root / demos / hunter_prey / lib / src / libdragonfly / rangefinder.c @ 1828
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1 | 1828 | emullini | /**
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2 | * Copyright (c) 2007 Colony Project
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3 | *
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4 | * Permission is hereby granted, free of charge, to any person
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5 | * obtaining a copy of this software and associated documentation
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6 | * files (the "Software"), to deal in the Software without
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7 | * restriction, including without limitation the rights to use,
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8 | * copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 | * copies of the Software, and to permit persons to whom the
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10 | * Software is furnished to do so, subject to the following
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11 | * conditions:
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12 | *
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13 | * The above copyright notice and this permission notice shall be
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14 | * included in all copies or substantial portions of the Software.
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15 | *
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16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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17 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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18 | * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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19 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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20 | * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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21 | * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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22 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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23 | * OTHER DEALINGS IN THE SOFTWARE.
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24 | **/
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25 | |||
26 | |||
27 | /**
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28 | * @file rangefinder.c
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29 | * @brief Rangefinders
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30 | *
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31 | * Implementation of functions for rangefinder use.
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32 | *
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33 | * @author Colony Project, CMU Robotics Club
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34 | **/
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35 | |||
36 | /*
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37 | Authors: James Kong, Greg Tress, Emily Hart
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38 | |||
39 | Last Modified: 5/12/10 by Emily
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40 | - Added Butterworth filtering functions. As of right now, the filter should
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41 | only be used if you really know what you are doing. These functions were
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42 | designed to be used with a task scheduler, which is not currently complete.
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43 | This implementation uses the RTC and runs massive computations in the RTC
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44 | interrupt.
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45 | |||
46 | Modified: 4/30/06 by James
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47 | -Started log_distance conversion function !!!NOT COMPLETE!!!
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48 | -Cleaning up comments
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49 | |||
50 | -----------------
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51 | rangefinder.c
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52 | Using Sharp GP2D02 IR Rangefinder
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53 | |||
54 | Vin is the input to the rangefinder, designated RANGE_CTRL.
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55 | Vout is the output from the rangefinder, designated RANGE_IN# where # is the
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56 | rangefinder you are reading from
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57 | |||
58 | Expected Initial Conditions:
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59 | Vin is high and Vout should read high.
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60 | |||
61 | Usage:
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62 | 1.) Set Vin low. Vout should read low.
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63 | 2.) Wait for high on Vout.
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64 | 3.) Begin clocking Vin and reading 8 bits from Vout (MSB first).
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65 | 4.) Set Vin high for 2ms or more to turn off rangefinder
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66 | |||
67 | */
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68 | #include <avr/pgmspace.h> |
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69 | #include <avr/interrupt.h> |
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70 | |||
71 | #include "rangefinder.h" |
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72 | #include "analog.h" |
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73 | #include "dio.h" |
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74 | #include "time.h" |
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75 | |||
76 | /*
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77 | read_distance returns the 8-bit reading from the rangefinder
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78 | parameters:
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79 | range_id - dio pin set as the rangefinder Vout [i.e. RANGE_IN0]
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80 | |||
81 | NOTE:
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82 | The Sharp GD2D02 returns values on a decreasing logrithmic scale.
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83 | So higher values correspond to closer distances. Use linearize_distance to convert to normal centimeter scale.
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84 | Also, when reading distances closer than 8cm, the Sharp GD2D02 will return lower values than the values at 8cm.
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85 | At this point, we are only reading from one rangefinder [RANGE_IN0].
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86 | */
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87 | |||
88 | // constants
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89 | /* Nasty IR approximation table
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90 | I'm using this for the heck of it. We can do whatever.
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91 | |||
92 | Note the minimum value is .4V (20), and the maximum is 2.6V (133).
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93 | Gives distance in mm.
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94 | |||
95 | excel formula(valid for inputs 20-133): ROUND(2353.6*(E2^(-1.1146))*10,0)
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96 | |||
97 | This is only valid for the GP2D12, with objects directly ahead and more than
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98 | 10cm from the detector. See the datasheet for more information.
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99 | */
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100 | |||
101 | static int IR_dist_conversion[72] PROGMEM = { |
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102 | 327,315,303,291,281,271,262,253,245,238,231,224,218,212,206,200, |
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103 | 195,190,185,181,177,173,168,165,161,158,155,151,148,145,143,140, |
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104 | 137,134,132,130,127,125,123,121,119,117,115,114,111,110,108,106, |
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105 | 105,104,102,100,99,98,97,95,94,93,91,90,89,88,87,86,84,83,83,82, |
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106 | 81,80,79,78 |
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107 | }; |
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108 | |||
109 | /* 1 if the filter is enabled, else 0 */
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110 | static int use_filter; |
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111 | // VALUE - MIN_IR_LINEAR is stored so only 8 bits are needed
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112 | /* X values for the Butterworth filter, for each rangefinder */
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113 | static uint8_t butter_x[5][4]; |
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114 | /* Y values for the Butterworth filter, for each rangefinder */
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115 | static uint8_t butter_y[5][3]; |
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116 | /* How many consecutive -1s have been seen by each rangefinder */
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117 | static uint8_t neg_one_count[5]; |
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118 | |||
119 | /**
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120 | * @defgroup rangefinder Rangefinder
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121 | * @brief Functions for using the IR rangefinders
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122 | *
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123 | * Functions for using the IR rangefinders.
