest versions of MMBasic.¶
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GPS.BAS
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' Demonstration of parsing the NMEA string produced by a GPS module
' Geoff Graham - July 2013
'
' All GPS modules are guaranteed to produce the GPRMC string
' See http://home.mira.net/~gnb/gps/nmea.html for details of the string
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'
max = 20 ' maximum nbr of params
DIM arg$(max) ' used to hold the data fields
OPEN "COM1:4800" AS #1
DO ' loop forever
GetGPSData ' get the next line
IF arg$(0) = "GPRMC" THEN ' GPRMC contains lat/long
IF arg$(2) = "A" THEN ' "A" means locked on to satellites
PRINT "Latitude = "; LEFT$(arg$(3), 2); " "; MID$(arg$(3), 3);
PRINT " "; arg$(4);
PRINT " Longitude = "; LEFT$(arg$(5), 3); " "; MID$(arg$(5), 4);
PRINT " "; arg$(6)
ELSE
PRINT "GPS searching..."
ENDIF
ENDIF
LOOP
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' subroutine to load the GPS data fields into the array arg$()
' returns with the array populated
SUB GetGPSData
DO
DO WHILE INPUT$(1, #1) <> "$" : LOOP ' wait for the start
FOR i = 0 TO max
arg$(i) = "" ' clear ready for data
DO ' loops until a specific exit
x$ = INPUT$(1, #1) ' get the character
IF x$ = "," THEN EXIT ' new data item, increment i
IF x$ = "*" THEN EXIT SUB ' we have all the data so exit
arg$(i) = arg$(i) + x$ ' add to the data
LOOP ' keep going
NEXT i ' increment i
LOOP
END SUB