Removed digital filter. Updated everything to do integer math.

Author: finnkuusisto

Devlpr.cpp

@@ -1,11 +1,11 @@
 #include "Arduino.h"
 #include "Devlpr.h"
 
-Devlpr::Devlpr()
+Devlpr::Devlpr(int pin)
 {
-    bufInd = BUFSIZE - 1;
-    emgPin = A0;
+    emgPin = pin;
     emgRunningSum = 0;
+    bufInd = BUFSIZE - 1;
 }
 
 void Devlpr::tick()
@@ -29,42 +29,21 @@ void Devlpr::tick()
     lastTickMicros = currMicros;
 }
 
-int Devlpr::lastValue()
+unsigned int Devlpr::lastValue()
 {
     return buf[bufInd];
 }
 
-int filt[93] = {24, 23, 100, 109, 130, 128, 81, 68, -39, -41, -181, -140, -280, -170, -294, -109, -225, 14, -124, 134, -61, 184, -87, 136, -205, 14, -365, -115, -491, -176, -523, -132, -450, -4, -320, 140, -215, 218, -204, 181, -306, 43, -479, -128, -637, -244, 9329, -244, -637, -128, -479, 43, -306, 181, -204, 218, -215, 140, -320, -4, -450, -132, -523, -176, -491, -115, -365, 14, -205, 136, -87, 184, -61, 134, -124, 14, -225, -109, -294, -170, -280, -140, -181, -41, -39, 68, 81, 128, 130, 109, 100, 23, 24};
-float filtFactor = 10000.0; // the multiplier on the integral filter
-float Devlpr::lastValueFiltered()
+unsigned int Devlpr::windowAvg()
 {
-    // should help to roughly recenter data (use quick integral math)
-    long sampAvg = emgRunningSum / BUFSIZE;
-    // the buffer is the same size as the filter so filtered data
-    // will be roughly len/2 ticks in the past
-    long ret = 0;
-    int currInd = bufInd + 1; // start at the tail
-    // the filter is also symmetric, so convolve=linear combination
-    for (int i = 0; i < BUFSIZE; i++) {
-        // check the current circular buffer index
-        if (currInd >= BUFSIZE) { // faster than modulo
-            currInd = 0;
-        }
-        // we will need to coerce the ints to longs to avoid overflow
-        long filtVal = (long)filt[i];
-        long sampVal = (long)buf[currInd] - sampAvg;
-        // do the multiply/add
-        ret = ret + (filtVal * sampVal);
-        // and update the current buffer index for next
-        currInd++;
-    }
-    // our integral filter is multiplied by some factor, so correct
-    return ret / filtFactor;
+    return emgRunningSum / BUFSIZE;
 }
 
-float Devlpr::windowAvg()
+int Devlpr::lastValueCentered()
 {
-    return emgRunningSum / float(BUFSIZE);
+    int lastVal = lastValue();
+    int wAvg = windowAvg();
+    return lastVal - wAvg;
 }
 
 void Devlpr::readEMG()
@@ -73,7 +52,7 @@ void Devlpr::readEMG()
     // so update bufInd before the read
     bufInd++;
     // circular buffer
-    if (bufInd >= BUFSIZE) { // surprisingly faster than mod
+    if (bufInd >= BUFSIZE) { // faster than mod
         bufInd = 0;
     }
     // read our new value

Devlpr.h

@@ -6,23 +6,24 @@
 class Devlpr
 {
     public:
-        Devlpr();
+        Devlpr(int pin=A0);
         void tick();
-        int lastValue();
-        float lastValueFiltered();
-        float windowAvg();
+        unsigned int lastValue();
+        int lastValueCentered();
+        unsigned int windowAvg();
     private:
         // general buffer bookkeeping
-        static const byte BUFSIZE = 93; // size of filter
+        static const byte BUFSIZE = 32; // power of 2 for integer avg calc
+        unsigned int buf[BUFSIZE];
         byte bufInd;
-        int buf[BUFSIZE];
+        // scheduling
+        unsigned long MICROS_SCHED_EMG = 1000;
         unsigned long lastTickMicros = 0;
+        unsigned long microsSinceEMG = 0;
         // emg tracking
-        unsigned long MICROS_SCHED_EMG = 1000;
-        unsigned long microsSinceEMG;
-        unsigned long emgRunningSum;
         int emgPin;
-        int emgVal;
+        unsigned int emgVal; // ATMEGA boards have 10-bit ADC (0-1023)
+        unsigned int emgRunningSum; // if BUFSIZE is small, uint is fine
         void readEMG();
 };
 

libdevlpr.ino

@@ -3,27 +3,27 @@
 Devlpr devlpr;
 
 void setup() {
-    Serial.begin(9600);
+    Serial.begin(2000000);
 }
 
-unsigned long microsSinceFilteredCall = 0;
+unsigned long microsSincePrint = 0;
 unsigned long prevLoopMicros = 0;
-float result = 0.0;
+int result = 0;
 void loop() {
     // let the DEVLPR library do its job
     devlpr.tick();
 
-    // try to sample filtered data at 1000Hz
+    // try to sample and print data at 1000Hz
     unsigned long currMicros = micros();
     unsigned long microsDelta = currMicros - prevLoopMicros;
-    microsSinceFilteredCall += microsDelta;
+    microsSincePrint += microsDelta;
     // has 1ms passed
-    if (microsSinceFilteredCall > 1000) {
+    if (microsSincePrint > 1000) {
         // 1ms has passed, get the value
-        result = devlpr.lastValueFiltered();
+        result = devlpr.lastValueCentered();
         Serial.println(result);
         // update our last filtered call
-        microsSinceFilteredCall = 0;
+        microsSincePrint = 0;
     }
     // update our last loop time
     prevLoopMicros = currMicros;