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124 | *
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125 | * @{
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126 | **/
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127 | |||
128 | /**
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129 | * Initializes the rangefinders. This must be called before
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130 | * range_read_distance. This function does not initialize the filter.
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131 | *
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132 | * @see range_read_distance
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133 | **/
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134 | void range_init(void) |
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135 | { |
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136 | digital_output(_PIN_B4,0);
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137 | use_filter = 0;
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138 | } |
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139 | |||
140 | /**
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141 | * Initializes the rangefinders with an option to enable the Butterworth
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142 | * filtering.
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143 | *
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144 | * As of 5/12/2010, the filter should only be used if you really know what you
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145 | * are doing. It was designed to be used with a task scheduler, which is not
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146 | * currently complete. This implementation uses the RTC and runs massive
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147 | * computations in the RTC interrupt.
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148 | *
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149 | * @param filter 1 to enable the filter, 0 to leave it turned off
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150 | **/
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151 | void range_init_filter(int filter) |
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152 | { |
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153 | range_init(); |
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154 | if(filter){
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155 | use_filter = 1;
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156 | butter_init(); |
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157 | } |
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158 | } |
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159 | |||
160 | /**
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161 | * Reads the distance measured by one of the rangefinders.
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162 | * This distance is in arbitrary units.
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163 | *
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164 | * @param range_id the rangefinder to use. This should be one
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165 | * of the constants IR1 - IR5.
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166 | *
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167 | * @return the distance measured by the rangefinder
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168 | *
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169 | * @see range_init
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170 | **/
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171 | int range_read_distance(int range_id) { |
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172 | return linearize_distance(analog8(range_id));
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173 | } |
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174 | |||
175 | /**
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176 | * Transforms distance readings from logarithmic to linear scale.
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177 | * This probably isn't the function you are looking for.
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178 | *
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179 | * Note: pgm_read_word() needs additional testing
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180 | *
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181 | * @param value the 8-bit analog value from rangefinder
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182 | *
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183 | * @return linearized distance reading from rangefinder (integer in [101,800])
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184 | **/
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185 | int linearize_distance(int value) { |
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186 | if(value < MIN_IR_ADC8) {
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187 | return -1; |
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188 | } else if(value > MAX_IR_ADC8) { |
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189 | return -1; |
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190 | } else {
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191 | return pgm_read_word(&(IR_dist_conversion[value - MIN_IR_ADC8]));
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192 | } |
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193 | } |
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194 | |||
195 | /**
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196 | * Initializes the butterworth filter.
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197 | **/
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198 | void butter_init(void) |
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199 | { |
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200 | int i;
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201 | // init -1 count to 3 for each rangefinder
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202 | // this will cause them to restart the filter
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203 | for(i=0; i<5; i++) |
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204 | { |
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205 | neg_one_count[i] = 3;
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206 | } |
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207 | |||
208 | // set up the rtc to run butter_task periodically
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209 | rtc_init(SIXTEENTH_SECOND, butter_task); |
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210 | } |
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211 | |||
212 | /*
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213 | * Reads each rangefinder and sends its value through the Butterworth filter.
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214 | * This task should be run frequently so that range_read_filtered_distance
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215 | * returns fresh values
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216 | */
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217 | void butter_task(void) |
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218 | { |
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219 | butter_filter(IR1, range_read_distance(IR1)); |
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220 | butter_filter(IR2, range_read_distance(IR2)); |
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221 | butter_filter(IR3, range_read_distance(IR3)); |
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222 | butter_filter(IR4, range_read_distance(IR4)); |
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223 | butter_filter(IR5, range_read_distance(IR5)); |
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224 | } |
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225 | |||
226 | /*
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227 | * Butterworth helper function that takes a rangefinder ID and turns it into
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228 | * an array index between 0 and 4.
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229 | */
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230 | int get_range_index(int range_id){ |
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231 | switch(range_id){
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232 | case IR1:
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233 | return 0; |
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234 | case IR2:
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235 | return 1; |
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236 | case IR3:
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237 | return 2; |
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238 | case IR4:
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239 | return 3; |
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240 | case IR5:
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241 | return 4; |
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242 | default: // should never happen |
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243 | return 0xff; |
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244 | } |
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245 | } |
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246 | |||
247 | /**
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248 | * Puts the given value from the given rangefinder through the Butterworth
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249 | * filter. This function should be called every time a new value is read from a
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250 | * rangefinder.
