Code:
'****************************************************************
'* Name : COMPASS_818.BAS *
'* Author : [select VIEW...EDITOR OPTIONS] *
'* Notice : Copyright (c) 2014 [select VIEW...EDITOR OPTIONS] *
'* : All Rights Reserved *
'* Date : 24/08/2014 *
'* Version : 1.0 *
'* Notes : *
'* : *
'****************************************************************
' LCD should be connected as follows:
' LCD PIC
' DB4 PortA.0
' DB5 PortA.1
' DB6 PortA.2
' DB7 PortA.3
' RS PortA.4 (add 4.7K (10k)pullup resistor to 5 volts)
' E PortB.3
' RW Ground
' Vdd 5 volts
' Vss Ground
' Vo 5K potentiometer (or ground)
' DB0-3 No connect
adcon1 = 7 ' Turns Analogs off
DEFINE OSC 12 'Set oscillator in MHz
'OSCCON = $70
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 6
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 7
' -----[ Pins/Constants/Variables ]-------------------------------------------
SDA var portb.1 'transceives to/from SDA
SCL var portb.4 'sends clock pulses
WRITE_DATA CON $3C 'Used to perform a Write operation
READ_DATA CON $3D 'Used to perform a Read operation
MODE CON $02 'Read/Write Register, Selects the operating mode. Default = Single measurement
'Send $3C $02 $00 on power up to change to continuous measurement mode.
X_MSB CON $03 'Read Register, Output of X MSB 8-bit value.
X_LSB CON $04 'Read Register, Output of X LSB 8-bit value.
Z_MSB CON $05 'Read Register, Output of Z MSB 8-bit value.
Z_LSB CON $06 'Read Register, Output of Z LSB 8-bit value.
Y_MSB CON $07 'Read Register, Output of Y MSB 8-bit value.
Y_LSB CON $08 'Read Register, Output of Y LSB 8-bit value.
Cont_Mode CON $0
SCALEFACTOR CON 4081 'SCALEFACTOR = 65536 * (255/4095) = 4081
SCALEOFFSET CON 2048 'The output range of the HMC5883L is -2048 to 2047; therefore to get a 0 (LOWRANGE)to 4095 range
'to 4095 (HIGHRANGE) range 2048 must be added to the sensor value.
ATNFACTOR CON 127 'the ATN function input range is -127 TO 127. In order to get the positive scaled range of
'0 to 255 into the range of -127 to 127, 127 must be subtracted.
LOWRANGE CON 0 'see SCALEOFFSET
HIGHRANGE CON 4095 'see SCALEOFFSET
X VAR byte 'x sensor measured value
Y VAR byte 'y sensor measured value
Z VAR byte 'z sensor measured value
READX VAR WORD
READY VAR WORD
READZ VAR WORD
brads VAR Word 'angle in brads
degr VAR Word 'angle in degrees
azimuth VAR Word 'value calculated using X ATN -Y
' -----[ Main Routine ]-------------------------------------------------------
PAUSE 500 ' Give sensor needed power up time
I2CWRITE SDA,SCL,WRITE_DATA,MODE,[Cont_Mode] ' Send continuous output command
DO
GOSUB GetRawReading ' Get RAW Compass reading
'RAW X,Y,Z data...
'Lcdout $fe, 1 ' Clear LCD screen
'Lcdout "X=",SDEC READX ," Y=",SDEC READY
'Lcdout $fe, $C0, "Z=",SDEC READZ
'DEBUG HOME, "RAW X,Y,Z", CR
'DEBUG "X = ",11, SDEC x, CR
'DEBUG "Y = ",11, SDEC y, CR
'DEBUG "Z = ",11, SDEC z, CR ' Print angle
'DEBUG CR
'Calculate Azimuth
GOSUB GetAzimuth
'Calculated Heading in Degrees
brads = azimuth 'get angle
'degr = brads */ 361 'convert to degrees
degr = brads*360/256
Lcdout $fe, $C0, "Degrees =",SDEC degr
'DEBUG CR
'DEBUG "Heading in NORTH, EAST, SOUTH, and WEST clockwise from NORTH:", CLREOL, CR, CR
'DEBUG "Degree " ,11, SDEC degr, CR 'display degrees
GOSUB GetHeading
LOOP
' -----[ Subroutines ]--------------------------------------------------------
GetRawReading: 'Compass module subroutine
PAUSE 400 'Wait for new data to become available
I2CREAD SDA,SCL,READ_DATA, X_MSB,[READX.HIGHBYTE] 'Read the data starting at x_msb 3
I2CREAD SDA,SCL,READ_DATA ,X_LSB,[READX.lowBYTE]
'Do the same for Z and Y:
I2CREAD SDA,SCL,READ_DATA, Z_MSB,[READZ.HIGHBYTE]
I2CREAD SDA,SCL,READ_DATA ,Z_LSB,[READZ.lowBYTE]
I2CREAD SDA,SCL,READ_DATA, Y_MSB,[READY.HIGHBYTE]
I2CREAD SDA,SCL,READ_DATA ,Y_LSB,[READY.lowBYTE]
RETURN
GetAzimuth:
'The output range of the HMC5883L is -2048 to 2047 and the input range of the ATN function
'is -127 to 127. I used the method to scale the output to the input discribed in Parallax's Smart
'Sensors Student Guide v1 starting on page 76.
'SCALEFACTOR = 65536 * (255/4095) = 4081
'SCALEOFFSET = 2048
'ATNFACTOR = 127
'LOWRANGE = 0
'HIGRANGE = 4095 (2048 + 2047 = 4095)
'x = x + SCALEOFFSET
'x = (x MIN LOWRANGE MAX HIGHRANGE) ** SCALEFACTOR - ATNFACTOR
'y = y + SCALEOFFSET
'y = (y MIN LOWRANGE MAX HIGHRANGE) ** SCALEFACTOR - ATNFACTOR
x = readx >>4
Y = readY >>4
Z = readZ >>4
'DEBUG "SCALED X,Y", CR
'DEBUG "X = ",11, SDEC x, CR
'DEBUG "Y = ",11, SDEC y, CR
'azimuth = x ATN -y
azimuth = ( x ATN -y) */ 360
Lcdout $fe, 1 ' Clear LCD screen
Lcdout "Azimuth=",SDEC azimuth
'DEBUG "Azimuth ",11, SDEC azimuth, CR ' display scaled azimuth
'DEBUG "COS Azimuth ",11, SDEC COS azimuth, CR ' display scaled cos azimuth
RETURN
GetHeading:
'Gives a heading in North, South, East and West.
IF degr = 90 THEN
'Lcdout "North"
'DEBUG "NORTH"
'DEBUG CLREOL
ENDIF
IF degr = 0 THEN
'Lcdout "East"
'DEBUG "EAST"
'DEBUG CLREOL
ENDIF
IF degr = 270 THEN
'Lcdout "South"
'DEBUG "SOUTH"
'DEBUG CLREOL
ENDIF
IF degr = 180 THEN
'Lcdout "West"
'DEBUG "WEST"
'DEBUG CLREOL
ENDIF
RETURN
Re: HMC5883L Magnetometer chip Possibilities.
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