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Author Topic: NMEA GPS Pic Basic Routine?  (Read 7848 times)
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iampic
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« on: December 03, 2007, 12:28:43 12:28 »

Does anyone know where I can find (if exist) GPS NMEA routines to talk with GPS serial modules?
Thanks, Iampic
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jorge7458
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« Reply #1 on: December 03, 2007, 01:21:56 13:21 »

Hello:   
Does the protocol give a series of data in ASCII. Exactly that what you want is?
Jorge

Posted on: December 03, 2007, 01:16:14 13:16 - Automerged

Hi:
Check this:
http://www.protongeeks.com/index.php?option=com_content&task=view&id=80&Itemid=27
Jorge
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margo
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« Reply #2 on: December 03, 2007, 03:38:07 15:38 »

proteus gps receiver see rar file attached

here is a basic nema gps reader displayed on a 40x2 lcd, source included, written for Picbasic pro,

(sw1 is used to adjust from UTC(GMT) time to BST)

connect a gps receiver to the com2 port and it will display the info on the lcd, select properties of the virtual com port to change to com1 etc,

led is green for valid data , red for invalid (this routine needs tidying)

***UPDATE 25/3/10 im informed that the gps time will be out by about 15 seconds, this is because gps time doenst have leap seconds subtracted, and its slightly fast, can anyone confirm this?***
« Last Edit: March 26, 2010, 12:04:26 00:04 by margo » Logged
iampic
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« Reply #3 on: December 10, 2007, 01:36:03 13:36 »

I know that is just an ascii stream, I need routines to parse and collect data, make averages, calculus etc. without write from scratch.
Thanks, Iampic
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Alienbeing
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« Reply #4 on: December 17, 2007, 03:43:04 03:43 »

I did alot of research on this for the same kind of project. My code is all written in assembly. There is not really much example code (in Basic) on the internet that you will find. Matter of fact it was difficult to locate any good useable code at all. My assembly code does basically the same. It will retrieve NEMA ascii data from an Juipter GPS module into a PIC 16F877 UART, then parse Date, Time (UTC), Lat, Long, and altitude.
Then it is displayed on a 4x20 LCD display. Works great in Proteus, and compiled for PIC it works great too.
What I need to do next is convert UTC time to local time. I will share my code here later when I am satisfied that it is without bugs(don't think there are any right now), and is optimized for speed. I do notice that displayed seconds is not displaying at exactly the right time. This is due to the fact as other strings are being parsed it delays the display of seconds in accurate timeing. Not a big deal anyway as it still keeps very accurate time. Parsing the Altitude is what is causing the delay. Thinking of just getting rid of that. I really don't need Lat and Long either as this is a stationary piece of equipment (GPS locked 10mhz frequency standard). Was not meant to go mobile. But I would like to keep the code the way it is in case I develop a mobile embedded application. I have about 30 of these Juipter GPS's and thinking of developing more projects using them. Maybe for GPS tracking.
Once you get the concept of how to parse the data then parsing additional data is not that hard to do. I did have some help with my code from a member here ( LCD Busy Flag coding) and he will get credit for it in the final code when the project is completed. Lots of good people here to help but you can't expect someone to write all the code for you. I've never written assembly code before and had to learn a great deal on my own.

Alienbeing
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picavr
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« Reply #5 on: December 27, 2007, 01:11:58 13:11 »

you can see:
hxxp://www.picbasic.org/forum/showthread.php?t=211
hxxp://www.electrotech.net.au/ea_downloads.php?category=utilities
hxxp://www.gpsinformation.org/dale/nmea.htm
there is a program in basic with 18f :
hxxp://snipplr.com/view/2191/interfacing-picmicro-18f-to-rtc-and-gps/
another:
hxxp://www.expandedspectrumsystems.com/sync2.bas
good lucky
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Cynetron
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« Reply #6 on: February 02, 2008, 12:24:02 00:24 »

Code:
' ==============================================================================
'
'   File...... AEROGPS3.BSP
'   Purpose...
'   Author.... Parallax
'   E-mail.... stamptech@parallaxinc.com
'   Started... 16 JUL 2001
'   Updated... 08 MAY 2002
'
'   { $STAMP BS2p }
'
' ==============================================================================


