root / branches / encoders / code / lib / src / libdragonfly / rangefinder.c @ 1345
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1 | 7 | bcoltin | /*
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2 | Authors: James Kong and Greg Tress
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3 | |||
4 | Last Modified: 4/30/06 by James
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5 | -Started log_distance conversion function !!!NOT COMPLETE!!!
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6 | -Cleaning up comments
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7 | |||
8 | -----------------
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9 | rangefinder.c
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10 | Using Sharp GP2D02 IR Rangefinder
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11 | |||
12 | Vin is the input to the rangefinder, designated RANGE_CTRL.
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13 | Vout is the output from the rangefinder, designated RANGE_IN# where # is the rangefinder you are reading from
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14 | |||
15 | Expected Initial Conditions:
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16 | Vin is high and Vout should read high.
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17 | |||
18 | Usage:
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19 | 1.) Set Vin low. Vout should read low.
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20 | 2.) Wait for high on Vout.
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21 | 3.) Begin clocking Vin and reading 8 bits from Vout (MSB first).
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22 | 4.) Set Vin high for 2ms or more to turn off rangefinder
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23 | |||
24 | */
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25 | |||
26 | #include "dragonfly_lib.h" |
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27 | #include "rangefinder.h" |
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28 | |||
29 | /*
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30 | read_distance returns the 8-bit reading from the rangefinder
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31 | parameters:
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32 | range_id - dio pin set as the rangefinder Vout [i.e. RANGE_IN0]
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33 | |||
34 | NOTE:
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35 | The Sharp GD2D02 returns values on a decreasing logrithmic scale.
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36 | So higher values correspond to closer distances. Use linearize_distance to convert to normal centimeter scale.
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37 | Also, when reading distances closer than 8cm, the Sharp GD2D02 will return lower values than the values at 8cm.
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38 | At this point, we are only reading from one rangefinder [RANGE_IN0].
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39 | */
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40 | |||
41 | // constants
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42 | /* Nasty IR approximation table
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43 | I'm using this for the heck of it. We can do whatever.
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44 | |||
45 | Note the minimum value is .4V (20), and the maximum is 2.6V (133).
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46 | Gives distance in mm.
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47 | |||
48 | excel formula(valid for inputs 20-133): ROUND(2353.6*(E2^(-1.1146))*10,0)
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49 | |||
50 | This is only valid for the GP2D12, with objects directly ahead and more than
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51 | 10cm from the detector. See the datasheet for more information.
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52 | */
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53 | |||
54 | #define MIN_IR_ADC8 20 |
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55 | #define MAX_IR_ADC8 133 |
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56 | |||
57 | static int IR_dist_conversion[114] = { |
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58 | 800,791,751,714,681,651,623,597,574,552,531,512,494,478,462,447 |
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59 | ,434,421,408,397,386,375,365,356,347,338,330,322,315,307,301,294 |
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60 | ,288,282,276,270,265,260,255,250,245,241,237,232,228,224,221,217 |
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61 | ,213,210,207,203,200,197,194,191,189,186,183,181,178,176,173,171 |
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62 | ,169,166,164,162,160,158,156,154,152,151,149,147,145,144,142,140 |
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63 | ,139,137,136,134,133,131,130,129,127,126,125,124,122,121,120,119 |
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64 | ,118,117,115,114,113,112,111,110,109,108,107,106,105,105,104,103 |
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65 | ,102,101 |
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66 | }; |
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67 | |||
68 | int linearize_distance(int value); |
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69 | |||
70 | /**
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71 | * @defgroup rangefinder Rangefinder
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72 | * @brief Functions for using the IR rangefinders
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73 | *
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74 | * Functions for using the IR rangefinders.
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75 | *
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76 | * @{
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77 | **/
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78 | |||
79 | /**
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80 | * Initializes the rangefinders. This must be called before
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81 | * range_read_distance.
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82 | *
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83 | * @see range_read_distance
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84 | **/
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85 | void range_init(void){ |
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86 | digital_output(_PIN_B4,0);
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87 | } |
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88 | |||
89 | /**
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90 | * Reads the distance measured by one of the rangefinders.
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91 | * This distance is in arbitrary units.
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92 | *
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93 | * @param range_id the rangefinder to use. This should be one
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94 | * of the constants IR1 - IR5.
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95 | *
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96 | * @return the distance measured by the rangefinder
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97 | *
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98 | * @see range_init
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99 | **/
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100 | int range_read_distance (int range_id) { |
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101 | return linearize_distance(analog8(range_id));
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102 | } |
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103 | |||
104 | /** @} **/ //end defgroup |
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105 | |||
106 | int linearize_distance(int value) |
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107 | { |
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108 | if(value < MIN_IR_ADC8)
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109 | { |
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110 | return -1; |
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111 | } |
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112 | else if(value > MAX_IR_ADC8) |
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113 | { |
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114 | return -1; |
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115 | } |
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116 | else
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117 | { |
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118 | return IR_dist_conversion[value - MIN_IR_ADC8];
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119 | } |
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120 | } |
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121 | |||
122 |