'Display latitude and longitude out of a GPS (NMEA output) on a 16*2 lines
'LCD display using the hitachi HD 44780 controller. Needs the stamp BS2 for
'4800 bauds NMEA. The LCD is wired in 4 bits mode according to the
'application note #1 in the stamp 1 manual. The code for LCD is adapted to
'the BS2 from the same app note. The NMEA input is on PIN 7.


lat var byte(8)		'latitude without last decimal
long var byte(9)	'longitude without last decimal
'time var byte(6)	'time (not used for now)
ns var byte		'North South character
ew var byte		'East West character

E con 5		'LCD Enable pin, 1 = enabled
RS con 4	' LCD Register select pin, 0 = instruction
char var byte	'Character sent to LCD. 
c var byte	'not use anymore I think (?)
ni var byte	'nibble sent to the LCD


begin:

outl = 0		'Clear the output lines
dirl = %01111111	'One input, 7 outputs. 
pause 200		'Wait 200 ms for LCD to reset. 


' Initialize the LCD in accordance with Hitachi's instructions for 4-bit
interface. 

outl = %00000011	'Set to 8-bit operation. 
pulsout E,5		'Send data three times
pause 10		'to initialize LCD. 
pulsout E,5		
pause 10		
pulsout E,5		
pause 10		

outl = %00000010	'Set to 4-bit operation. 
pulsout E,5		 
pulsout E,5
outl = %00001010
pulsout E,5

char = 14		'Set up LCD in accordance with
gosub wr_LCD		'Hitachi instruction manual. 

char = 6		'Turn on cursor and enable
gosub wr_LCD		'left-to-right printing. 

char = 1		'Clear the display. 
gosub wr_LCD

high	RS		'Prepare to send characters. 

start:

' get NMEA data from pin 7, wait for the sentence "$GPGGA" to appear then
skip 8 characters then read a 8 char string in lat .....

serin 7,188+$4000,[wait("$GPGGA"),skip 8 ,str lat\8,skip 1,str ns\1,skip
1,str long\9,skip 1,str ew\1]


'display on the pc screen for debug purpose to test NMEA connection only
'debug str lat\7," ",ns,"   ",str long\8," ",ew,cr 

'put LCD cursor at 1st position on 1st line 
low RS : char=%10000000 : gosub wr_LCD : high RS


char="L" : gosub wr_LCD		'write "LAT N 74°56.45'" on LCD first line 
char="A" : gosub wr_LCD
char="T" : gosub wr_LCD
char=" " : gosub wr_LCD
char=ns  : gosub wr_LCD
char=" " : gosub wr_LCD
char=lat(0) : gosub wr_LCD
char=lat(1) : gosub wr_LCD
char=%11011111    : gosub wr_LCD	'hitachi's code for char "°"
char=lat(2) : gosub wr_LCD
char=lat(3) : gosub wr_LCD
char=lat(4) : gosub wr_LCD
char=lat(5) : gosub wr_LCD
char=lat(6) : gosub wr_LCD
char=lat(7) : gosub wr_LCD
char=39 : gosub wr_LCD			'hitachi's code for char "'"

'move LCD cursor to 1st position on 2d line
low RS : char=%11000000 : gosub wr_LCD : high RS

char="L" : gosub wr_LCD		'write "LNG W 125°56.45'" on LCD second line
char="N" : gosub wr_LCD
char="G" : gosub wr_LCD
char=" " : gosub wr_LCD
char=ew  : gosub wr_LCD

char=long(0) : gosub wr_LCD
char=long(1) : gosub wr_LCD
char=long(2) : gosub wr_LCD
char=%11011111    : gosub wr_LCD
char=long(3) : gosub wr_LCD
char=long(4) : gosub wr_LCD
char=long(5) : gosub wr_LCD
char=long(6) : gosub wr_LCD
char=long(7) : gosub wr_LCD
char=long(8) : gosub wr_LCD
char=39 : gosub wr_LCD
	
goto start

end

' Write the ASCII character in char to LCD. 
'rem: actually not all the codes are exact ASCII match.

wr_LCD:	outl = outl & %00010000
	ni = char/16		'Put high nibble of b3 into b2. 
	outl = outl | ni	'OR the contents of b2 into pins. 
	pulsout E,10		'Blip enable pin. 
	ni = char & %00001111	'Put low nibble of b3 into b2. 
	outl = outl & %00010000	'Clear 4-bit data bus. 
	outl = outl | ni	'OR the contents of b2 into pins.
	pulsout E,10		'Blip enable. 
return