105 lines
4.2 KiB
C
105 lines
4.2 KiB
C
// IRDistance.c
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// Runs on any microcontroller
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// Provide mid-level functions that convert raw ADC
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// values from the GP2Y0A21YK0F infrared distance sensors to
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// distances in mm. STUDENTS WILL NEED TO CALIBRATE THEIR OWN SENSORS
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// Jonathan Valvano
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// Jan 15, 2020
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/* This example accompanies the book
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"Embedded Systems: Introduction to Robotics,
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Jonathan W. Valvano, ISBN: 9781074544300, copyright (c) 2020
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For more information about my classes, my research, and my books, see
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http://users.ece.utexas.edu/~valvano/
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Simplified BSD License (FreeBSD License)
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Copyright (c) 2020, Jonathan Valvano, All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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The views and conclusions contained in the software and documentation are
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those of the authors and should not be interpreted as representing official
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policies, either expressed or implied, of the FreeBSD Project.
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*/
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#include <stdint.h>
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/* Calibration data
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distance measured from front of the sensor to the wall
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d(cm) 1/d bL al aR bR adcSample d (0.01cm) error
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10 0.100 2813 2830 2820 2830 2823.25 1006 0.06
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15 0.067 1935 1976 1986 1978 1968.75 1482 -0.18
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20 0.050 1520 1500 1520 1550 1522.5 1966 -0.34
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30 0.033 1040 1096 1028 933 1024.25 3099 0.99
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adcSample = 26813/d+159 2681300
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d = 26813/(adcSample-159) -159
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*/
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const int32_t A[4] = { 268130,268130,268130,268130};
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const int32_t B[4] = { -159,-159,-159,-159};
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const int32_t C[4] = { 0,0,0,0};
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const int32_t IRmax[4] = { 494,494,494,494};
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// returns distance in mm
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int32_t IRDistance_Convert(int32_t adcSample, uint32_t sensor){
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if(adcSample < IRmax[sensor]){
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return 300;
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}
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return A[sensor]/(adcSample + B[sensor]) + C[sensor];
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}
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/* Calibrated constants from IR_Calib.xlsx (3-12 inch range, 4 pts each)
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d(mm) = A / (adc + B) + C
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Right (PA26, ADC0 ch1): A=52850, B=-1239, C=69, RMSE~18mm
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Left (PA22, ADC0 ch7): A=137932, B=-859, C=32, RMSE~10mm
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Right RMSE is high because 9in and 12in ADC readings (1529 vs 1476)
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are only 53 counts apart, compressing the far-range fit.
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Below the minimum calibrated ADC the sensor is beyond ~12in/305mm,
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so 305 is returned as the out-of-range sentinel. */
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#define IR_RIGHT_A 199877
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#define IR_RIGHT_B -666
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#define IR_RIGHT_C 4
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#define IR_RIGHT_MIN_ADC 1381 // ADC at ~12 inches
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#define IR_LEFT_A 186922
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#define IR_LEFT_B -691
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#define IR_LEFT_C 9
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#define IR_LEFT_MIN_ADC 1372 // ADC at ~12 inches
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// returns distance in mm for the right IR sensor (PA26, ADC0 ch1)
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int32_t IRDistance_Right(int32_t adcSample){
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if(adcSample < IR_RIGHT_MIN_ADC){
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return 305;
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}
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return IR_RIGHT_A / (adcSample + IR_RIGHT_B) + IR_RIGHT_C;
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}
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// returns distance in mm for the left IR sensor (PA22, ADC0 ch7)
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int32_t IRDistance_Left(int32_t adcSample){
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if(adcSample < IR_LEFT_MIN_ADC){
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return 305;
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}
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return IR_LEFT_A / (adcSample + IR_LEFT_B) + IR_LEFT_C;
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}
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