Arduino version , update and tested on NUCLEO-L073RZ

Dependencies:   mbed

Oximeter and pulse sensor, based on the Beer-Lambert gas absorption law

MAXREFDES117 ( MAX30102 ) from MAXIM, based on MAXIM library for Arduino

adaptation C.Dupaty 07-2017

Tested on STM32 NUCLEO-F411RE and NUCLEO-L073RZ

https://os.mbed.com/media/uploads/cdupaty/max30102.jpg

Revision:
4:5273ab1085ab
Parent:
3:7c0fb55eb3ff
--- a/algorithm/algorithm.cpp	Thu Apr 21 19:38:17 2016 +0000
+++ b/algorithm/algorithm.cpp	Thu May 19 22:04:06 2016 +0000
@@ -4,31 +4,28 @@
 * Filename: algorithm.cpp
 * Description: This module calculates the heart rate/SpO2 level
 *
-* Revision History:
-*\n 1-18-2016 Rev 01.00 SK Initial release.
-*\n
 *
 * --------------------------------------------------------------------
 *
 * This code follows the following naming conventions:
 *
-*\n char              ch_pmod_value
-*\n char (array)      s_pmod_s_string[16]
-*\n float             f_pmod_value
-*\n int32_t           n_pmod_value
-*\n int32_t (array)   an_pmod_value[16]
-*\n int16_t           w_pmod_value
-*\n int16_t (array)   aw_pmod_value[16]
-*\n uint16_t          uw_pmod_value
-*\n uint16_t (array)  auw_pmod_value[16]
-*\n uint8_t           uch_pmod_value
-*\n uint8_t (array)   auch_pmod_buffer[16]
-*\n uint32_t          un_pmod_value
-*\n int32_t *         pn_pmod_value
+* char              ch_pmod_value
+* char (array)      s_pmod_s_string[16]
+* float             f_pmod_value
+* int32_t           n_pmod_value
+* int32_t (array)   an_pmod_value[16]
+* int16_t           w_pmod_value
+* int16_t (array)   aw_pmod_value[16]
+* uint16_t          uw_pmod_value
+* uint16_t (array)  auw_pmod_value[16]
+* uint8_t           uch_pmod_value
+* uint8_t (array)   auch_pmod_buffer[16]
+* uint32_t          un_pmod_value
+* int32_t *         pn_pmod_value
 *
 * ------------------------------------------------------------------------- */
 /*******************************************************************************
-* Copyright (C) 2015 Maxim Integrated Products, Inc., All Rights Reserved.
+* Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
@@ -62,8 +59,8 @@
 #include "algorithm.h"
 #include "mbed.h"
 
-void maxim_heart_rate_and_oxygen_saturation(uint32_t *pun_ir_buffer ,  int32_t n_ir_buffer_length, uint32_t *pun_red_buffer ,   int32_t *pn_spo2, int8_t *pch_spo2_valid , 
-                              int32_t *pn_heart_rate , int8_t  *pch_hr_valid)
+void maxim_heart_rate_and_oxygen_saturation(uint32_t *pun_ir_buffer,  int32_t n_ir_buffer_length, uint32_t *pun_red_buffer, int32_t *pn_spo2, int8_t *pch_spo2_valid, 
+                              int32_t *pn_heart_rate, int8_t  *pch_hr_valid)
 /**
 * \brief        Calculate the heart rate and SpO2 level
 * \par          Details
@@ -82,191 +79,179 @@
 * \retval       None
 */
 {
-
+    uint32_t un_ir_mean ,un_only_once ;
+    int32_t k ,n_i_ratio_count;
+    int32_t i,s ,m, n_exact_ir_valley_locs_count ,n_middle_idx;
+    int32_t n_th1, n_npks,n_c_min;      
+    int32_t an_ir_valley_locs[15] ;
+    int32_t an_exact_ir_valley_locs[15] ;
+    int32_t an_dx_peak_locs[15] ;
+    int32_t n_peak_interval_sum;
+    
+    int32_t n_y_ac, n_x_ac;
+    int32_t n_spo2_calc; 
+    int32_t n_y_dc_max, n_x_dc_max; 
+    int32_t n_y_dc_max_idx, n_x_dc_max_idx; 
+    int32_t an_ratio[5],n_ratio_average; 
+    int32_t n_nume,  n_denom ;
+    // remove DC of ir signal    
+    un_ir_mean =0; 
+    for (k=0 ; k<n_ir_buffer_length ; k++ ) un_ir_mean += pun_ir_buffer[k] ;
+    un_ir_mean =un_ir_mean/n_ir_buffer_length ;
+    for (k=0 ; k<n_ir_buffer_length ; k++ )  an_x[k] =  pun_ir_buffer[k] - un_ir_mean ; 
+    
+    // 4 pt Moving Average
+    for(k=0; k< BUFFER_SIZE-MA4_SIZE; k++){
+        n_denom= ( an_x[k]+an_x[k+1]+ an_x[k+2]+ an_x[k+3]);
+        an_x[k]=  n_denom/(int32_t)4; 
+    }
 