' ------------------------------------------------------------------------------
' Program Description
' ------------------------------------------------------------------------------
'
' This program captures and records GPS data from consumer receiver
' (i.e. Garmin eTrex or equivalent) using standard NMEA output.
'
' Standard NMEA 0183 string:
'
' $GPRMC,POS_UTC,POS_STAT,LAT,LAT_D,LON,LON_D,SPD,HDG,DATE,MAG_VAR,MAG_REF,*CC
'
'   POS_UTC  - UTC of position. Hours, minutes and seconds. (hhmmss)
'   POS_STAT - Position status. (A = Data valid, V = Data invalid)
'   LAT      - Latitude (ddmm.ffff)
'   LAT_D    - Latitude direction. (N = North, S = South)
'   LON      - Longitude (dddmm.ffff)
'   LON_D    - Longitude direction (E = East, W = West)
'   SPD      - Speed over ground. (knots) (0.0 - 999.9)
'   HDG      - Heading/track made good (degrees True) (x.x)
'   DATE     - Date (ddmmyy)
'   MAG_VAR  - Magnetic variation (degrees) (x.x)
'   MAG_REF  - Magnetic variation (E = East, W = West)
'   *CC      - Checksum
'
' Custom Garmin string:
'
' $PGRMZ,ALT,F,X*CC
'
'   ALT,F    - Altitude in feet
'   X        - Position fix dimensions (2 = user, 3 = GPS)
'   *CC      - Checksum


' ------------------------------------------------------------------------------
' Revision History
' ------------------------------------------------------------------------------
' Set Debug pin port
DEFINE DEBUG_REG PORTB

' Set Debug pin bit
DEFINE DEBUG_BIT 0

' Set Debug baud rate
DEFINE DEBUG_BAUD 9600

' Set Debug mode: 0 = true, 1 = inverted
DEFINE DEBUG_MODE 1


' ------------------------------------------------------------------------------
' I/O Definitions
' ------------------------------------------------------------------------------

GPSpin            CON     0
Buttons VAR InD ' clear & start inputs (12, 13)
MemLED CON 14 ' on (RED) if records in log
RunLED CON 15 ' on (GREEN) when logging

DoMenu          VAR    IN7                      ' 0 = test using DEBUG report
                                                ' 1 = log data

RxD              CON     16                      ' DEBUG terminal input


' ------------------------------------------------------------------------------
' Constants
' ------------------------------------------------------------------------------

T9600           CON     240                     ' 9600-8-N-1 (matches DEBUG)
N4800           CON     16884                   ' 4800-8-N-1 (for GPS output)

MoveTo          CON     2                       ' DEBUG positioning command
LF              CON     10                      ' linefeed
ClrRt           CON     11                      ' clear line right of cursor

EESlot          CON     1                       ' data starts in this slot
MaxAddr         CON     8 - EESlot * 2048 - 1   ' last available address
FirstAddr       CON     2                       ' make room for readings

Comma           CON     ","                     ' report field delimiter

RecSize         CON     11                      ' 11 bytes for each record

On CON 1 ' LEDs are active high
Off CON 0

Yes CON 1
No CON 0


' ------------------------------------------------------------------------------
' Variables
' ------------------------------------------------------------------------------

records         VAR     Word                    ' stored records
response        VAR     Byte                    ' terminal response character

idx             VAR     response                ' index into SPRAM

btns VAR Nib ' returns button input
btnClear VAR btns.Bit0 ' pin 12
btnRun VAR btns.Bit1 ' pin 13

flags           VAR     Byte                    ' valid, N/S, E/W
valid           VAR     flags.Bit7              ' 0 = valid

latDeg          VAR     Byte                    ' latitude degrees
latFrac         VAR     Word                    ' fractional degrees
latFrLo         VAR     latFrac.LowByte
latFrHi         VAR     latFrac.HighByte
latNS           VAR     flags.Bit0              ' 0 = N

lonDeg          VAR     Byte                    ' longitude degrees
lonFrac         VAR     Word                    ' fractional degrees
lonFrLo         VAR     lonFrac.LowByte
lonFrHi         VAR     lonFrac.HighByte
lonEW           VAR     flags.Bit1              ' 0 = E

altitude        VAR     Word                    ' above sea-level
altLo           VAR     altitude.LowByte
altHi           VAR     altitude.HighByte

speed           VAR     Word                    ' mph
spdLo           VAR     speed.LowByte
spdHi           VAR     speed.HighByte

char            VAR     Byte                    ' byte pulled from SPRAM
workVal         VAR     Word                    ' for numeric conversions

field           VAR     Nib                     ' field #
fldWidth        VAR     field                   ' width of field

eeAddr          VAR     Word                    ' flat EE address
eeData          VAR     Byte

recNum          VAR     workVal                 ' loop counter for reports


' ------------------------------------------------------------------------------
' EEPROM Data
' ------------------------------------------------------------------------------


