Eric Van den Bulck
Library for setting and reading the Pololu minIMU 9 v2 sensor
Diff: IMU.cpp
- Revision:
- 0:7b70a3ed96c1
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/IMU.cpp Sat Oct 26 11:52:29 2013 +0000
@@ -0,0 +1,167 @@
+/**
+ * @author Eric Van den Bulck
+ *
+ * @section LICENSE
+ *
+ * Copyright (c) 2010 ARM Limited
+ *
+ * @section DESCRIPTION
+ *
+ * Pololu MinIMU-9 v2 sensor:
+ * L3GD20 three-axis digital output gyroscope.
+ * LSM303 three-axis digital accelerometer and magnetometer
+ *
+ * Information to build this library:
+ * 1. The Arduino libraries for this sensor from the Pololu and Adafruit websites, available at gitbub.
+ * https://github.com/adafruit/Adafruit_L3GD20
+ * https://github.com/pololu/L3G/tree/master/L3G
+ * 2. The Rasberry Pi code at https://github.com/idavidstory/goPiCopter/tree/master/io/sensors
+ * https://github.com/idavidstory/goPiCopter/tree/master/io/sensors
+ * 3. Information on how to write libraries: http://mbed.org/cookbook/Writing-a-Library
+ * 4. Information on I2C control: http://mbed.org/users/mbed_official/code/mbed/
+ * 5. The Youtube videos from Brian Douglas (3 x 15') at http://www.youtube.com/playlist?list=PLUMWjy5jgHK30fkGrufluENJqZmLZkmqI
+ * http://www.x-io.co.uk/open-source-imu-and-ahrs-algorithms/
+ * Reading an IMU Without Kalman: The Complementary Filter: http://www.pieter-jan.com/node/11
+ * setup info on the minIMU-9 v2 on http://forum.pololu.com/viewtopic.php?f=3&t=4801&start=30
+ */
+
+#include "mbed.h"
+#include "IMU.h"
+
+IMU::IMU(PinName sda, PinName scl) : _i2c(sda, scl) {
+ _i2c.frequency(400000); /* 400kHz, fast mode. */
+}
+
+char IMU::init(void) /* returns error upon a non-zero return */
+{
+ char ack, rx, tx[2];
+ double pi, a, A;
+
+// 1. Initialize selected registers: 2c.read and i2c.write return 0 on success (ack)
+// --------------------------------
+//
+// 1.a Enable L3DG20 gyrosensor and set operational mode:
+// CTRL_REG1: set to 0x1F = 0001-1111 --> enable sensor, DR= 95Hz, LPF-Cut-off-freq=25Hz.
+// CTRL_REG1: set to 0x5F = 0101-1111 --> enable sensor, DR=190Hz, LPF-Cut-off-freq=25Hz.
+// CTRL_REG4: left at default = 0x00 --> Full Scale = 250 degrees/second --> Sensitivity = 0.00875 dps/digit.
+ address = L3GD20_ADDR;
+ tx[0] = L3GD20_CTRL_REG1; // address contrl_register 1
+ tx[1] = 0x1F; // 00-01-1-111 enable sensor and set operational mode.
+ ack = _i2c.write(address, tx, 2);
+ ack |= _i2c.write(address, tx, 1);
+ ack |= _i2c.read(address+1, &rx, 1); if (rx != 0x1F) ack |= 1;
+//
+// 1.b Enable LSM303 accelerometer and set operational mode:
+// CTRL_REG1: set to 0x37 = 0011 0111 --> DR = 25Hz & enable sensor
+// CTRL_REG1: set to 0x47 = 0100 0111 --> DR = 50Hz & enable sensor
+// CTRL_REG1: set to 0x57 = 0101 0111 --> DR = 100Hz & enable sensor
+// CTRL_REG1: set to 0x77 = 0111 0111 --> DR = 200Hz & enable sensor
+// CTRL_REG4: set to 0x08 = 0000 1000 --> Full Scale = +/- 2G & high resolution --> Sensitivity = 0.001G/digit.
+ address = LSM303_A_ADDR;
+ tx[0] = LSM303_A_CTRL_REG1;
+ tx[1] = 0x57; // --> 200 Hz Data rate speed - p.24/42 of datasheet
+ ack |= _i2c.write(address, tx, 2);
+ ack |= _i2c.write(address, tx, 1);
+ ack |= _i2c.read(address+1, &rx, 1); if (rx != 0x57) ack |= 1;
+ tx[0] = LSM303_A_CTRL_REG4;
+ tx[1] = 0x08; // 0000 1000 enable high resolution mode + selects default 2G scale. p.26/42
+ ack |= _i2c.write(address, tx ,2);
+ ack |= _i2c.write(address, tx, 1);
+ ack |= _i2c.read(address+1, &rx, 1); if (rx != 0x08) ack |= 1;
+//
+// 1.c enable LSM303 magnetometer and set operational mode:
+// CRA_REG is reset from 0x10 to 0x14 = 00010100 --> 30 Hz data output rate.
+// CRA_REG is reset from 0x10 to 0x18 = 00011000 --> 75 Hz data output rate.
+// CRA_REG is reset from 0x10 to 0x1C = 00011100 --> 220 Hz data output rate.
+// CRB_REG is kept at default = 00100000 = 0x20 --> range +/- 1.3 Gauss, Gain = 1100/980(Z) LSB/Gauss.
+// MR_REG is reset from 0x03 to 0x00 -> continuos conversion mode in stead of sleep mode.
