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inc/IRDistance.c

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+// IRDistance.c
+// Runs on any microcontroller
+// Provide mid-level functions that convert raw ADC
+// values from the GP2Y0A21YK0F infrared distance sensors to
+// distances in mm. STUDENTS WILL NEED TO CALIBRATE THEIR OWN SENSORS
+// Jonathan Valvano
+// Jan 15, 2020
+
+/* This example accompanies the book
+   "Embedded Systems: Introduction to Robotics,
+   Jonathan W. Valvano, ISBN: 9781074544300, copyright (c) 2020
+ For more information about my classes, my research, and my books, see
+ http://users.ece.utexas.edu/~valvano/
+
+Simplified BSD License (FreeBSD License)
+Copyright (c) 2020, Jonathan Valvano, All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice,
+   this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+The views and conclusions contained in the software and documentation are
+those of the authors and should not be interpreted as representing official
+policies, either expressed or implied, of the FreeBSD Project.
+*/
+
+
+
+#include <stdint.h>
+
+/* Calibration data
+distance measured from front of the sensor to the wall                
+d(cm) 1/d    bL     al     aR   bR  adcSample d (0.01cm)  error
+10    0.100  2813  2830  2820  2830  2823.25  1006        0.06
+15    0.067  1935  1976  1986  1978  1968.75  1482       -0.18
+20    0.050  1520  1500  1520  1550  1522.5   1966       -0.34
+30    0.033  1040  1096  1028   933  1024.25  3099        0.99
+  
+      adcSample = 26813/d+159      2681300    
+      d = 26813/(adcSample-159)      -159    
+*/
+const int32_t A[4] = { 268130,268130,268130,268130};
+const int32_t B[4] = { -159,-159,-159,-159};
+const int32_t C[4] = { 0,0,0,0};
+const int32_t IRmax[4] = { 494,494,494,494};
+// returns distance in mm
+int32_t IRDistance_Convert(int32_t adcSample, uint32_t sensor){        
+  if(adcSample < IRmax[sensor]){
+    return 800;
+  }
+  return A[sensor]/(adcSample + B[sensor]) + C[sensor];
+}
+
+
+