' ------------------------------------------------------------------------------
' Initialization
' ------------------------------------------------------------------------------

Initialize:
  STORE EESlot                                  ' point to data slot
  READ 0, records.LowByte                       ' retrieve records from EEPROM
  READ 1, records.HighByte
 
  Outs.LowBit(MemLED) = Off ' assume no records
  OUTPUT MemLED ' enable mem LED
  Outs.LowBit(RunLED) = Off
  OUTPUT RunLED ' enable run LED

  PAUSE 250                                     ' allow DEBUG window to open
  DEBUG CLS

  BRANCH DoMenu, [Show_Menu, Check_Input]


Show_Menu:
  DEBUG "AeroGPS - Version 3 (", DEC records, " records)", CR, CR
  DEBUG "[1] View live GPS data", CR
  DEBUG "[2] Dump datalog to PC (Detail Format)", CR, CR, "--> "

  SERIN  RxD, T9600, [response]
  DEBUG CLS

  IF (response < "1") OR (response > "2") THEN Show_Menu
  BRANCH (response - "1"), [Main, Dump_Raw]
  GOTO Show_Menu 


Check_Input:
  LOW RunLED
  Outs.LowBit(MemLED) = (records / records)
  GOSUB Get_Buttons

Check_Clear:
  IF (btnClear = No) THEN Check_Run
  records = 0
  DEBUG CLS, "Records cleared."
  GOTO Check_Input

Check_Run:
  IF (btnRun = No) THEN Check_Input
  LOW MemLED
  HIGH RunLED
  DEBUG CLS, "Running"
  PAUSE 1000 ' give time for button release


' ------------------------------------------------------------------------------
' Program Code
' ------------------------------------------------------------------------------

Main:
  GOSUB Get_Buttons
  IF (btnRun = No) THEN Acquire_Signal ' stop if Run pressed


Wait_For_Run_Release:
  LOW RunLED
  Outs.LowBit(MemLED) = (records / records) 
  GOSUB Get_Buttons
  IF (btnRun = Yes) THEN Wait_For_Run_Release ' for user to release button
  GOTO Check_Input


Acquire_Signal:
  ' capture GPS data, parse $GPMRC string

  SERIN GPSpin, N4800, 3000, No_GPS_Data, [WAIT("GPRMC,"), SPSTR 65]
  GOSUB Parse_GPS

  ' pull altitude from Garmin $PGRMZ string

  SERIN GPSpin, N4800, 1500, Main, [WAIT("PGRMZ,"), DEC altitude]

  BRANCH DoMenu, [Show_GPS_Signal]             ' show signal if in test mode

Log_GPS_Data:
  BRANCH ~valid, [Main]                         ' don't log bad signal

  records = records + 1
  eeAddr = (records - 1) * RecSize + FirstAddr
  IF ((eeAddr + RecSize - 1) > MaxAddr) THEN EE_Full

  eeAddr = eeAddr + 0 : eeData = flags   : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = latDeg  : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = latFrLo : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = latFrHi : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = lonDeg  : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = lonFrLo : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = lonFrHi : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = altLo   : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = altHi   : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = spdLo   : GOSUB Write_Big_EE
  eeAddr = eeAddr + 1 : eeData = spdHi   : GOSUB Write_Big_EE

  STORE EESlot                                  ' save records in data slow
  WRITE 0, records.LowByte
  WRITE 1, records.HighByte

  DEBUG CLS, "Log: ", DEC records, CR
  GOTO  Main

Show_GPS_Signal:
  DEBUG Home, "GPS Signal Test Mode", ClrRt, CR, CR

  BRANCH ~valid, [Bad_Signal]

  DEBUG "  Latitude:  ", DEC2 latDeg, ".", DEC4 latFrac
  DEBUG " ", "N" + (latNS * 5), CR
  DEBUG " Longitude: ",  DEC3 lonDeg, ".", DEC4 lonFrac
  DEBUG " ", "E" + (lonEW * 18), CR
  DEBUG "  Altitude: ",  DEC altitude, " ft.", ClrRt, CR
  DEBUG "     Speed: ",  DEC (speed / 10), "."
  DEBUG DEC1 (speed // 10), " mph", ClrRt
  GOTO Main

Bad_Signal:
  DEBUG "-- Invalid Signal", ClrRt, CR, ClrRt, CR, ClrRt, CR, ClrRt, CR
  GOTO Main