+ address = LSM303_M_ADDR;
+ tx[0] = LSM303_M_CRA_REG;
+ tx[1] = 0x18; // --> 75 Hz minimum output rate - p.36/42 of datasheet
+ ack |= _i2c.write(address, tx, 2);
+ ack |= _i2c.write(address, tx, 1);
+ ack |= _i2c.read(address+1, &rx, 1); if (rx != 0x18) ack |= 1;
+ tx[0] = LSM303_M_MR_REG;
+ tx[1] = 0x00; // 0000 0000 --> continuous-conversion mode 25 Hz Data rate speed - p.24/42 of datasheet
+ ack |= _i2c.write(address, tx, 2);
+ ack |= _i2c.write(address, tx, 1);
+ ack |= _i2c.read(address+1, &rx, 1); if (rx != 0x00) ack |= 1;
+
+// 2. Initialize calibration constants with predetermined values.
+// acceleration:
+// My calibration values, vs. the website http://rwsarduino.blogspot.be/2013/01/inertial-orientation-sensing.html
+
+/* my predetermined static bias counts */
+ L3GD20_biasX = (int16_t) 90; /* digit counts */
+ L3GD20_biasY = (int16_t) -182;
+ L3GD20_biasZ = (int16_t) -10;
+
+/* reference gravity acceleration */
+ g_0 = 9.815;
+
+/* filter parameters: assume 50 Hz sampling rare and 2nd orcer Butterworth filter with fc = 6Hz. */
+ pi = 3.1415926536;
+ A = tan(pi*6/50); a = 1 + sqrt(2.0)*A + A*A;
+ FF[1] = 2*(A*A-1)/a;
+ FF[2] = (1-sqrt(2.0)*A+A*A)/a;
+ FF[0] = (1+FF[1]+FF[2])/4;
+
+ return ack;
+}
+
+char IMU::readData(float *d)
+{
+ char ack, reg, D[6];
+ int16_t W[3];
+
+// report the data in rad/s
+// gyro data are 16 bit readings per axis, stored: X_l, X_h, Y_l, Y_h, Z_l, Z_h
+// #define L3GD20_SENSITIVITY_250DPS 0.00875 --- #define L3GD20_DPS_TO_RADS 0.017453293
+ address = L3GD20_ADDR;
+ reg = L3GD20_OUT_X_L | 0x80; // set address auto-increment bit
+ ack = _i2c.write(address,®,1); ack |= _i2c.read(address+1,D,6);
+ W[0] = (int16_t) (D[1] << 8 | D[0]);
+ W[1] = (int16_t) (D[3] << 8 | D[2]);
+ W[2] = (int16_t) (D[5] << 8 | D[4]);
+ *(d+0) = (float) 0.971*(W[0]-L3GD20_biasX)*L3GD20_SENSITIVITY_250DPS*L3GD20_DPS_TO_RADS;
+ *(d+1) = (float) 0.998*(W[1]-L3GD20_biasY)*L3GD20_SENSITIVITY_250DPS*L3GD20_DPS_TO_RADS;
+ *(d+2) = (float) 1.002*(W[2]-L3GD20_biasZ)*L3GD20_SENSITIVITY_250DPS*L3GD20_DPS_TO_RADS;
+
+// Accelerometer data are stored as 12 bit readings, left justified per axis.
+// The data needs to be shifted 4 digits to the right! This is not general, only for the A measurement.
+ address = LSM303_A_ADDR;
+ reg = LSM303_A_OUT_X_L | 0x80; // set address auto-increment bit
+ ack |= _i2c.write(address,®,1); ack |= _i2c.read(address+1,D,6);
+ W[0] = ((int16_t) (D[1] << 8 | D[0])) >> 4;
+ W[1] = ((int16_t) (D[3] << 8 | D[2])) >> 4;
+ W[2] = ((int16_t) (D[5] << 8 | D[4])) >> 4;
+ *(d+3) = (float) g_0*0.991*(W[0]+34)/1000;
+ *(d+4) = (float) g_0*0.970*(W[1]+2)/1000;
+ *(d+5) = (float) g_0*0.983*(W[2]+28)/1000;
+// GN = 001
+// Magnetometer; are stored as 12 bit readings, right justified per axis.
+ address = LSM303_M_ADDR;
+ reg = LSM303_M_OUT_X_H | 0x80; // set address auto-increment bit
+ ack |= _i2c.write(address,®,1); ack |= _i2c.read(address+1,D,6);
+ W[0] = ((int16_t) (D[0] << 8 | D[1]));
+ W[1] = ((int16_t) (D[4] << 8 | D[5]));
+ W[2] = ((int16_t) (D[2] << 8 | D[3]));
+ *(d+6) = (float) 2.813*(W[0]-264)/1100;
+ *(d+7) = (float) 2.822*(W[1]- 98)/1100;
+ *(d+8) = (float) 2.880*(W[2]-305)/980;
+
+ return ack;
+}
+
+void IMU::filterData(float *d, double *D)
+// 2nd order Butterworth filter. Filter coefficients FF computed in function init.
+{
+ for (int i=0; i<9; ++i) {
+// *(FD+9*i+2) = *(FD+9*i+1); *(FD+9*i+1) = *(FD+9*i); *(FD+9*i) = (double) d[i];
+ FD[2][i] = FD[1][i]; FD[1][i] = FD[0][i]; FD[0][i] = (double) d[i];
+ FD[5][i] = FD[4][i]; FD[4][i] = FD[3][i];
+ FD[3][i] = FF[0]*(FD[0][i] + 2*FD[1][i] + FD[2][i]) - FF[1]*FD[4][i] - FF[2]*FD[5][i];
+ D[i] = FD[3][i];
+ }
+// D[0] = FD[0][2]; D[1] = FD[1][2]; D[2] = FD[2][2];
+}