-        uint32_t un_ir_mean ,un_only_once ;
-        int32_t k ,n_i_ratio_count;
-        int32_t i,s ,m, n_exact_ir_valley_locs_count ,n_middle_idx;
-        int32_t n_th1, n_npks,n_c_min;      
-        int32_t an_ir_valley_locs[15] ;
-        int32_t an_exact_ir_valley_locs[15] ;
-        int32_t an_dx_peak_locs[15] ;
-        int32_t n_peak_interval_sum;
-        
-        int32_t n_y_ac, n_x_ac;
-        int32_t n_spo2_calc; 
-        int32_t n_y_dc_max, n_x_dc_max; 
-        int32_t n_y_dc_max_idx, n_x_dc_max_idx; 
-        int32_t an_ratio[5],n_ratio_average; 
-        int32_t n_nume,  n_denom ;
-        // remove DC of ir signal    
-        un_ir_mean =0; 
-        for (k=0 ; k<n_ir_buffer_length ; k++ ) un_ir_mean += pun_ir_buffer[k] ;
-        un_ir_mean =un_ir_mean/n_ir_buffer_length ;
-        for (k=0 ; k<n_ir_buffer_length ; k++ )  an_x[k] =  pun_ir_buffer[k] - un_ir_mean ; 
-        
-        // 4 pt Moving Average
-        for(k=0; k< BUFFER_SIZE-MA4_SIZE; k++){
-          n_denom= ( an_x[k]+an_x[k+1]+ an_x[k+2]+ an_x[k+3]);
-          an_x[k]=  n_denom/(int32_t)4; 
-        }
-
-        // get difference of smoothed IR signal
-        
-       for( k=0; k<BUFFER_SIZE-MA4_SIZE-1;  k++)
-           an_dx[k]= (an_x[k+1]- an_x[k]);
+    // get difference of smoothed IR signal
+    
+    for( k=0; k<BUFFER_SIZE-MA4_SIZE-1;  k++)
+        an_dx[k]= (an_x[k+1]- an_x[k]);
 
-       // 2-pt Moving Average to an_dx
-       for(k=0; k< BUFFER_SIZE-MA4_SIZE-2; k++){
-          an_dx[k] =  ( an_dx[k]+an_dx[k+1])/2 ;
-        }
-        
-       // hamming window
-       // flip wave form so that we can detect valley with peak detector
-        for ( i=0 ; i<BUFFER_SIZE-HAMMING_SIZE-MA4_SIZE-2 ;i++){
-            s= 0;
-            for( k=i; k<i+ HAMMING_SIZE ;k++){
-                s -= an_dx[k] *auw_hamm[k-i] ; 
-                         }
-            an_dx[i]= s/ (int32_t)1146; // divide by sum of auw_hamm 
-        }
+    // 2-pt Moving Average to an_dx
+    for(k=0; k< BUFFER_SIZE-MA4_SIZE-2; k++){
+        an_dx[k] =  ( an_dx[k]+an_dx[k+1])/2 ;
+    }
     
-     
-        n_th1=0; // threshold calculation
-        for ( k=0 ; k<BUFFER_SIZE-HAMMING_SIZE ;k++){
-                n_th1 += ((an_dx[k]>0)? an_dx[k] : ((int32_t)0-an_dx[k])) ;
-        }
-        n_th1= n_th1/ ( BUFFER_SIZE-HAMMING_SIZE);
-        // peak location is acutally index for sharpest location of raw signal since we flipped the signal         
-        maxim_find_peaks( an_dx_peak_locs, &n_npks, an_dx, BUFFER_SIZE-HAMMING_SIZE, n_th1, 8, 5 );//peak_height, peak_distance, max_num_peaks 
+    // hamming window
+    // flip wave form so that we can detect valley with peak detector
+    for ( i=0 ; i<BUFFER_SIZE-HAMMING_SIZE-MA4_SIZE-2 ;i++){
+        s= 0;
+        for( k=i; k<i+ HAMMING_SIZE ;k++){
+            s -= an_dx[k] *auw_hamm[k-i] ; 
+                     }
+        an_dx[i]= s/ (int32_t)1146; // divide by sum of auw_hamm 
+    }
 
