Merge pull request #909 from siddacious/lsm303_guide_update

code updates for lsm303 guide

Author: ladyada

LSM303/lsm303agr_combined.py

@@ -0,0 +1,15 @@
+from time import sleep
+import board
+import busio
+import adafruit_lsm303_accel
+import adafruit_lsm303agr_mag
+
+i2c = busio.I2C(board.SCL, board.SDA)
+mag = adafruit_lsm303agr_mag.LSM303AGR_Mag(i2c)
+accel = adafruit_lsm303_accel.LSM303_Accel(i2c)
+
+while True:
+    print("Acceleration (m/s^2): X=%0.3f Y=%0.3f Z=%0.3f"%accel.acceleration)
+    print("Magnetometer (micro-Teslas)): X=%0.3f Y=%0.3f Z=%0.3f"%mag.magnetic)
+    print("")
+    sleep(0.5)

LSM303/servo_calibration/servo_calibration.ino

@@ -0,0 +1,12 @@
+#include <Servo.h> 
+Servo servo;  
+
+void setup() 
+{ 
+  servo.attach(9);  // attaches the servo on pin 9 to the servo object 
+  servo.write(90);  // change this value to achieve minimum rotation!
+} 
+ 
+void loop() 
+{ 
+}

LSM303/servo_compass/servo_compass.ino

@@ -0,0 +1,86 @@
+// **********************************************
+// Zax-O-Meter Sketch 
+// for the Adafruit LSM303 Magnetometer Breakout
+//
+// Written by Bill Earl for Adafruit Industries
+//
+// **********************************************
+
+#include <Wire.h>
+#include <Adafruit_Sensor.h>
+#include <Adafruit_LSM303AGR_Mag.h>
+
+//Uncomment this line and comment out the above for the LSM303DLH
+//#include <Adafruit_LSM303DLH_Mag.h>
+#include <Servo.h>
+
+/* Assign a unique ID to this sensor at the same time */
+Adafruit_LSM303AGR_Mag_Unified mag = Adafruit_LSM303AGR_Mag_Unified(12345);
+//Uncomment this line and comment out the above for the LSM303DLH
+//Adafruit_LSM303DLH_Mag_Unified mag = Adafruit_LSM303AGR_Mag_Unified(12345);
+
+// This is our continuous rotation servo
+Servo servo;
+
+// Pi for calculations - not the raspberry type
+const float Pi = 3.14159;
+
+// This is the value that gives you minimal rotation on
+// a continuous rotation servo.  It is usually about 90.
+// adjust this value to give minimal rotation for your servo
+const float ServoNeutral = 90;  
+
+// This is the desired direction of travel
+// expressed as a 0-360 degree compass heading
+// 0.0 = North
+// 90.0 = East
+// 180.0 = South
+// 270 = West
+const float targetHeading = 0.0;
+
+
+void setup(void) 
+{
+  Serial.begin(115200);
+  Serial.println("Magnetometer Test"); Serial.println("");
+  
+  /* Initialise the sensor */
+  if(!mag.begin())
+  {
+    /* There was a problem detecting the LSM303 ... check your connections */
+    Serial.println("Ooops, no LSM303 detected ... Check your wiring!");
+    while(1);
+  }
+  
+  servo.attach(9);  // Attach servo to pin 9
+
+}
+
+void loop(void) 
+{
+  /* Get a new sensor event */ 
+  sensors_event_t event; 
+  mag.getEvent(&event);
+     
+  // Calculate the angle of the vector y,x
+  float heading = (atan2(event.magnetic.y,event.magnetic.x) * 180) / Pi;
+  // Normalize to 0-360
+  if (heading < 0)
+  {
+    heading = 360 + heading;
+  }
+  
+  // Calculate the error between tha measured heading and the target heading.
+  float error = heading - targetHeading;
+  if (error > 180)
+  {
+    error = error - 360;  // for angles > 180, correct in the opposite direction.
+  }
+  // A non-zero difference between the heading and the 
+  // targetHeading will bias the servoNeutral value and 
+  // cause the servo to rotate back toward the targetHeading.
+  // The divisor is to reduce the reaction speed and avoid oscillations
+  servo.write(ServoNeutral + error / 4 );
+
+  delay(40);
+}