add pulseFilter

Author: RCmags

README.md

@@ -0,0 +1,50 @@
+/* This sketch shows how to filter signals */
+
+// ---- Create servo object to generate PWM signals ---
+#include <Servo.h>
+Servo servo;
+
+// ----------- Signal deadband and calibration --------
+#include <PulseInput.h> 
+volatile unsigned int input;        /* variable is required to capture signal */
+
+#define BAND    12                  /* Deadband. Changes in signal within this band are ignored. 
+                                       Large values result in a steadier signal, at cost of lower precision */
+                               
+PulseFilter <&input, BAND> filter;
+
+// Simpler form:
+//PulseFilter <&input> filter;     /* The filter defaults to a deadband of 4 if none is specified */
+
+// ----------------------------------------------------
+
+void setup() {
+  Serial.begin(9600);
+  
+  // PWM output at pin 2
+  servo.attach(2);   
+  servo.writeMicroseconds(1000); // initial signal value     
+  
+  // assign variables to receive signals 
+  attachPulseInput(8, input);
+   
+  // subtract initial average from input
+  /*
+  delay(1000);              // pause before reading values [required for proper calibration]
+  filter.calibrate();       // comment to only filter signal
+  */
+}
+
+void loop() {
+  // generate variable signal:
+  int target = analogRead(A0) + 1000;   // read potentiometer from A0
+  servo.writeMicroseconds(target);
+  
+  // display comparison:
+  Serial.print( "Raw: " ); 
+  Serial.print( input );            
+  
+  Serial.print("\t Filter: ");
+  Serial.print( filter.update() );
+  Serial.println();
+}

examples/filter/filter.ino

@@ -0,0 +1,28 @@
+/* This sketch shows how to read PWM signals for servos */
+
+// Create servo objects to generate signals
+#include <Servo.h>
+Servo servo;
+
+// 1. Each signal must be read with an volatile unsigned int
+#include <PulseInput.h>   
+volatile unsigned int input;    /* each signal requires a variable - MUST be volatile unsigned int */
+
+void setup() {
+  // 2. assign variables to receive signal 
+  attachPulseInput(8, input);  // pin 8 as INPUT_PULLUP
+
+  /* Generate pwm signals [in us] */
+  servo.attach(2);                 // Output at PIN 2
+  servo.writeMicroseconds(1500);   // ON time = 1500 us
+     
+  Serial.begin(9600);
+
+  /* To stop reading an already specified input, use this function: */
+  //detachPulseInput(8);        // Stop reading input at pin 8
+}
+
+void loop() {  
+  // read signal variable
+  Serial.println(input);
+}

examples/read/read.ino

@@ -1,4 +1,5 @@
-pulseInput	KEYWORD1
+PulseInput	KEYWORD1
+PulseFilter	KEYWORD1
 attachPulseInput	KEYWORD2
 detachPulseInput	KEYWORD2
 

keywords.txt

@@ -1,5 +1,5 @@
 name=pulseInput
-version=1.0.0
+version=1.1.0
 author=RCmags <memoryofatrufestival@gmail.com>
 maintainer=RCmags <memoryofatrufestival@gmail.com>
 sentence=Non-blocking alternative to pulseIn 

library.properties

@@ -0,0 +1,49 @@
+#ifndef PulseFilter_h
+#define PulseFilter_h
+
+//--------- Constants --------
+
+#define N_SAMPLE 		25			// Samples used to calculate average
+#define DEFAULT_BAND	4			// Error range of deadband filter. Changes in signal within this band are ignored.
+
+//---------- Class -----------
+
+template<volatile uint16_t* input, int BAND = DEFAULT_BAND> 	
+class PulseFilter {
+  private:
+    uint16_t mean=0;
+    int filter=0; 
+  
+  public:
+	/* input average */
+    void calibrate() {
+      uint32_t sum = 0;
+      for( int count = 0; count < N_SAMPLE; count += 1 ) {
+        sum += (*input);
+        delay(20);			// period of 50hz pwm signal    
+      }
+      // store truncated mean
+      float f_mean = float(sum)/float(N_SAMPLE);
+      mean = uint16_t(f_mean);
+    }
+
+	/* update and return output */
+    int update() {
+      int value = int(*input) - int(mean); 
+      // deadband 
+      int change = value - filter;
+      if( change > BAND ) {
+        filter += change - BAND;
+      } else if ( change < -BAND ) {
+        filter += change + BAND;
+      }
+      return filter;
+    }
+};
+
+//------- Clear labels -------
+
+#undef N_SAMPLE
+#undef DEFAULT_BAND
+
+#endif

src/PulseFilter.h

@@ -1,4 +1,5 @@
 #include <PinChangeInterrupt.h>
+#include <PulseFilter.h>
 
 #ifndef PulseInput_h
 #define PulseInput_h