-        n_peak_interval_sum =0;
-                if (n_npks>=2){
-                      for (k=1; k<n_npks; k++)
-                             n_peak_interval_sum += (an_dx_peak_locs[k] -an_dx_peak_locs[k -1] ) ;
-                      n_peak_interval_sum =n_peak_interval_sum/(n_npks-1);
-                     *pn_heart_rate =(int32_t)( 6000/ n_peak_interval_sum );// beats per minutes
-                      //prlongf(">>>  *pn_heart_rate= %d \n", *pn_heart_rate) ;
-                      *pch_hr_valid  = 1;
-                }
-                else  {
-                      *pn_heart_rate = -999;
-                      *pch_hr_valid  = 0;
-                }
-                
-        for ( k=0 ; k<n_npks ;k++)
-            an_ir_valley_locs[k]= an_dx_peak_locs[k] +HAMMING_SIZE /2; 
+ 
+    n_th1=0; // threshold calculation
+    for ( k=0 ; k<BUFFER_SIZE-HAMMING_SIZE ;k++){
+        n_th1 += ((an_dx[k]>0)? an_dx[k] : ((int32_t)0-an_dx[k])) ;
+    }
+    n_th1= n_th1/ ( BUFFER_SIZE-HAMMING_SIZE);
+    // peak location is acutally index for sharpest location of raw signal since we flipped the signal         
+    maxim_find_peaks( an_dx_peak_locs, &n_npks, an_dx, BUFFER_SIZE-HAMMING_SIZE, n_th1, 8, 5 );//peak_height, peak_distance, max_num_peaks 
+
+    n_peak_interval_sum =0;
+    if (n_npks>=2){
+        for (k=1; k<n_npks; k++)
+            n_peak_interval_sum += (an_dx_peak_locs[k]-an_dx_peak_locs[k -1]);
+        n_peak_interval_sum=n_peak_interval_sum/(n_npks-1);
+        *pn_heart_rate=(int32_t)(6000/n_peak_interval_sum);// beats per minutes
+        *pch_hr_valid  = 1;
+    }
+    else  {
+        *pn_heart_rate = -999;
+        *pch_hr_valid  = 0;
+    }
+            
+    for ( k=0 ; k<n_npks ;k++)
+        an_ir_valley_locs[k]=an_dx_peak_locs[k]+HAMMING_SIZE/2; 
 
 
-          // raw value : RED(=y) and IR(=X)
-          // we need to assess DC and AC value of ir and red PPG. 
-            for (k=0 ; k<n_ir_buffer_length ; k++ )  {
-                an_x[k] =  pun_ir_buffer[k] ; 
-                an_y[k] =  pun_red_buffer[k] ; 
-            }
+    // raw value : RED(=y) and IR(=X)
+    // we need to assess DC and AC value of ir and red PPG. 
+    for (k=0 ; k<n_ir_buffer_length ; k++ )  {
+        an_x[k] =  pun_ir_buffer[k] ; 
+        an_y[k] =  pun_red_buffer[k] ; 
+    }
+
+    // find precise min near an_ir_valley_locs
+    n_exact_ir_valley_locs_count =0; 
+    for(k=0 ; k<n_npks ;k++){
+        un_only_once =1;
+        m=an_ir_valley_locs[k];
+        n_c_min= 16777216;//2^24;
+        if (m+5 <  BUFFER_SIZE-HAMMING_SIZE  && m-5 >0){
+            for(i= m-5;i<m+5; i++)
+                if (an_x[i]<n_c_min){
+                    if (un_only_once >0){
+                       un_only_once =0;
+                   } 
+                   n_c_min= an_x[i] ;
+                   an_exact_ir_valley_locs[k]=i;
+                }
+            if (un_only_once ==0)
+                n_exact_ir_valley_locs_count ++ ;
+        }
+    }
+    if (n_exact_ir_valley_locs_count <2 ){
+       *pn_spo2 =  -999 ; // do not use SPO2 since signal ratio is out of range
+       *pch_spo2_valid  = 0; 
+       return;
+    }
+    // 4 pt MA
+    for(k=0; k< BUFFER_SIZE-MA4_SIZE; k++){
+        an_x[k]=( an_x[k]+an_x[k+1]+ an_x[k+2]+ an_x[k+3])/(int32_t)4;
+        an_y[k]=( an_y[k]+an_y[k+1]+ an_y[k+2]+ an_y[k+3])/(int32_t)4;
+    }
 
