implement DC offset check inspired by Pull Request 107 by 3hhh

Author: corrados

edrumulus.cpp

@@ -25,6 +25,8 @@ Edrumulus::Edrumulus()
   error_LED_blink_time       = round ( error_LED_blink_time_s * Fs );
   dc_offset_est_len          = round ( dc_offset_est_len_s * Fs );
   samplerate_max_cnt         = round ( samplerate_max_cnt_len_s * Fs );
+  dc_offset_min_limit        = round(ADC_MAX_RANGE / 2 - ADC_MAX_RANGE * dc_offset_max_rel_error);
+  dc_offset_max_limit        = round(ADC_MAX_RANGE / 2 + ADC_MAX_RANGE * dc_offset_max_rel_error);
   overload_LED_cnt           = 0;
   error_LED_cnt              = 0;
   status_is_overload         = false;
@@ -337,7 +339,7 @@ Serial.println ( serial_print );
   }
 
 
-  // Sampling rate check -------------------------------------------------------
+  // Sampling rate and DC offset check -----------------------------------------
   // (i.e. if CPU is overloaded, the sample rate will drop which is bad)
   if ( samplerate_prev_micros_cnt >= samplerate_max_cnt )
   {
@@ -357,26 +359,23 @@ Serial.println ( serial_print );
     samplerate_prev_micros_cnt = 0;
     samplerate_prev_micros     = samplerate_cur_micros;
 
-/*
-// TEST check DC offset values
-String serial_print;
-String serial_print2;
-for ( int i = 0; i < number_pads; i++ )
-{
-  if ( !pad[i].get_is_control() )
-  {
-    for ( int j = 0; j < number_inputs[i]; j++ )
+    // DC offset check
+    for ( int i = 0; i < number_pads; i++ )
     {
-      serial_print += String ( sample_org[i][j] ) + "\t" + String ( dc_offset[i][j] ) + "\t";
-      serial_print2 += String ( sample_org[i][j] - dc_offset[i][j] ) + "\t";
+      if ( !pad[i].get_is_control() )
+      {
+        for ( int j = 0; j < number_inputs[i]; j++ )
+        {
+          const float& cur_dc_offset = dc_offset[i][j];
+//Serial.println ( cur_dc_offset ); // TEST for plotting all DC offsets
+          if ( ( cur_dc_offset < dc_offset_min_limit ) || ( cur_dc_offset > dc_offset_max_limit ) )
+          {
+            status_is_error = true;
+          }
+        }
+      }
     }
   }
-}
-//Serial.println ( serial_print );
-Serial.println ( serial_print2 );
-*/
-
-  }
   samplerate_prev_micros_cnt++;
   error_LED_cnt++;
 }

edrumulus.h

@@ -533,6 +533,7 @@ const float ADC_noise_peak_velocity_scaling = 1.0f / 6.0f;
   const float dc_offset_est_len_s      = 1.25f; // length of initial DC offset estimation in seconds
   const int   samplerate_max_cnt_len_s = 1.25f; // time interval for sampling rate estimation in seconds
   const int   samplerate_max_error_Hz  = 200;   // tolerate a sample rate deviation of 200 Hz
+  const float dc_offset_max_rel_error  = 0.25f; // DC offset limit from ADC middle position, where offset is defined relative to ADC maximum value
   const int   cancel_time_ms           = 30;    // on same stand approx. 10 ms + some margin (20 ms)
   const float overload_LED_on_time_s   = 0.25f; // minimum overload LED on time (e.g., 250 ms)
   const float error_LED_blink_time_s   = 0.25f; // LED blink time on error (e.g., 250 ms)
@@ -576,6 +577,8 @@ const float ADC_noise_peak_velocity_scaling = 1.0f / 6.0f;
   int                samplerate_max_cnt;
   int                samplerate_prev_micros_cnt;
   unsigned long      samplerate_prev_micros;
+  int                dc_offset_min_limit;
+  int                dc_offset_max_limit;
   Pad                pad[MAX_NUM_PADS];
   bool               peak_found[MAX_NUM_PADS];
   bool               control_found[MAX_NUM_PADS];