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251 | *
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252 | * The Butterworth filter has a cutoff frequency of 5Hz and an order of 3
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253 | *
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254 | * @param range_id the rangefinder to use. This should be one of the constants
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255 | * IR1 - IR5.
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256 | * @param the value read from that rangefinder
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257 | **/
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258 | void butter_filter(int range_id, int val) |
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259 | { |
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260 | int range_index = get_range_index(range_id);
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261 | // we have a non-error value
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262 | if(val > -1 && val <= MAX_IR_LINEAR) |
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263 | { |
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264 | // we just passed two or fewer -1's: act as though none seen
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265 | if(neg_one_count[range_index] < 3) |
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266 | { |
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267 | // shift the values of the arrays to the left
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268 | int i;
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269 | for(i=0; i<2; i++) |
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270 | { |
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271 | butter_x[range_index][i] = butter_x[range_index][i+1];
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272 | butter_y[range_index][i] = butter_y[range_index][i+1];
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273 | } |
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274 | butter_x[range_index][2] = butter_x[range_index][3]; |
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275 | // add the new value to the X array
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276 | butter_x[range_index][3] = val - MIN_IR_LINEAR;
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277 | } |
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278 | // we just passed three or more -1 values: reset filter with new value
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279 | else
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280 | { |
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281 | int i;
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282 | // fill x and y values with the new value
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283 | for(i=0; i<3; i++) |
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284 | { |
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285 | butter_x[range_index][i] = val - MIN_IR_LINEAR; |
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286 | butter_y[range_index][i] = val - MIN_IR_LINEAR; |
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287 | } |
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288 | butter_x[range_index][3] = val - MIN_IR_LINEAR;
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289 | } |
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290 | |||
291 | // reset the -1 count value
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292 | neg_one_count[range_index] = 0;
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293 | |||
294 | /*
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295 | * butterworth filter the last values
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296 | *
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297 | * butterworth filter equation is
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298 | * y(t) = x(t-3)/6 + x(t-2)/2 + x(t-1)/2 + x(t)/6 - y(t-2)/3
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299 | *
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300 | * values are multiplied by 16 before divisions, and divided by 16 at the
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301 | * very end to mitigate rounding errors
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302 | *
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303 | * 8 is added before dividing by 16 so that numbers are rounded instead of
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304 | * truncated
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305 | */
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306 | int16_t temp1 = (int16_t)butter_x[range_index][3] +
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307 | (int16_t)butter_x[range_index][0] + (2*MIN_IR_LINEAR); |
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308 | int16_t temp2 = (int16_t)butter_x[range_index][2] +
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309 | (int16_t)butter_x[range_index][1] + (2*MIN_IR_LINEAR); |
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310 | int16_t temp3 = (int16_t)butter_y[range_index][0] + MIN_IR_LINEAR;
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311 | int16_t filtered_big = ((((temp1*8)-(temp3*16))/3)+(temp2*8)+8)/16; |
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312 | filtered_big -= MIN_IR_LINEAR; |
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313 | uint8_t filtered = filtered_big > 0xff ? 0xff : (uint8_t)filtered_big; |
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314 | |||
315 | butter_y[range_index][2] = filtered;
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316 | } |
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317 | // -1 seen - don't want to store it
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318 | else
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319 | { |
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320 | // increment -1 count, preventing overflow
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321 | neg_one_count[range_index] = neg_one_count[range_index] == 0xff ? 0xff : |
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322 | neg_one_count[range_index]+1;
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323 | } |
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324 | } |
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325 | |||
326 | /**
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327 | * Returns the most recent filtered reading of the rangefinder. The raw
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328 | * rangefinder values have been run through a Butterworth filter.
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329 | *
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330 | * If the filter was not initialized in rangefinder_init, will return the
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331 | * unfiltered value from the rangefinder.
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332 | *
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333 | * @param range_id the rangefinder to use. This should be one of the constants
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334 | * IR1 - IR5.
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335 | **/
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336 | int range_read_filtered_distance(int range_id){ |
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337 | if(!use_filter){
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338 | return range_read_distance(range_id);
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339 | } |
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340 | |||
341 | int range_index = get_range_index(range_id);
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342 | |||
343 | // haven't seen too many -1s recently - return filtered value
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344 | if(neg_one_count[range_index] < 3) |
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345 | { |
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346 | return butter_y[range_index][2] + MIN_IR_LINEAR; |
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347 | } |
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348 | // have seen several -1s - return -1
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349 | return -1; |
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350 | } |
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351 | |||
352 | /** @} **/ //end defgroup |