Add the fir_filer sketch to the examples directory

examples/fir_filter/bandp_1200_1700.h

+
+/* .fir file parameters which generated these coefficients
+100 1 3 16 32768 44100
+0 500 1200 1700 2300 
+ 0.0000  1.0000  0.0000 
+70.0000  1.0000 70.0000 
+*/
+	(short)0xFFAA,
+	(short)0xFFC5,
+	(short)0xFFB6,
+	(short)0xFFA7,
+	(short)0xFF9B,
+	(short)0xFF94,
+	(short)0xFF93,
+	(short)0xFF9A,
+	(short)0xFFAA,
+	(short)0xFFC4,
+	(short)0xFFE9,
+	(short)0x0017,
+	(short)0x004F,
+	(short)0x008E,
+	(short)0x00D1,
+	(short)0x0115,
+	(short)0x0155,
+	(short)0x018F,
+	(short)0x01BC,
+	(short)0x01D9,
+	(short)0x01E2,
+	(short)0x01D3,
+	(short)0x01AB,
+	(short)0x0168,
+	(short)0x010A,
+	(short)0x0095,
+	(short)0x000B,
+	(short)0xFF72,
+	(short)0xFED1,
+	(short)0xFE2E,
+	(short)0xFD92,
+	(short)0xFD06,
+	(short)0xFC92,
+	(short)0xFC3D,
+	(short)0xFC0D,
+	(short)0xFC08,
+	(short)0xFC30,
+	(short)0xFC85,
+	(short)0xFD06,
+	(short)0xFDAF,
+	(short)0xFE79,
+	(short)0xFF5C,
+	(short)0x004D,
+	(short)0x0143,
+	(short)0x0231,
+	(short)0x030D,
+	(short)0x03CB,
+	(short)0x0463,
+	(short)0x04CC,
+	(short)0x0502,
+	(short)0x0502,
+	(short)0x04CC,
+	(short)0x0463,
+	(short)0x03CB,
+	(short)0x030D,
+	(short)0x0231,
+	(short)0x0143,
+	(short)0x004D,
+	(short)0xFF5C,
+	(short)0xFE79,
+	(short)0xFDAF,
+	(short)0xFD06,
+	(short)0xFC85,
+	(short)0xFC30,
+	(short)0xFC08,
+	(short)0xFC0D,
+	(short)0xFC3D,
+	(short)0xFC92,
+	(short)0xFD06,
+	(short)0xFD92,
+	(short)0xFE2E,
+	(short)0xFED1,
+	(short)0xFF72,
+	(short)0x000B,
+	(short)0x0095,
+	(short)0x010A,
+	(short)0x0168,
+	(short)0x01AB,
+	(short)0x01D3,
+	(short)0x01E2,
+	(short)0x01D9,
+	(short)0x01BC,
+	(short)0x018F,
+	(short)0x0155,
+	(short)0x0115,
+	(short)0x00D1,
+	(short)0x008E,
+	(short)0x004F,
+	(short)0x0017,
+	(short)0xFFE9,
+	(short)0xFFC4,
+	(short)0xFFAA,
+	(short)0xFF9A,
+	(short)0xFF93,
+	(short)0xFF94,
+	(short)0xFF9B,
+	(short)0xFFA7,
+	(short)0xFFB6,
+	(short)0xFFC5,
+	(short)0xFFAA,
+

examples/fir_filter/filters.cpp

+#include "filters.h"
+short low_pass[NUM_COEFFS] = {
+#include "lopass_4000_44100.h"
+};
+
+short band_pass[NUM_COEFFS] = {
+#include "bandp_1200_1700.h"
+};

examples/fir_filter/filters.h

+// Number of coefficients
+#define NUM_COEFFS 100
+extern short low_pass[];
+extern short band_pass[];
+

