1  """ Display compass heading data from a calibrated magnetometer """
 2  
 3  import time
 4  import math
 5  import board
 6  import busio
 7  import adafruit_lis2mdl
 8  
 9  i2c = busio.I2C(board.SCL, board.SDA)
10  sensor = adafruit_lis2mdl.LIS2MDL(i2c)
11  
12  # You will need the calibration values from your magnetometer calibration
13  # these values are in uT and are in X, Y, Z order (min and max values).
14  #
15  # To get these values run the lis2mdl_calibrate.py script on your device.
16  # Twist the device around in 3D space while it calibrates. It will print
17  # some calibration values like these:
18  # ...
19  # Calibrating - X:    -46.62, Y:    -22.33, Z:    -16.94 uT
20  # ...
21  # Calibration complete:
22  # hardiron_calibration = [[-63.5487, 33.0313], [-40.5145, 53.8293], [-43.7153, 55.5101]]
23  #
24  # You need t copy your own value for hardiron_calibration from the output and paste it
25  # into this script here:
26  hardiron_calibration = [[-61.4879, 34.4782], [-43.6714, 53.5662], [-40.7337, 52.4554]]
27  
28  
29  # This will take the magnetometer values, adjust them with the calibrations
30  # and return a new array with the XYZ values ranging from -100 to 100
31  def normalize(_magvals):
32      ret = [0, 0, 0]
33      for i, axis in enumerate(_magvals):
34          minv, maxv = hardiron_calibration[i]
35          axis = min(max(minv, axis), maxv)  # keep within min/max calibration
36          ret[i] = (axis - minv) * 200 / (maxv - minv) + -100
37      return ret
38  
39  
40  while True:
41      magvals = sensor.magnetic
42      normvals = normalize(magvals)
43      print("magnetometer: %s -> %s" % (magvals, normvals))
44  
45      # we will only use X and Y for the compass calculations, so hold it level!
46      compass_heading = int(math.atan2(normvals[1], normvals[0]) * 180.0 / math.pi)
47      # compass_heading is between -180 and +180 since atan2 returns -pi to +pi
48      # this translates it to be between 0 and 360
49      compass_heading += 180
50  
51      print("Heading:", compass_heading)
52      time.sleep(0.1)