-        // find precise min near an_ir_valley_locs
-        n_exact_ir_valley_locs_count =0; 
-        for ( k=0 ; k<n_npks ;k++){
-            un_only_once =1;
-            m=an_ir_valley_locs[k];
-            n_c_min= 16777216;//2^24;
-            if (m+5 <  BUFFER_SIZE-HAMMING_SIZE  && m-5 >0){
-               
-                for(i= m-5;i<m+5; i++)
-                   if (an_x[i]<n_c_min){
-                        if (un_only_once >0){
-                           un_only_once =0;
-                       } 
-                       n_c_min= an_x[i] ;
-                       an_exact_ir_valley_locs[k]=i;
-                   }
-                if (un_only_once ==0)   n_exact_ir_valley_locs_count ++ ;
+    //using an_exact_ir_valley_locs , find ir-red DC andir-red AC for SPO2 calibration ratio
+    //finding AC/DC maximum of raw ir * red between two valley locations
+    n_ratio_average =0; 
+    n_i_ratio_count =0; 
+    
+    for(k=0; k< 5; k++) an_ratio[k]=0;
+    for (k=0; k< n_exact_ir_valley_locs_count; k++){
+        if (an_exact_ir_valley_locs[k] > BUFFER_SIZE ){             
+            *pn_spo2 =  -999 ; // do not use SPO2 since valley loc is out of range
+            *pch_spo2_valid  = 0; 
+            return;
+        }
+    }
+    // find max between two valley locations 
+    // and use ratio betwen AC compoent of Ir & Red and DC compoent of Ir & Red for SPO2 
+
+    for (k=0; k< n_exact_ir_valley_locs_count-1; k++){
+        n_y_dc_max= -16777216 ; 
+        n_x_dc_max= - 16777216; 
+        if (an_exact_ir_valley_locs[k+1]-an_exact_ir_valley_locs[k] >10){
+            for (i=an_exact_ir_valley_locs[k]; i< an_exact_ir_valley_locs[k+1]; i++){
+                if (an_x[i]> n_x_dc_max) {n_x_dc_max =an_x[i];n_x_dc_max_idx =i; }
+                if (an_y[i]> n_y_dc_max) {n_y_dc_max =an_y[i];n_y_dc_max_idx=i;}
+            }
+            n_y_ac= (an_y[an_exact_ir_valley_locs[k+1]] - an_y[an_exact_ir_valley_locs[k] ] )*(n_y_dc_max_idx -an_exact_ir_valley_locs[k]); //red
+            n_y_ac=  an_y[an_exact_ir_valley_locs[k]] + n_y_ac/ (an_exact_ir_valley_locs[k+1] - an_exact_ir_valley_locs[k])  ; 
+        
+        
+            n_y_ac=  an_y[n_y_dc_max_idx] - n_y_ac;    // subracting linear DC compoenents from raw 
+            n_x_ac= (an_x[an_exact_ir_valley_locs[k+1]] - an_x[an_exact_ir_valley_locs[k] ] )*(n_x_dc_max_idx -an_exact_ir_valley_locs[k]); // ir
+            n_x_ac=  an_x[an_exact_ir_valley_locs[k]] + n_x_ac/ (an_exact_ir_valley_locs[k+1] - an_exact_ir_valley_locs[k]); 
+            n_x_ac=  an_x[n_y_dc_max_idx] - n_x_ac;      // subracting linear DC compoenents from raw 
+            n_nume=( n_y_ac *n_x_dc_max)>>7 ; //prepare X100 to preserve floating value
+            n_denom= ( n_x_ac *n_y_dc_max)>>7;
+            if (n_denom>0  && n_i_ratio_count <5 &&  n_nume != 0)
+            {   
+                an_ratio[n_i_ratio_count]= (n_nume*100)/n_denom ; //formular is ( n_y_ac *n_x_dc_max) / ( n_x_ac *n_y_dc_max) ;
+                n_i_ratio_count++;
             }
         }
-        if (n_exact_ir_valley_locs_count <2 ){
-           *pn_spo2 =  -999 ; // do not use SPO2 since signal ratio is out of range
-           *pch_spo2_valid  = 0; 
-           return;
-       }
-        // 4 pt MA
-        for(k=0; k< BUFFER_SIZE-MA4_SIZE; k++){
-         an_x[k]=( an_x[k]+an_x[k+1]+ an_x[k+2]+ an_x[k+3])/(int32_t)4;
-         an_y[k]=( an_y[k]+an_y[k+1]+ an_y[k+2]+ an_y[k+3])/(int32_t)4;
-          
-        }
+    }
+
+    maxim_sort_ascend(an_ratio, n_i_ratio_count);
+    n_middle_idx= n_i_ratio_count/2;
+
+    if (n_middle_idx >1)
+        n_ratio_average =( an_ratio[n_middle_idx-1] +an_ratio[n_middle_idx])/2; // use median
+    else
+        n_ratio_average = an_ratio[n_middle_idx ];
 
