Updated peak detection example

Author: tigoe

PeakDetection/PeakDetection.ino

@@ -1,59 +1,39 @@
 /*
 Peak Finder
- 
- This example finds the peak value of an analog sensor over time. 
+
+ This example finds the peak value of an analog sensor over time.
  It assumes the sensor is moving in a simple curve.
- 
- The program checks to see that the current value is above a given threshold, 
- then checks to see if the value is greater than the previous value. if so, 
- then it saves the current value as a peak. When the current value goes below 
+
+ The program checks to see that the current value is above a given threshold,
+ then checks to see if the value is greater than the previous value. if so,
+ then it saves the current value as a peak. When the current value goes below
  the threshold again, it outputs the last peak value recorded.
- 
- This works only with sensors that settle at zero or below.  Accelerometers
- and other sensors that settle in the middle of their range require a 
- more complex solution.
- 
+
  created 12 Sept. 2005
- modified 20 March 2012
+ modified 9 Sept. 2014
  by Tom Igoe
- 
+
  */
 
 int peakValue = 0;
-int sensorValue = 0;
-int lastSensorValue = 0;
-int threshold = 50;             //set your own value based on your sensors
-int noise = 5;                  //set a noise value based on your particular sensor
+int threshold = 50;   //set your own value based on your sensors
+int noise = 5;        //set a noise value based on your particular sensor
 
 void setup() {
   Serial.begin(9600);
 }
 
 void loop() {
   //read sensor on pin A0:
-  sensorValue = analogRead(A0);
-
-  //check to see that it's above the threshold:
-  if ( sensorValue >= threshold + noise ) { 
-    //if it's greater than the last eading,
-    // then make it our current peak:
-    if ( sensorValue >= lastSensorValue + noise ) { 
-      peakValue = sensorValue;
-    }
-    //if the sensorValue is not above the threshold,
-    // then  the last peak value you got would be the actual peak:
-  } 
-  else {
-    if ( peakValue >= threshold ) { 
-      //this is the final peak value; take action
-      Serial.print("peak reading: ");
+  int sensorValue = analogRead(A0);
+  // check if it's higher than the current peak:
+  if (sensorValue > peakValue) {
+    peakValue = sensorValue;
+  }
+  if (sensorValue <= threshold - noise ) {
+    if (peakValue > threshold + noise) {
       Serial.println(peakValue);
+      peakValue = 0;
     }
-
-    //reset peakValue, since youyou've finished with this peak:
-    peakValue = 0;
   }
-
-  //store the current sensor value for the next loop:
-  lastSensorValue = sensorValue;
 }