examples/fir_filter/fir_filter.ino

+/*
+
+The audio board uses the following pins.
+ 6 - MEMCS
+ 7 - MOSI
+ 9 - BCLK
+10 - SDCS
+11 - MCLK
+12 - MISO
+13 - RX
+14 - SCLK
+15 - VOL
+18 - SDA
+19 - SCL
+22 - TX
+23 - LRCLK
+
+*/
+
+//#include <arm_math.h>
+#include <Audio.h>
+#include <Wire.h>
+#include <SD.h>
+#include <SPI.h>
+#include <Bounce.h>
+#include "filters.h"
+
+// If this pin is grounded the FIR filter is turned which
+// makes just pass through the audio
+// Don't use any of the pins listed above
+#define PASSTHRU_PIN 1
+// If this pin goes low the next FIR filter in the list
+// is switched in.
+#define FILTER_PIN 0
+
+Bounce b_passthru = Bounce(PASSTHRU_PIN,15);
+Bounce b_filter   = Bounce(FILTER_PIN,15);
+
+//const int myInput = AUDIO_INPUT_MIC;
+const int myInput = AUDIO_INPUT_LINEIN;
+
+
+AudioInputI2S       audioInput;         // audio shield: mic or line-in
+AudioFilterFIR           myFilter;
+AudioOutputI2S      audioOutput;        // audio shield: headphones & line-out
+
+// Create Audio connections between the components
+// Both channels of the audio input go to the FIR filter
+AudioConnection c1(audioInput, 0, myFilter, 0);
+AudioConnection c2(audioInput, 1, myFilter, 1);
+// both channels from the FIR filter go to the audio output
+AudioConnection c3(myFilter, 0, audioOutput, 0);
+AudioConnection c4(myFilter, 1, audioOutput, 1);
+AudioControlSGTL5000 audioShield;
+
+
+struct fir_filter {
+  short *coeffs;
+  short num_coeffs;
+};
+
+// index of current filter. Start with the low pass.
+int fir_idx = 0;
+struct fir_filter fir_list[] = {
+  low_pass , 100,    // low pass with cutoff at 1kHz and -60dB at 2kHz
+  band_pass, 100,    // bandpass 1200Hz - 1700Hz
+  NULL,      0
+};
+
+
+void setup() {
+  
+  Serial.begin(9600);
+  while (!Serial) ;
+  delay(3000);
+
+  pinMode(PASSTHRU_PIN,INPUT_PULLUP);
+  pinMode(FILTER_PIN,INPUT_PULLUP);
+
+  // It doesn't work properly with any less than 8
+  AudioMemory(8);
+
+  audioShield.enable();
+  audioShield.inputSelect(myInput);
+  audioShield.volume(50);
+  
+  // Warn that the passthru pin is grounded
+  if(!digitalRead(PASSTHRU_PIN)) {
+    Serial.print("PASSTHRU_PIN (");
+    Serial.print(PASSTHRU_PIN);
+    Serial.println(") is grounded");
+  }
+
+  // Warn that the filter pin is grounded
+  if(!digitalRead(FILTER_PIN)) {
+    Serial.print("FILTER_PIN (");
+    Serial.print(FILTER_PIN);
+    Serial.println(") is grounded");
+  }  
+  // Initialize the filter
+  myFilter.begin(fir_list[0].coeffs,fir_list[0].num_coeffs);
+  
+  Serial.println("setup done");
+}
+
+// index of current filter when passthrough is selected
+int old_idx = -1;
+
+// audio volume
+int volume = 0;
+
+void loop()
+{
+  // Volume control
+  int n = analogRead(15);
+  if (n != volume) {
+    volume = n;
+    audioShield.volume((float)n / 10.23);
+  }
+  
+  // update the two buttons
+  b_passthru.update();
+  b_filter.update();
+  
+
+  
+  // If the passthru button is pushed, save the current
+  // filter index and then switch the filter to passthru
+  if(b_passthru.fallingEdge()) {
+    old_idx = fir_idx;
+    myFilter.begin(FIR_PASSTHRU,0);
+  }
+  
+  // If passthru button is released, restore previous filter
+  if(b_passthru.risingEdge()) {
+    if(old_idx != -1)myFilter.begin(fir_list[fir_idx].coeffs,fir_list[fir_idx].num_coeffs);
+    old_idx = -1;
+  }
+  
+  // switch to next filter in the list
+  if(b_filter.fallingEdge()) {
+    fir_idx++;
+    if(fir_list[fir_idx].num_coeffs == 0)fir_idx = 0;
+    myFilter.begin(fir_list[fir_idx].coeffs,fir_list[fir_idx].num_coeffs);
+  }
+}
+
+
+