-        //using an_exact_ir_valley_locs , find ir-red DC andir-red AC for SPO2 calibration ratio
-        //finding AC/DC maximum of raw ir * red between two valley locations
-        n_ratio_average =0; 
-        n_i_ratio_count = 0; 
-        
-        for(k=0; k< 5; k++) an_ratio[k]=0;
-        for (k=0; k< n_exact_ir_valley_locs_count; k++){
-             if (an_exact_ir_valley_locs[k] > BUFFER_SIZE ){             
-                  *pn_spo2 =  -999 ; // do not use SPO2 since valley loc is out of range
-                  *pch_spo2_valid  = 0; 
-                   return;
-             }
-         }
-        // find max between two valley locations 
-        // and use ratio betwen AC compoent of Ir & Red and DC compoent of Ir & Red for SPO2 
-    
-        for (k=0; k< n_exact_ir_valley_locs_count-1; k++){
-              n_y_dc_max= -16777216 ; 
-              n_x_dc_max= - 16777216; 
-           //   printf("range=%d: %d\n ", an_exact_ir_valley_locs[k], an_exact_ir_valley_locs[k+1]);
-              if (an_exact_ir_valley_locs[k+1]-an_exact_ir_valley_locs[k] >10){
-                    for (i=an_exact_ir_valley_locs[k]; i< an_exact_ir_valley_locs[k+1]; i++){
-                
-                          if (an_x[i]> n_x_dc_max) {n_x_dc_max =an_x[i];n_x_dc_max_idx =i; }
-                          if (an_y[i]> n_y_dc_max) {n_y_dc_max =an_y[i];n_y_dc_max_idx=i;}
-                      }
-                    n_y_ac= (an_y[an_exact_ir_valley_locs[k+1]] - an_y[an_exact_ir_valley_locs[k] ] )*(n_y_dc_max_idx -an_exact_ir_valley_locs[k]); //red
-                    n_y_ac=  an_y[an_exact_ir_valley_locs[k]] + n_y_ac/ (an_exact_ir_valley_locs[k+1] - an_exact_ir_valley_locs[k])  ; 
-            
-            
-                    n_y_ac=  an_y[n_y_dc_max_idx] - n_y_ac;    // subracting linear DC compoenents from raw 
-                    n_x_ac= (an_x[an_exact_ir_valley_locs[k+1]] - an_x[an_exact_ir_valley_locs[k] ] )*(n_x_dc_max_idx -an_exact_ir_valley_locs[k]); // ir
-                    n_x_ac=  an_x[an_exact_ir_valley_locs[k]] + n_x_ac/ (an_exact_ir_valley_locs[k+1] - an_exact_ir_valley_locs[k]); 
-                    n_x_ac=  an_x[n_y_dc_max_idx] - n_x_ac;      // subracting linear DC compoenents from raw 
-                    n_nume=( n_y_ac *n_x_dc_max)>>7 ; //prepare X100 to preserve floating value
-                    n_denom= ( n_x_ac *n_y_dc_max)>>7;
-                    if (n_denom>0  && n_i_ratio_count <5 &&  n_nume != 0)
-                    {   
-                         an_ratio[n_i_ratio_count]= (n_nume*100)/n_denom ; //formular is ( n_y_ac *n_x_dc_max) / ( n_x_ac *n_y_dc_max) ;
-                         n_i_ratio_count++;
-                    }
-              }
-            
-    //  prlongf("an_ratio[%d]= %d an_exact_ir_valley_locs[k] =%d , an_exact_ir_valley_locs[%d] =%d \n",k, an_ratio[k] ,an_exact_ir_valley_locs[k] ,k+1,  an_exact_ir_valley_locs[k+1]  ) ;
-    //  prlongf("n_nume= %d ,n_denom= %d  n_y_ac = %d, n_x_dc_max = %d, n_x_ac= %d, n_y_dc_max = %d\n",n_nume, n_denom,  n_y_ac ,n_x_dc_max ,n_x_ac ,n_y_dc_max );
-
-        }
-
-        maxim_sort_ascend(an_ratio, n_i_ratio_count);
-        n_middle_idx= n_i_ratio_count/2;
-
-        if (n_middle_idx >1)
-          n_ratio_average =( an_ratio[n_middle_idx-1] +an_ratio[n_middle_idx])/2; // use median
-        else
-           n_ratio_average = an_ratio[n_middle_idx ];
-
-        if( n_ratio_average>2 && n_ratio_average <184){
-                   n_spo2_calc= uch_spo2_table[n_ratio_average] ;
-            *pn_spo2 = n_spo2_calc ;
-            *pch_spo2_valid  = 1;//  float_SPO2 =  -45.060*n_ratio_average* n_ratio_average/10000 + 30.354 *n_ratio_average/100 + 94.845 ;  // for comparison with table
-        }
-        else{
-            *pn_spo2 =  -999 ; // do not use SPO2 since signal ratio is out of range
-            *pch_spo2_valid  = 0; 
-        }
-            
-
+    if( n_ratio_average>2 && n_ratio_average <184){
+        n_spo2_calc= uch_spo2_table[n_ratio_average] ;
+        *pn_spo2 = n_spo2_calc ;
+        *pch_spo2_valid  = 1;//  float_SPO2 =  -45.060*n_ratio_average* n_ratio_average/10000 + 30.354 *n_ratio_average/100 + 94.845 ;  // for comparison with table
+    }
+    else{
+        *pn_spo2 =  -999 ; // do not use SPO2 since signal ratio is out of range
+        *pch_spo2_valid  = 0; 
+    }
 }
 
