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--- a/RTOS_Labs_common/IRDistance.c
+++ b/RTOS_Labs_common/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 300;
+  }
+  return A[sensor]/(adcSample + B[sensor]) + C[sensor];
+}
+
+/* Calibrated constants from IR_Calib.xlsx (3-12 inch range, 4 pts each)
+   d(mm) = A / (adc + B) + C
+   Right (PA26, ADC0 ch1): A=52850,  B=-1239, C=69,  RMSE~18mm
+   Left  (PA22, ADC0 ch7): A=137932, B=-859,  C=32,  RMSE~10mm
+   Right RMSE is high because 9in and 12in ADC readings (1529 vs 1476)
+   are only 53 counts apart, compressing the far-range fit.
+   Below the minimum calibrated ADC the sensor is beyond ~12in/305mm,
+   so 305 is returned as the out-of-range sentinel. */
+#define IR_RIGHT_A       199877
+#define IR_RIGHT_B       -666
+#define IR_RIGHT_C          4
+#define IR_RIGHT_MIN_ADC  1381   // ADC at ~12 inches
+
+#define IR_LEFT_A       186922
+#define IR_LEFT_B         -691
+#define IR_LEFT_C           9
+#define IR_LEFT_MIN_ADC   1372   // ADC at ~12 inches
+
+// returns distance in mm for the right IR sensor (PA26, ADC0 ch1)
+int32_t IRDistance_Right(int32_t adcSample){
+  if(adcSample < IR_RIGHT_MIN_ADC){
+    return 305;
+  }
+  return IR_RIGHT_A / (adcSample + IR_RIGHT_B) + IR_RIGHT_C;
+}
+
+// returns distance in mm for the left IR sensor (PA22, ADC0 ch7)
+int32_t IRDistance_Left(int32_t adcSample){
+  if(adcSample < IR_LEFT_MIN_ADC){
+    return 305;
+  }
+  return IR_LEFT_A / (adcSample + IR_LEFT_B) + IR_LEFT_C;
+}
+
+