Interface library for STMicro LSM303DLH 3-axis magnetometer w/ 3-axis acceleromter. Computes magnetic heading.
LSM303DLH.cpp
00001 /** LSM303DLH Interface Library 00002 * 00003 * Michael Shimniok http://bot-thoughts.com 00004 * 00005 * Based on test program by @tosihisa and 00006 * 00007 * Pololu sample library for LSM303DLH breakout by ryantm: 00008 * 00009 * Copyright (c) 2011 Pololu Corporation. For more information, see 00010 * 00011 * http://www.pololu.com/ 00012 * http://forum.pololu.com/ 00013 * 00014 * Permission is hereby granted, free of charge, to any person 00015 * obtaining a copy of this software and associated documentation 00016 * files (the "Software"), to deal in the Software without 00017 * restriction, including without limitation the rights to use, 00018 * copy, modify, merge, publish, distribute, sublicense, and/or sell 00019 * copies of the Software, and to permit persons to whom the 00020 * Software is furnished to do so, subject to the following 00021 * conditions: 00022 * 00023 * The above copyright notice and this permission notice shall be 00024 * included in all copies or substantial portions of the Software. 00025 * 00026 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 00027 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 00028 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 00029 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 00030 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 00031 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 00032 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 00033 * OTHER DEALINGS IN THE SOFTWARE. 00034 */ 00035 #include "mbed.h" 00036 #include "LSM303DLH.h" 00037 00038 #ifndef M_PI 00039 #define M_PI 3.14159265358979323846 00040 #endif 00041 00042 #define FILTER_SHIFT 6 // used in filtering acceleromter readings 00043 00044 const int addr_acc = 0x30; 00045 const int addr_mag = 0x3c; 00046 00047 enum REG_ADDRS { 00048 /* --- Mag --- */ 00049 CRA_REG_M = 0x00, 00050 CRB_REG_M = 0x01, 00051 MR_REG_M = 0x02, 00052 OUT_X_M = 0x03, 00053 OUT_Y_M = 0x05, 00054 OUT_Z_M = 0x07, 00055 /* --- Acc --- */ 00056 CTRL_REG1_A = 0x20, 00057 CTRL_REG4_A = 0x23, 00058 OUT_X_A = 0x28, 00059 OUT_Y_A = 0x2A, 00060 OUT_Z_A = 0x2C, 00061 }; 00062 00063 bool LSM303DLH::write_reg(int addr_i2c,int addr_reg, char v) 00064 { 00065 char data[2] = {addr_reg, v}; 00066 return LSM303DLH::_compass.write(addr_i2c, data, 2) == 0; 00067 } 00068 00069 bool LSM303DLH::read_reg(int addr_i2c,int addr_reg, char *v) 00070 { 00071 char data = addr_reg; 00072 bool result = false; 00073 00074 __disable_irq(); 00075 if ((_compass.write(addr_i2c, &data, 1) == 0) && (_compass.read(addr_i2c, &data, 1) == 0)){ 00076 *v = data; 00077 result = true; 00078 } 00079 __enable_irq(); 00080 return result; 00081 } 00082 00083 bool LSM303DLH::read_reg_short(int addr_i2c,int addr_reg, short *v) 00084 { 00085 char *pv = (char *)v; 00086 bool result; 00087 00088 result = read_reg(addr_i2c,addr_reg+0,pv+1); 00089 result &= read_reg(addr_i2c,addr_reg+1,pv+0); 00090 00091 return result; 00092 } 00093 00094 LSM303DLH::LSM303DLH(PinName sda, PinName scl): 00095 _compass(sda, scl), _offset_x(0), _offset_y(0), _offset_z(0), _scale_x(0), _scale_y(0), _scale_z(0), _filt_ax(0), _filt_ay(0), _filt_az(6000) 00096 { 00097 char reg_v; 00098 _compass.frequency(100000); 00099 00100 