Publish files

software/accelerometer-calibration/accelerometer-calibration.ino

@@ -0,0 +1,118 @@
+// This program can be used to get the offsets and scaling factors for the gyro and accelerometer. This cannot be done
+// automatically. The cube must be placed in six different orientations, corresponding to each axis facing up and down.
+// Calibration offsets should initially be set to zero. Use the methodology as described in Analog Devices AN-1057,
+// which may be found here: https://www.analog.com/en/app-notes/an-1057.html. In particular, equations 17 and 18.
+
+#include <Wire.h>
+#include <ICM20948_WE.h>
+#define ICM20948_ADDR 0x68
+
+TwoWire wirePort = TwoWire(0);
+ICM20948_WE myIMU = ICM20948_WE(&wirePort);
+
+void setup() {
+  // Set up serial
+  Serial.begin(921600);
+
+  // Set up I2C on pins 47 (SDA) and 21 (SCL) at 400 kHz
+  wirePort.begin(47, 21, 400000);
+  
+  // Initialize IMU
+  if(!myIMU.init()){
+    Serial.println("ICM20948 does not respond");
+  }
+  else{
+    Serial.println("ICM20948 is connected");
+  }
+  
+  // Set accelerometer and gyroscope ranges
+  myIMU.setAccRange(ICM20948_ACC_RANGE_2G);
+  myIMU.setGyrRange(ICM20948_GYRO_RANGE_2000);
+  
+  // Set digital low pass filter setting such that noise is minimized (lowest cut-off frequency)
+  myIMU.setAccDLPF(ICM20948_DLPF_6);
+  myIMU.setGyrDLPF(ICM20948_DLPF_6); 
+  
+  // Disable sample rate divider
+  myIMU.setAccSampleRateDivider(0);
+  myIMU.setGyrSampleRateDivider(0);
+}
+
+unsigned long timer;
+xyzFloat acc, gyr;
+float ax, ay, az, gx, gy, gz;
+
+// Calibration offsets
+const float b_gyr_x = 0.74;
+const float b_gyr_y = 0.66;
+const float b_gyr_z = -0.45;
+
+// IMU accelerator offsets and gain
+const float b_acc_x = -6;
+const float b_acc_y = -215;
+const float b_acc_z = 161;
+const float f_acc_x = 1672.7;
+const float f_acc_y = 1673.3;
+const float f_acc_z = 1691.5;
+
+void loop() {
+  // Start a timer
+  timer = millis();
+
+  // Measure 1000 samples and average them
+  for(int i = 0; i < 1000; i++) {
+    myIMU.readSensor();
+    acc = myIMU.getAccRawValues();
+    gyr = myIMU.getGyrValues();
+
+    ax += acc.x / 1000;
+    ay += acc.y / 1000;
+    az += acc.z / 1000;
+    gx += gyr.x / 1000;
+    gy += gyr.y / 1000;
+    gz += gyr.z / 1000;
+
+    // Print raw and calibrated values in last cycle
+    if(i == 999) {
+      Serial.print("Raw: Acc: ");
+      Serial.print(ax);
+      Serial.print(", ");
+      Serial.print(ay);
+      Serial.print(", ");
+      Serial.print(az);
+      Serial.print(", ");
+      Serial.print("gyr: ");
+      Serial.print(gx);
+      Serial.print(", ");
+      Serial.print(gy);
+      Serial.print(", ");
+      Serial.println(gz);
+
+  	  // Equation 19 in AD AN-1057 is used here
+      Serial.print("Calibrated: Acc: ");
+      Serial.print((ax - b_acc_x) / f_acc_x);
+      Serial.print(", ");
+      Serial.print((ay - b_acc_y) / f_acc_y);
+      Serial.print(", ");
+      Serial.print((az - b_acc_z) / f_acc_z);
+      Serial.print(", ");
+      Serial.print("gyr: ");
+      Serial.print(gx - b_gyr_x);
+      Serial.print(", ");
+      Serial.print(gy - b_gyr_y);
+      Serial.print(", ");
+      Serial.println(gz - b_gyr_z);
+    }
+  }
+
+  // Print how long it took to get 1000 measurements
+  Serial.print("Took "); Serial.print(millis() - timer); Serial.println(" ms.");
+
+  // Reset averages
+  ax = 0;
+  ay = 0;
+  az = 0;
+  gx = 0;
+  gy = 0;
+  gz = 0;
+}