GPS, NEMA extraction for Picaxe

M

Marcwolf

Senior Member
GPS, NMEA extraction for Picaxe

Hi
This is a GPS extraction routine that make use of the scratchpad for pointer operations. I can be modified to use
stanadard memory as well using th BPTR

I've corrected the format of the code after a fight with the editor.

Enjoy
Code: 
; *******************************
; ***** GPS I2C Slave       *****
; *******************************
;    Filename: GPS_Pixaxe  
;    Date:   04/09/2011 
;    File Version: 1.5 
;    Written by:  Marcwolf 
;    Function:  Decode GPS Signals
;    Last Revision:
;    Target PICAXE: 28X2
; ******************************* 
' This should work on any Picaxe with a scratchpad and variable space
' The scratchpad is split into 2 parts
' 0 to 256 (changable as we only really need 130.. But this is only the 
' start for this project.
' and 256 + for info retrieved from the GPS unit (EM406A but can be any)
' The target conept is to have a Slave I2C PicAxe that will gather 
' GPS, Temp, Voltage etc data and present it in the scratchpad
' ready for the master to collect it.
' There is no special speed constraints on this so no SetFreq is needed
Symbol ptrSer = w26  ' Pointer for incoming serial
Symbol ptrI2C = w27  ' Pointer for outgoing I2C
Symbol SerPoke = 256 ' Start of the Scratchpad area of Serial
Symbol I2CPoke = b49 ' Slave I2C store ptr for Master to grab
Symbol PokePtr = b51 ' Temp area for extraction
Symbol Commas = b50  ' # of comma's to start from
Symbol GPSPort = b.7 ' Where is the GPS
' Starts of routine
GPS:
' Clear scratchpad to spaces ready for data
ptr =0: for b0 = 0 to 150 : ptr = b0 : @ptr = 32 : next 
ptr=SerPoke ' Set pointer to start of GPS store
' Get the GPS info in. Had issues with HSERIn so now just use the scratchpad
serin GPSPort,T4800,("GPGGA"),@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc
pause 100 ' pause to take processing breath
' Get the information
' Search GPS scratchpad for the number of Comma's
' then put the resulting text into the scratchpad
' starting at potion I2CPoke
Commas = 1: gosub GetString : I2CPoke = 0   : gosub PutString ' Time
Commas = 2: gosub GetString : I2CPoke = 30  : gosub PutString' Lat
Commas = 3: gosub GetString : I2CPoke = 110 : gosub PutString ' E/W
Commas = 4: gosub GetString : I2CPoke = 45  : gosub PutString ' Long 
Commas = 5: gosub GetString : I2CPoke = 115 : gosub PutString ' N/S
Commas = 9: gosub GetString : I2CPoke = 60  : gosub PutString ' MSL
Commas = 10:gosub GetString : I2CPoke = 120 : gosub PutString ' Meters for MSL
' Same again
ptr=SerPoke
serin GPSPort,T4800,("GPRMC"),@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc
Pause 100
Commas = 2: gosub GetString : I2CPoke = 125 : gosub PutString ' GPS Fix
Commas = 7: gosub GetString : I2CPoke = 75  : gosub PutString ' speed
Commas = 8: gosub GetString : I2CPoke = 90  : gosub PutString ' Direction
Commas = 9: gosub GetString : I2CPoke = 15   : gosub PutString ' Date
' now read out the scratchpad to simulate a I2C Master Read
ptr =0: for b0 = 0 to 150 : ptr = b0: sertxd(@ptr) : next : sertxd(CR,LF)' you can add other functions and processes.
GOTO GPS
GetString:' Clear temp mem - 15 Bytes
for b0 = 80 to 95: poke b0,32: next
' Search along the scratchpad for X number of comma's
ptrSer =  SerPoke
ptr = SerPoke -1
b2 = 0  ' count of comma's
do  ' look until we find the comma we are looking for  
 if @ptrinc = "," then ' We found a comma
    inc b2     
  if b2 = Commas then exit ' Are we X Comma's along. If so then exit  
 end if
loop' We are at the X comma, check that there is a next character
if @ptrinc = "," then return : end if ' empty string as in ,,
dec ptr :PokePtr = 80 ' Step back one position and reset the temp memory ptr
' Now get the string to the next comma
do 
 b0 = @ptrinc ' Get the valid character  
if b0 = "," then  ' Are we at the next delimiter  
  exit ' ok jump out of loop 
 else     poke PokePtr, b0 ' put the actual value into the memory store    
 inc  PokePtr ' increment memory store ptr  
end if
loop' nothing more to do.  GPS extract is in bytes 80 to 95 ready for processing
return  
PutString:' put the memory store back into the correct position of the  SLAVE I2C storeptr = I2CPoke  ' set pointer to the I2C slave area
For b0 = 80 to 95 ' loop through memory store 
  peek b0,b1 ' get the info
   if b1 = 32 then return: end if ' A space - then we are at the end of the string 
  @ptrinc  = b1 ' poke the value into the I2C store
Next
Return
 
Last edited:
M

MPep

Senior Member
You must mean NMEA, not NEMA. NEMA is a totally different mechanical standard.

