root / trunk / code / lib / src / libdragonfly / rangefinder.c @ 277
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1 | 276 | emarinel | /**
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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 and Greg Tress
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38 | |||
39 | Last Modified: 4/30/06 by James
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40 | -Started log_distance conversion function !!!NOT COMPLETE!!!
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41 | -Cleaning up comments
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42 | |||
43 | -----------------
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44 | rangefinder.c
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45 | Using Sharp GP2D02 IR Rangefinder
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46 | |||
47 | Vin is the input to the rangefinder, designated RANGE_CTRL.
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48 | Vout is the output from the rangefinder, designated RANGE_IN# where # is the rangefinder you are reading from
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49 | |||
50 | Expected Initial Conditions:
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51 | Vin is high and Vout should read high.
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52 | |||
53 | Usage:
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54 | 1.) Set Vin low. Vout should read low.
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55 | 2.) Wait for high on Vout.
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56 | 3.) Begin clocking Vin and reading 8 bits from Vout (MSB first).
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57 | 4.) Set Vin high for 2ms or more to turn off rangefinder
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58 | |||
59 | */
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60 | |||
61 | #include "dragonfly_lib.h" |
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62 | #include "rangefinder.h" |
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63 | |||
64 | /*
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65 | read_distance returns the 8-bit reading from the rangefinder
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66 | parameters:
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67 | range_id - dio pin set as the rangefinder Vout [i.e. RANGE_IN0]
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68 | |||
69 | NOTE:
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70 | The Sharp GD2D02 returns values on a decreasing logrithmic scale.
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71 | So higher values correspond to closer distances. Use linearize_distance to convert to normal centimeter scale. Also, when reading distances closer than 8cm, the Sharp GD2D02 will return lower values than the values at 8cm.
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72 | At this point, we are only reading from one rangefinder [RANGE_IN0].
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73 | */
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74 | |||
75 | // constants
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76 | /* Nasty IR approximation table
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77 | I'm using this for the heck of it. We can do whatever.
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78 | |||
79 | Note the minimum value is .4V (20), and the maximum is 2.6V (133).
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80 | Gives distance in mm.
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81 | |||
82 | excel formula(valid for inputs 20-133): ROUND(2353.6*(E2^(-1.1146))*10,0)
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83 | |||
84 | This is only valid for the GP2D12, with objects directly ahead and more than
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85 | 10cm from the detector. See the datasheet for more information.
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86 | */
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87 | |||
88 | #define MIN_IR_ADC8 20 |
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89 | #define MAX_IR_ADC8 133 |
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90 | |||
91 | static int IR_dist_conversion[114] = { |
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92 | 800,791,751,714,681,651,623,597,574,552,531,512,494,478,462,447 |
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93 | ,434,421,408,397,386,375,365,356,347,338,330,322,315,307,301,294 |
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94 | ,288,282,276,270,265,260,255,250,245,241,237,232,228,224,221,217 |
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95 | ,213,210,207,203,200,197,194,191,189,186,183,181,178,176,173,171 |
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96 | ,169,166,164,162,160,158,156,154,152,151,149,147,145,144,142,140 |
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97 | ,139,137,136,134,133,131,130,129,127,126,125,124,122,121,120,119 |
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98 | ,118,117,115,114,113,112,111,110,109,108,107,106,105,105,104,103 |
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99 | ,102,101 |
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100 | }; |
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101 | |||
102 | int linearize_distance(int value); |
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103 | |||
104 | /**
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105 | * @defgroup rangefinder Rangefinder
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106 | * @brief Functions for using the IR rangefinders
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107 | *
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108 | * Functions for using the IR rangefinders.
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109 | *
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110 | * @{
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111 | **/
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112 | |||
113 | /**
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114 | * Initializes the rangefinders. This must be called before
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115 | * range_read_distance.
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116 | *
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117 | * @see range_read_distance
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118 | **/
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119 | void range_init(void){ |
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120 | digital_output(_PIN_B4,0);
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121 | } |
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122 | |||
123 | /**
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124 | * Reads the distance measured by one of the rangefinders.
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125 | * This distance is in arbitrary units.
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126 | *
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127 | * @param range_id the rangefinder to use. This should be one
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128 | * of the constants IR1 - IR5.
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129 | *
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130 | * @return the distance measured by the rangefinder
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131 | *
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132 | * @see range_init
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133 | **/
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134 | int range_read_distance (int range_id) { |
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135 | return linearize_distance(analog8(range_id));
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136 | } |
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137 | |||
138 | /** @} **/ //end defgroup |
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139 | |||
140 | int linearize_distance(int value) |
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141 | { |
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142 | if(value < MIN_IR_ADC8)
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143 | { |
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144 | return -1; |
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145 | } |
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146 | else if(value > MAX_IR_ADC8) |
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147 | { |
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148 | return -1; |
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149 | } |
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150 | else
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151 | { |
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152 | return IR_dist_conversion[value - MIN_IR_ADC8];
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153 | } |
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154 | } |
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155 | |||
156 |