 
-void maxim_find_peaks( int32_t *pn_locs, int32_t *pn_npks,  int32_t  *pn_x, int32_t n_size, int32_t n_min_height, int32_t n_min_distance, int32_t n_max_num )
+void maxim_find_peaks(int32_t *pn_locs, int32_t *pn_npks, int32_t *pn_x, int32_t n_size, int32_t n_min_height, int32_t n_min_distance, int32_t n_max_num)
 /**
 * \brief        Find peaks
 * \par          Details
@@ -280,7 +265,7 @@
     *pn_npks = min( *pn_npks, n_max_num );
 }
 
-void maxim_peaks_above_min_height( int32_t *pn_locs, int32_t *pn_npks,  int32_t  *pn_x, int32_t n_size, int32_t n_min_height )
+void maxim_peaks_above_min_height(int32_t *pn_locs, int32_t *pn_npks, int32_t  *pn_x, int32_t n_size, int32_t n_min_height)
 /**
 * \brief        Find peaks above n_min_height
 * \par          Details
@@ -299,7 +284,7 @@
                 n_width++;
             if (pn_x[i] > pn_x[i+n_width] && (*pn_npks) < 15 ){                            // find right edge of peaks
                 pn_locs[(*pn_npks)++] = i;        
-              // for flat peaks, peak location is left edge
+                // for flat peaks, peak location is left edge
                 i += n_width+1;
             }
             else
@@ -311,7 +296,7 @@
 }
 
 
-void maxim_remove_close_peaks( int32_t *pn_locs, int32_t *pn_npks,  int32_t  *pn_x, int32_t n_min_distance )
+void maxim_remove_close_peaks(int32_t *pn_locs, int32_t *pn_npks, int32_t *pn_x,int32_t n_min_distance)
 /**
 * \brief        Remove peaks
 * \par          Details
@@ -340,7 +325,7 @@
     maxim_sort_ascend( pn_locs, *pn_npks );
 }
 
-void maxim_sort_ascend(int32_t  *pn_x, int32_t n_size) 
+void maxim_sort_ascend(int32_t *pn_x,int32_t n_size) 
 /**
 * \brief        Sort array
 * \par          Details
@@ -358,7 +343,7 @@
     }
 }
 
-void maxim_sort_indices_descend(  int32_t  *pn_x, int32_t *pn_indx, int32_t n_size)
+void maxim_sort_indices_descend(int32_t *pn_x, int32_t *pn_indx, int32_t n_size)
 /**
 * \brief        Sort indices
 * \par          Details