Thanks for posting though.
 
P

papaof2

Senior Member
Marcwolf said:
Hi
This is a GPS extraction routine that make use of the scratchpad for pointer operations. I can be modified to use
stanadard memory as well using th BPTR

Enjoy
Code: 
; *******************************; ***** GPS I2C Slave       *****; *******************************;    Filename: GPS_Pixaxe  ;    Date:   04/09/2011 ;    File Version: 1.5 ;    Written by:  Marcwolf ;    Function:  Decode GPS Signals;    Last Revision:;    Target PICAXE: 28X2; ******************************* ' This should work on any Picaxe with a scratchpad and variable space' The scratchpad is split into 2 parts' 0 to 256 (changable as we only really need 130.. But this is only the ' start for this project.' and 256 + for info retrieved from the GPS unit (EM406A but can be any)' The target conept is to have a Slave I2C PicAxe that will gather ' GPS, Temp, Voltage etc data and present it in the scratchpad' ready for the master to collect it.' There is no special speed constraints on this so no SetFreq is neededSymbol ptrSer = w26  ' Pointer for incoming serialSymbol ptrI2C = w27  ' Pointer for outgoing I2CSymbol SerPoke = 256 ' Start of the Scratchpad area of SerialSymbol I2CPoke = b49 ' Slave I2C store ptr for Master to grabSymbol PokePtr = b51 ' Temp area for extractionSymbol Commas = b50  ' # of comma's to start fromSymbol GPSPort = b.7 ' Where is the GPS' Starts of routineGPS:' Clear scratchpad to spaces ready for dataptr =0: for b0 = 0 to 150 : ptr = b0 : @ptr = 32 : next ptr=SerPoke ' Set pointer to start of GPS store' Get the GPS info in. Had issues with HSERIn so now just use the scratchpadserin GPSPort,T4800,("GPGGA"),@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrincpause 100 ' pause to take processing breath' Get the information' Search GPS scratchpad for the number of Comma's' then put the resulting text into the scratchpad' starting at potion I2CPokeCommas = 1: gosub GetString : I2CPoke = 0   : gosub PutString ' TimeCommas = 2: gosub GetString : I2CPoke = 30  : gosub PutString ' LatCommas = 3: gosub GetString : I2CPoke = 110 : gosub PutString ' E/WCommas = 4: gosub GetString : I2CPoke = 45  : gosub PutString ' Long Commas = 5: gosub GetString : I2CPoke = 115 : gosub PutString ' N/SCommas = 9: gosub GetString : I2CPoke = 60  : gosub PutString ' MSLCommas = 10:gosub GetString : I2CPoke = 120 : gosub PutString ' Meters for MSL' Same againptr=SerPokeserin GPSPort,T4800,("GPRMC"),@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrincPause 100Commas = 2: gosub GetString : I2CPoke = 125 : gosub PutString ' GPS FixCommas = 7: gosub GetString : I2CPoke = 75  : gosub PutString ' speedCommas = 8: gosub GetString : I2CPoke = 90  : gosub PutString ' DirectionCommas = 9: gosub GetString : I2CPoke = 15   : gosub PutString ' Date' now read out the scratchpad to simulate a I2C Master Readptr =0: for b0 = 0 to 150 : ptr = b0: sertxd(@ptr) : next : sertxd(CR,LF)' you can add other functions and processes.GOTO GPSGetString:' Clear temp mem - 15 Bytesfor b0 = 80 to 95: poke b0,32: next' Search along the scratchpad for X number of comma'sptrSer =  SerPokeptr = SerPoke -1b2 = 0  ' count of comma'sdo  ' look until we find the comma we are looking for  if @ptrinc = "," then ' We found a comma    inc b2     if b2 = Commas then exit ' Are we X Comma's along. If so then exit  end ifloop' We are at the X comma, check that there is a next characterif @ptrinc = "," then return : end if ' empty string as in ,,dec ptr :PokePtr = 80 ' Step back one position and reset the temp memory ptr' Now get the string to the next commado  b0 = @ptrinc ' Get the valid character  if b0 = "," then  ' Are we at the next delimiter    exit ' ok jump out of loop  else     poke PokePtr, b0 ' put the actual value into the memory store     inc  PokePtr ' increment memory store ptr  end ifloop' nothing more to do.  GPS extract is in bytes 80 to 95 ready for processingreturn  PutString:' put the memory store back into the correct position of the  SLAVE I2C storeptr = I2CPoke  ' set pointer to the I2C slave areaFor b0 = 80 to 95 ' loop through memory store   peek b0,b1 ' get the info   if b1 = 32 then return: end if ' A space - then we are at the end of the string   @ptrinc  = b1 ' poke the value into the I2C storenextreturn
Click to expand...
Look at the semi-colon locations. The code has no CR/LF's in it and thus can't be used.

John
 
W

westaust55

Moderator
MPep said:
You must mean NMEA, not NEMA. NEMA is a totally different mechanical standard.

Thanks for posting though.
Click to expand...
Oh heck,
. . . .and I thought it was electrical

National Electrical Manufacturers Association

now where was that glass house ;)
 
P

papaof2

Senior Member
This passes the syntax check. I don't have a 28X2 + GPS near this computer so I didn't do a hardware check.

