The IMUfilter Roll/Pitch/Yaw example wrapped up into a class for easier use with other programs: http://mbed.org/users/aberk/programs/IMUfilter_RPYExample/latest
Diff: IMU.cpp
- Revision:
- 0:51d01aa47c71
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/IMU.cpp Wed Aug 11 11:09:47 2010 +0000 @@ -0,0 +1,235 @@ +/** + * @section LICENSE + * + * Copyright (c) 2010 ARM Limited + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + * + * @section DESCRIPTION + * + * IMU consisting of ADXL345 accelerometer and ITG-3200 gyroscope using + * orientation filter developed by Sebastian Madgwick. + * + * Find more details about his paper here: + * + * http://code.google.com/p/imumargalgorithm30042010sohm/ + */ + + +/** + * Includes + */ +#include "IMU.h" + +IMU::IMU(float imuRate, + double gyroscopeMeasurementError, + float accelerometerRate, + float gyroscopeRate) : accelerometer(p5, p6, p7, p8), + gyroscope(p9, p10), imuFilter(imuRate, gyroscopeMeasurementError) { + + imuRate_ = imuRate; + accelerometerRate_ = accelerometerRate; + gyroscopeRate_ = gyroscopeRate; + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + + accelerometerSamples = 0; + gyroscopeSamples = 0; + + initializeAccelerometer(); + calibrateAccelerometer(); + + initializeGyroscope(); + calibrateGyroscope(); + + accelerometerTicker.attach(this, &IMU::sampleAccelerometer, accelerometerRate_); + gyroscopeTicker.attach(this, &IMU::sampleGyroscope, gyroscopeRate_); + filterTicker.attach(this, &IMU::filter, imuRate_); + +} + +double IMU::getRoll(void) { + + return toDegrees(imuFilter.getRoll()); + +} + +double IMU::getPitch(void) { + + return toDegrees(imuFilter.getPitch()); + +} + +double IMU::getYaw(void) { + + return toDegrees(imuFilter.getYaw()); + +} + +void IMU::initializeAccelerometer(void) { + + //Go into standby mode to configure the device. + accelerometer.setPowerControl(0x00); + //Full resolution, +/-16g, 4mg/LSB. + accelerometer.setDataFormatControl(0x0B); + //200Hz data rate. + accelerometer.setDataRate(ADXL345_200HZ); + //Measurement mode. + accelerometer.setPowerControl(0x08); + //See http://www.analog.com/static/imported-files/application_notes/AN-1077.pdf + wait_ms(22); + +} + +void IMU::sampleAccelerometer(void) { + + if (accelerometerSamples == SAMPLES) { + + a_x = ((a_xAccumulator / SAMPLES) - a_xBias) * ACCELEROMETER_GAIN; + a_y = ((a_yAccumulator / SAMPLES) - a_yBias) * ACCELEROMETER_GAIN; + a_z = ((a_zAccumulator / SAMPLES) - a_zBias) * ACCELEROMETER_GAIN; + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + accelerometerSamples = 0; + + } else { + + accelerometer.getOutput(readings); + + a_xAccumulator += (int16_t) readings[0]; + a_yAccumulator += (int16_t) readings[1]; + a_zAccumulator += (int16_t) readings[2]; + + accelerometerSamples++; + + } + +} + +void IMU::calibrateAccelerometer(void) { + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + + for (int i = 0; i < CALIBRATION_SAMPLES; i++) { + + accelerometer.getOutput(readings); + + a_xAccumulator += (int16_t) readings[0]; + a_yAccumulator += (int16_t) readings[1]; + a_zAccumulator += (int16_t) readings[2]; + + wait(accelerometerRate_); + + } + + a_xAccumulator /= CALIBRATION_SAMPLES; + a_yAccumulator /= CALIBRATION_SAMPLES; + a_zAccumulator /= CALIBRATION_SAMPLES; + + a_xBias = a_xAccumulator; + a_yBias = a_yAccumulator; + a_zBias = (a_zAccumulator - 250); + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + +} + +void IMU::initializeGyroscope(void) { + + //Low pass filter bandwidth of 42Hz. + gyroscope.setLpBandwidth(LPFBW_42HZ); + //Internal sample rate of 200Hz. + gyroscope.setSampleRateDivider(4); + +} + +void IMU::calibrateGyroscope(void) { + + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + + for (int i = 0; i < CALIBRATION_SAMPLES; i++) { + + w_xAccumulator += gyroscope.getGyroX(); + w_yAccumulator += gyroscope.getGyroY(); + w_zAccumulator += gyroscope.getGyroZ(); + wait(gyroscopeRate_); + + } + + //Average the samples. + w_xAccumulator /= CALIBRATION_SAMPLES; + w_yAccumulator /= CALIBRATION_SAMPLES; + w_zAccumulator /= CALIBRATION_SAMPLES; + + w_xBias = w_xAccumulator; + w_yBias = w_yAccumulator; + w_zBias = w_zAccumulator; + + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + +} + +void IMU::sampleGyroscope(void) { + + if (gyroscopeSamples == SAMPLES) { + + w_x = toRadians(((w_xAccumulator / SAMPLES) - w_xBias) * GYROSCOPE_GAIN); + w_y = toRadians(((w_yAccumulator / SAMPLES) - w_yBias) * GYROSCOPE_GAIN); + w_z = toRadians(((w_zAccumulator / SAMPLES) - w_zBias) * GYROSCOPE_GAIN); + + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + gyroscopeSamples = 0; + + } else { + + w_xAccumulator += gyroscope.getGyroX(); + w_yAccumulator += gyroscope.getGyroY(); + w_zAccumulator += gyroscope.getGyroZ(); + + gyroscopeSamples++; + + } + +} + +void IMU::filter(void) { + + //Update the filter variables. + imuFilter.updateFilter(w_y, w_x, w_z, a_y, a_x, a_z); + //Calculate the new Euler angles. + imuFilter.computeEuler(); + +}