' *******************************
' Stamp EE is full -- handle here
' *******************************

EE_Full:
  LOW RunLED
  HIGH MemLED
  PAUSE 500
  LOW MemLED
  PAUSE 500
  GOTO EE_Full


  ' do something to indicate
  ' HIGH MemFull                                ' turn on LED

  END


' ------------------------------------------------------------------------------
' Subroutines
' ------------------------------------------------------------------------------

Get_Buttons:
  btns = %0011 ' assume buttons pressed
  FOR workVal = 1 TO 5
    btns = btns & ~Buttons ' invert input for active low
    PAUSE 10
  NEXT
  RETURN


No_GPS_Data:
  DEBUG CLS, "Error: No GPS detected"
  PAUSE 1000
  GOTO Initialize                               ' try again


Clear_Log:
  records = 0                                   ' clear records counter
  STORE EESlot                                  ' point to first data slot
  WRITE 0, 0                                    ' clear EE log of count
  WRITE 1, 0
  RETURN


' **************************
' Parse data from GPS stream
' **************************

Parse_GPS:
  idx = 9 : fldWidth = 2                        ' latitude degrees
  GOSUB String_To_Value
  latDeg = workVal

  idx = 11 : fldWidth = 2                       ' latitude minutes
  GOSUB String_To_Value
  latFrac = workVal * 1000 / 6                  ' convert to fractional degrees

  idx = 14 : fldWidth = 4                       ' latitude fractional minutes
  GOSUB String_To_Value
  latFrac = latFrac + (workVal * 36 / 100)      ' add to fractional degrees

  idx = 21 : fldWidth = 3                       ' longitude degrees
  GOSUB String_To_Value
  lonDeg = workVal

  idx = 24 : fldWidth = 2                       ' longitude minutes
  GOSUB String_To_Value
  lonFrac = workVal * 1000 / 6                  ' convert to fractional degrees

  idx = 27 : fldWidth = 4                       ' longitude fractional minutes
  GOSUB String_To_Value
  lonFrac = lonFrac + (workVal * 36 / 100)      ' add to fractional degrees

  ' get character info -- convert to bits

Check_Valid:
  GET 7, char
  valid = char.Bit1                             ' 0 = Valid, 1 = Warning

Get_NS:
  GET 19, char
  latNS = char.Bit0                             ' 0 = North, 1 = South

Get_EW:
  GET 32, char
  lonEW = char.Bit1                             ' 0 = East, 1 = West

Get_Speed:
  idx = 34
  GOSUB Mixed_To_Tenths                         ' convert "xxx.x" to number
  ' speed = workVal                             ' speed in knots (tenths)
  speed = workVal + (workVal ** $2699)          ' x 1.1507771555 for mph

' *********************************************
' Convert string data (nnnn) to numeric value
' -- idx      - location of first digit in data
' -- fldWidth - width of data field (1 to 5)
' -- workVal  - returns numeric value of field
' *********************************************

String_To_Value:
  workVal = 0
  IF (fldWidth = 0) OR (fldWidth > 5) THEN String_To_Value_Done

Get_Field_Digit:
  GET idx, char                                 ' get digit from field
  workVal = workVal + (char - "0")              ' convert, add into value
  fldWidth = fldWidth - 1                       ' decrement field width
  IF (fldWidth = 0) THEN String_To_Value_Done
  workVal = workVal * 10                        ' shift result digits left
  idx = idx + 1                                 ' point to next digit
  GOTO Get_Field_Digit

String_To_Value_Done:
  RETURN

' *****************************************************
' Convert string data (nnn.n) to numeric value (tenths)
' -- idx     - location of first digit in data
' -- workVal - returns numeric value of field
' *****************************************************

Mixed_To_Tenths:
  workVal = 0

Get_Mixed_Digit:
  GET idx, char                                 ' read digit from speed field
  IF (char = ".") THEN Get_Mixed_Last           ' skip decimal point
  workVal = (workVal + (char - "0")) * 10       ' add digit, move data left
  idx = idx + 1                                 ' point to next digit
  GOTO Get_Mixed_Digit

Get_Mixed_Last:
  GET (idx + 1), char                           ' point to tenths digit
  workVal = workVal + (char - "0")              ' workVal is in tenths
  RETURN