reg_v = 0; 00101 reg_v |= 0x01 << 5; /* Normal mode */ 00102 reg_v |= 0x07; /* X/Y/Z axis enable. */ 00103 write_reg(addr_acc,CTRL_REG1_A,reg_v); 00104 reg_v = 0; 00105 read_reg(addr_acc,CTRL_REG1_A,®_v); 00106 00107 reg_v = 0; 00108 reg_v |= 0x01 << 6; /* 1: data MSB @ lower address */ 00109 reg_v |= 0x01 << 4; /* +/- 4g */ 00110 write_reg(addr_acc,CTRL_REG4_A,reg_v); 00111 00112 /* -- mag --- */ 00113 reg_v = 0; 00114 reg_v |= 0x04 << 2; /* Minimum data output rate = 15Hz */ 00115 write_reg(addr_mag,CRA_REG_M,reg_v); 00116 00117 reg_v = 0; 00118 //reg_v |= 0x01 << 5; /* +-1.3Gauss */ 00119 reg_v |= 0x07 << 5; /* +-8.1Gauss */ 00120 write_reg(addr_mag,CRB_REG_M,reg_v); 00121 00122 reg_v = 0; /* Continuous-conversion mode */ 00123 write_reg(addr_mag,MR_REG_M,reg_v); 00124 } 00125 00126 00127 void LSM303DLH::setOffset(float x, float y, float z) 00128 { 00129 _offset_x = x; 00130 _offset_y = y; 00131 _offset_z = z; 00132 } 00133 00134 void LSM303DLH::setScale(float x, float y, float z) 00135 { 00136 _scale_x = x; 00137 _scale_y = y; 00138 _scale_z = z; 00139 } 00140 00141 void LSM303DLH::read(vector &a, vector &m) 00142 { 00143 short a_x, a_y, a_z; 00144 short m_x, m_y, m_z; 00145 //Timer t; 00146 //int usec1, usec2; 00147 00148 //t.reset(); 00149 //t.start(); 00150 00151 //usec1 = t.read_us(); 00152 read_reg_short(addr_acc, OUT_X_A, &a_x); 00153 read_reg_short(addr_acc, OUT_Y_A, &a_y); 00154 read_reg_short(addr_acc, OUT_Z_A, &a_z); 00155 read_reg_short(addr_mag, OUT_X_M, &m_x); 00156 read_reg_short(addr_mag, OUT_Y_M, &m_y); 00157 read_reg_short(addr_mag, OUT_Z_M, &m_z); 00158 //usec2 = t.read_us(); 00159 00160 //if (debug) debug->printf("%d %d %d\n", usec1, usec2, usec2-usec1); 00161 00162 // Perform simple lowpass filtering 00163 // Intended to stabilize heading despite 00164 // device vibration such as on a UGV 00165 _filt_ax += a_x - (_filt_ax >> FILTER_SHIFT); 00166 _filt_ay += a_y - (_filt_ay >> FILTER_SHIFT); 00167 _filt_az += a_z - (_filt_az >> FILTER_SHIFT); 00168 00169 a.x = (float) (_filt_ax >> FILTER_SHIFT); 00170 a.y = (float) (_filt_ay >> FILTER_SHIFT); 00171 a.z = (float) (_filt_az >> FILTER_SHIFT); 00172 00173 // offset and scale 00174 m.x = (m_x + _offset_x) * _scale_x; 00175 m.y = (m_y + _offset_y) * _scale_y; 00176 m.z = (m_z + _offset_z) * _scale_z; 00177 } 00178 00179 00180 // Returns the number of degrees from the -Y axis that it 00181 // is pointing. 00182 float LSM303DLH::heading() 00183 { 00184 return heading((vector){0,-1,0}); 00185 } 00186 00187 float LSM303DLH::heading(vector from) 00188 { 00189 vector a, m; 00190 00191 this->read(a, m); 00192 00193 //////////////////////////////////////////////// 00194 // compute heading 00195 //////////////////////////////////////////////// 00196 00197 vector temp_a = a; 00198 // normalize 00199 vector_normalize(&temp_a); 00200 //vector_normalize(&m); 00201 00202 // compute E and N 00203 vector E; 00204 vector N; 00205 vector_cross(&m,&temp_a,&E); 00206 vector_normalize(&E); 00207 vector_cross(&temp_a,&E,&N); 00208 00209 // compute heading 00210 float heading = atan2(vector_dot(&E,&from), vector_dot(&N,&from)) * 180/M_PI; 00211 if (heading < 0) heading += 360; 00212 00213 return heading; 00214 } 00215 00216 void LSM303DLH::frequency(int hz) 00217 { 00218 _compass.frequency(hz); 00219 }
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