examples/fir_filter/lopass_4000_44100.h

+
+/* .fir file parameters which generated these coefficients
+100 1 2 16 32768 44100
+0 1000 2000 
+ 1.0000  0.0000 
+ 1.0000 70.0000 
+*/
+	(short)0x0015,
+	(short)0x0011,
+	(short)0x0017,
+	(short)0x001E,
+	(short)0x0025,
+	(short)0x002C,
+	(short)0x0032,
+	(short)0x0037,
+	(short)0x003B,
+	(short)0x003C,
+	(short)0x003B,
+	(short)0x0036,
+	(short)0x002E,
+	(short)0x0021,
+	(short)0x000F,
+	(short)0xFFF9,
+	(short)0xFFDE,
+	(short)0xFFBF,
+	(short)0xFF9C,
+	(short)0xFF76,
+	(short)0xFF4F,
+	(short)0xFF27,
+	(short)0xFF02,
+	(short)0xFEDF,
+	(short)0xFEC2,
+	(short)0xFEAC,
+	(short)0xFEA0,
+	(short)0xFE9F,
+	(short)0xFEAC,
+	(short)0xFEC8,
+	(short)0xFEF4,
+	(short)0xFF31,
+	(short)0xFF7F,
+	(short)0xFFDF,
+	(short)0x0050,
+	(short)0x00D0,
+	(short)0x015E,
+	(short)0x01F8,
+	(short)0x029A,
+	(short)0x0341,
+	(short)0x03EA,
+	(short)0x0491,
+	(short)0x0532,
+	(short)0x05CA,
+	(short)0x0653,
+	(short)0x06CC,
+	(short)0x0731,
+	(short)0x077F,
+	(short)0x07B4,
+	(short)0x07CF,
+	(short)0x07CF,
+	(short)0x07B4,
+	(short)0x077F,
+	(short)0x0731,
+	(short)0x06CC,
+	(short)0x0653,
+	(short)0x05CA,
+	(short)0x0532,
+	(short)0x0491,
+	(short)0x03EA,
+	(short)0x0341,
+	(short)0x029A,
+	(short)0x01F8,
+	(short)0x015E,
+	(short)0x00D0,
+	(short)0x0050,
+	(short)0xFFDF,
+	(short)0xFF7F,
+	(short)0xFF31,
+	(short)0xFEF4,
+	(short)0xFEC8,
+	(short)0xFEAC,
+	(short)0xFE9F,
+	(short)0xFEA0,
+	(short)0xFEAC,
+	(short)0xFEC2,
+	(short)0xFEDF,
+	(short)0xFF02,
+	(short)0xFF27,
+	(short)0xFF4F,
+	(short)0xFF76,
+	(short)0xFF9C,
+	(short)0xFFBF,
+	(short)0xFFDE,
+	(short)0xFFF9,
+	(short)0x000F,
+	(short)0x0021,
+	(short)0x002E,
+	(short)0x0036,
+	(short)0x003B,
+	(short)0x003C,
+	(short)0x003B,
+	(short)0x0037,
+	(short)0x0032,
+	(short)0x002C,
+	(short)0x0025,
+	(short)0x001E,
+	(short)0x0017,
+	(short)0x0011,
+	(short)0x0015,
+
+