Code: 
; *******************************
; ***** GPS I2C Slave       *****
; *******************************
;    Filename: GPS_Pixaxe  
;    Date:   04/09/2011 
;    File Version: 1.5 
;    Written by:  Marcwolf 
;    Function:  Decode GPS Signals
;    Last Revision:
;    Target PICAXE: 28X2
; ******************************* 
' This should work on any Picaxe with a scratchpad and variable space
' The scratchpad is split into 2 parts
' 0 to 256 (changable as we only really need 130.. But this is only the 
' start for this project.
' and 256 + for info retrieved from the GPS unit (EM406A but can be any)
' The target conept is to have a Slave I2C PicAxe that will gather 
' GPS, Temp, Voltage etc data and present it in the scratchpad
' ready for the master to collect it.
' There is no special speed constraints on this so no SetFreq is needed
Symbol ptrSer = w26  ' Pointer for incoming serial
Symbol ptrI2C = w27  ' Pointer for outgoing I2C
Symbol SerPoke = 256 ' Start of the Scratchpad area of Serial
Symbol I2CPoke = b49 ' Slave I2C store ptr for Master to grab
Symbol PokePtr = b51 ' Temp area for extraction
Symbol Commas = b50  ' # of comma's to start from
Symbol GPSPort = b.7 ' Where is the GPS
' Starts of routine
GPS:
' Clear scratchpad to spaces ready for data
ptr =0: for b0 = 0 to 150 : ptr = b0 : @ptr = 32 : next 
ptr=SerPoke ' Set pointer to start of GPS store
' Get the GPS info in. Had issues with HSERIn so now just use the scratchpad
serin GPSPort,T4800,("GPGGA"),@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc
pause 100 ' pause to take processing breath
' Get the information
' Search GPS scratchpad for the number of Comma's
' then put the resulting text into the scratchpad
' starting at potion I2CPoke
Commas = 1: gosub GetString : I2CPoke = 0   : gosub PutString ' Time
Commas = 2: gosub GetString : I2CPoke = 30  : gosub PutString' Lat
Commas = 3: gosub GetString : I2CPoke = 110 : gosub PutString ' E/W
Commas = 4: gosub GetString : I2CPoke = 45  : gosub PutString ' Long 
Commas = 5: gosub GetString : I2CPoke = 115 : gosub PutString ' N/S
Commas = 9: gosub GetString : I2CPoke = 60  : gosub PutString ' MSL
Commas = 10:gosub GetString : I2CPoke = 120 : gosub PutString ' Meters for MSL
' Same again
ptr=SerPoke
serin GPSPort,T4800,("GPRMC"),@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc,@ptrinc
Pause 100
Commas = 2: gosub GetString : I2CPoke = 125 : gosub PutString ' GPS Fix
Commas = 7: gosub GetString : I2CPoke = 75  : gosub PutString ' speed
Commas = 8: gosub GetString : I2CPoke = 90  : gosub PutString ' Direction
Commas = 9: gosub GetString : I2CPoke = 15   : gosub PutString ' Date
' now read out the scratchpad to simulate a I2C Master Read
ptr =0: for b0 = 0 to 150 : ptr = b0: sertxd(@ptr) : next : sertxd(CR,LF)' you can add other functions and processes.
GOTO GPS
GetString:' Clear temp mem - 15 Bytes
for b0 = 80 to 95: poke b0,32: next
' Search along the scratchpad for X number of comma's
ptrSer =  SerPoke
ptr = SerPoke -1
b2 = 0  ' count of comma's
do  ' look until we find the comma we are looking for  
	if @ptrinc = "," then ' We found a comma
    inc b2     
		if b2 = Commas then exit ' Are we X Comma's along. If so then exit  
	end if
loop' We are at the X comma, check that there is a next character
if @ptrinc = "," then return : end if ' empty string as in ,,
dec ptr :PokePtr = 80 ' Step back one position and reset the temp memory ptr
' Now get the string to the next comma
do 
 b0 = @ptrinc ' Get the valid character  
if b0 = "," then  ' Are we at the next delimiter  
  exit ' ok jump out of loop 
 else     poke PokePtr, b0 ' put the actual value into the memory store    
 inc  PokePtr ' increment memory store ptr  
end if
loop' nothing more to do.  GPS extract is in bytes 80 to 95 ready for processing
return  

PutString:' put the memory store back into the correct position of the  SLAVE I2C storeptr = I2CPoke  ' set pointer to the I2C slave area
For b0 = 80 to 95 ' loop through memory store 
  peek b0,b1 ' get the info
   if b1 = 32 then return: end if ' A space - then we are at the end of the string 
  @ptrinc  = b1 ' poke the value into the I2C store
Next
Return
The abbreviation is NMEA for National Marine Electronics Association, the group behind the protocol of the GPS sentences.

John
 
M

MPep

Senior Member
Okay, I stand corrected. I had, though, seen another NEMA. Can't remember where though, it was a few years ago.
In NMEA, National means USA. ie they started it.
 
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