Add COMPASS code and sample, color compass app

python/EDS.py

@@ -220,3 +220,21 @@ class Clock:
         self.i2.start(self.a, 1)
         print(list(self.i2.read(16)))
         self.i2.stop()
+
+class Magnet:
+    """ MAGNET is an ST LIS3MDL 3-axis magnetometer """
+    def __init__(self, i2, a = 0x1c):
+        self.i2 = i2
+        self.a = a
+        self.i2.regwr(self.a, 0x22, 0) # CTRL_REG3 operating mode 0: continuous conversion
+
+    def rd(self):
+        """ Read the measurement STATUS_REG and OUT_X,Y,Z """
+        return self.i2.regrd(self.a, 0x27, "<B3h")
+
+    def measurement(self):
+        """ Wait for a new field reading, return the (x,y,z) """
+        while True:
+            (status, x, y, z) = self.rd()
+            if status & 8:
+                return (x, y, z)

python/samples/EDS-MAGNET.py

@@ -0,0 +1,12 @@
+import sys
+import struct
+import time
+
+from i2cdriver import I2CDriver, EDS
+
+if __name__ == '__main__':
+    i2 = I2CDriver(sys.argv[1])
+
+    d = EDS.Magnet(i2)
+    while 1:
+        print(d.measurement())

python/samples/EDS-POT.py

@@ -6,7 +6,6 @@ from i2cdriver import I2CDriver, EDS
 
 if __name__ == '__main__':
     i2 = I2CDriver(sys.argv[1])
-    i2.scan()
 
     d = EDS.Pot(i2)
 

python/samples/EDS-color-compass.py

@@ -0,0 +1,32 @@
+"""
+Demo of a simple combination of parts from Electric Dollar Store:
+
+* MAGNET - 3-axis magnetometer
+* LED - RGB LED
+
+This demo takes the compass direction, and uses it to set the LED's
+color. So as you move the module around, the color changes according to
+its direction.  There is a direction that is pure red, another that is
+pure green, etc.
+
+https://electricdollarstore.com
+
+"""
+import sys
+import struct
+import time
+
+from i2cdriver import I2CDriver, EDS
+
+if __name__ == '__main__':
+    i2 = I2CDriver(sys.argv[1])
+
+    magnet = EDS.Magnet(i2)
+    led = EDS.LED(i2)
+    led.rgb(0, 0, 0)
+    while 1:
+        (x, y, z) = magnet.measurement()
+        r = max(0, min(255, (x + 4000) // 32))
+        g = max(0, min(255, (y + 4000) // 32))
+        b = max(0, min(255, (z + 4000) // 32))
+        led.rgb(r, g, b)