'-------------------------------------------------------------------------------
'                              starter.bas
'       this is an example for readining a Devantech Compass
'                    all output will be on com2
'     There is also an LED on portB.0 that will light if the
'                 direction = north +/- 5 degrees
'-------------------------------------------------------------------------------


$crystal = 14745600
$regfile = "m128def.dat"
$baud1 = 19200
'$sim

'config serial buffer
Config Serialout1 = Buffered , Size = 40
Config Serialin1 = Buffered , Size = 40

'com 2 standard conection
Config Com2 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0

'config  I2C lines for mavric
Config Sda = Portd.1
Config Scl = Portd.0

'this function is used to read the compass value
'declare Functons
Declare Function I2cread8_w(byval I2cnode As Byte , Byval Loc As Byte) As Word


'  Startup int code
I2cinit                                                     'start the I2C buss
Open "com2:" For Random As #2                               'open come port
Enable Interrupts                                           'enable interupts
Config Portb = Output
Portb = 0                                                   'set all low

'varables
Dim Heading As Word                                         'varable to hold compass value
Dim Readable_heading As Single
Const Compass = 192                                         'make address of compass

'start main program
Do
   'small delay of 500mS
   Waitms 500
   Heading = I2cread8_w(compass , 2)                        'read the heading reading from node 192 and locations 2 & 3

'  sence the heading is returned as a word a reading of 90 would come back as "0900"
'  to make it human readable you can copy the heading heading to "readable_heading" and devide it by 10
   Readable_heading = Heading                               'copy first
   Readable_heading = Readable_heading / 10                 'devide after the varable is stored in a single

   ' a bit of math on the reading to see if it is with in +/- 5 degrees of north
   Print #2 , "Heading = " + Str(readable_heading) + Chr(10) + Chr(13)
   If Heading > 3550 Or Heading < 50 Then
      Portb.0 = 1                                           ' within 5 degrees of north then led ON
      Print #2 , "LED on" + Chr(10) + Chr(13)
   Else
      Portb.0 = 0                                           ' greater then 5 degrees then led OFF
      Print #2 , "LED off" + Chr(10) + Chr(13)
   End If
   Print #2 , "" + Chr(10) + Chr(13)                        'blank print to seperate readings
Loop
'end main program

'subs
'------------------------------    I2C    I2C    I2C    I2C    I2C    I2C    I2C    I2C    I2C    I2C    I2C
'8x16
Function I2cread8_w(byval I2cnode As Byte , Loc As Byte) As Word
  Local Lsb As Byte
  Local Msb As Byte
  I2cstart
  I2cwbyte I2cnode
  I2cwbyte Loc
  I2cstart
  Incr I2cnode
  I2cwbyte I2cnode
  I2crbyte Msb , Ack
  I2crbyte Lsb , Nack
  I2cstop
  I2cread8_w = Makeint(lsb , Msb)
End Function