' ************************************************************
' Find field location after variable-length data (i.e., speed)
' -- field - field number
' -- idx   - returns position of first digit in field
' ************************************************************
'
' Move_To_Field:
'   idx = 0
'   IF (field = 0) THEN Move_To_Field_Done        ' if zero, we're there
'
' Get_Char:
'   GET idx, char                                 ' get char from SPRAM
'   IF (char = Comma) THEN Found_Comma            ' is it a comma?
'   idx = idx + 1                                 ' no, move to next char
'   GOTO Get_Char
'
' Found_Comma:
'   field = field - 1                             ' was comma, dec field coutner
'   idx = idx + 1                                 ' point to next char
'   IF (field = 0) THEN Move_To_Field_Done        ' if field = 0, we're there
'   GOTO Get_Char
'
' Move_To_Field_Done:
'   RETURN

' ******************************
' Write data to "flat" EE memory
' ******************************

Write_Big_EE:
  IF (eeAddr > MaxAddr) THEN No_Write           ' check for bad eeAddr
  STORE (eeAddr / 2048) + EESlot                ' point to EE slot
  WRITE (eeAddr // 2048), eeData

No_Write:
  RETURN


' ------------------------------------------------------------------------------
' Reports
' ------------------------------------------------------------------------------

Dump_Raw:
  ' dump for detailed analysis
  ' -- <record>,<latitude>,<N/S>,<longitude>,<E/W>,<altitude>,<speed>
  ' -- <xxx>,<xx.xxxx>,<N/S>,<xxx.xxxx>,<E/W>,<xxxx>,<xxx>

  DEBUG CLS, "AeroGPS Details", CR, CR
  PAUSE 250

  FOR recNum = 1 TO records
    GOSUB Load_GPS_Record
    DEBUG DEC recNum, Comma
    DEBUG DEC latDeg, ".", DEC4 latFrac, Comma, "N" + (latNS * 5), Comma
    DEBUG DEC lonDeg, ".", DEC4 lonFrac, Comma, "E" + (lonEW * 18), Comma
    DEBUG DEC altitude, Comma
    DEBUG DEC (speed / 10), ".", DEC1 (speed // 10), CR
  NEXT
  END


' removed to make room for new code
'
'Dump_Graph:
'  ' dump for easy Excel graphing of track
'  ' -- converts "S" and "W" to "-"
'  ' -- put longitude in first column for X axis of X/Y graph
'  ' -- <sign><longitude>,<sign><latitude>,<altitude>,<speed>
'  ' -- <s><xxx.xxxx>,<s><xx.xxxx>,<xxxx>,<xxx>
'
'  DEBUG CLS, "AeroGPS Lon/Lat/Alt/Speed Data", CR
'  DEBUG "(", DEC records, " Records)", CR, CR
'  PAUSE 250
'
'  FOR recNum = 1 TO records
'    GOSUB Load_GPS_Record
'    DEBUG " " + (lonEW * 13), DEC lonDeg, ".", DEC4 lonFrac, Comma
'    DEBUG " " + (latNS * 13), DEC latDeg, ".", DEC4 latFrac, Comma
'    DEBUG DEC altitude, Comma
'    DEBUG DEC (speed / 10), ".", DEC1 (speed // 10), CR
'  NEXT
'  END


' ***********************************************
' Load store GPS records for data dump to screen
' ***********************************************

Load_GPS_Record:
  eeAddr = (recNum - 1) * RecSize + FirstAddr
  eeAddr = eeAddr + 0 : GOSUB Read_Big_EE : flags   = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : latDeg  = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : latFrLo = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : latFrHi = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : lonDeg  = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : lonFrLo = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : lonFrHi = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : altLo   = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : altHi   = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : spdLo   = eeData
  eeAddr = eeAddr + 1 : GOSUB Read_Big_EE : spdHi   = eeData
  RETURN

' *******************************
' Read data from "flat" EE memory
' *******************************

Read_Big_EE:
  IF (eeAddr > MaxAddr) THEN No_Read            ' check for bad eeAddr
  STORE (eeAddr / 2048) + EESlot                ' point to EE slot
  READ (eeAddr // 2048), eeData

No_Read:
  RETURN
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un2000
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« Reply #7 on: October 29, 2008, 07:54:10 19:54 »

Hi

read my file proton and proteus simulations download code and proteus file
used an real gps mouse type attached a virtual usb rs232 port
via prolific chip set


http://www.geocities.com/toshivomifune/

search for GPS

good look!!


Posted on: October 29, 2008, 07:51:59 19:51 - Automerged

download

http://www.geocities.com/toshivomifune/GPS.zip

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