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libraries/audio-tools/examples/examples-audiokit/streams-audiokit-goertzel/streams-audiokit-goertzel.ino

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+// Example for DTMF detection using Goertzel algorithm
+// Uses AudioKit and I2S microphones as input
+
+#include "AudioTools.h"
+#include "AudioTools/AudioLibs/AudioBoardStream.h"
+
+AudioInfo info(44100, 2, 16);             // 8kHz, mono, 16 bits
+AudioBoardStream kit(AudioKitEs8388V1);  // Access I2S as stream
+//CsvOutput<int16_t> out(Serial, 1);
+GoertzelStream goertzel; //(out);
+StreamCopy copier(goertzel, kit);  // copy kit to georzel
+
+// represent DTMF keys
+class DTMF {
+ public:
+  enum Dimension { Row, Col };
+  DTMF() = default;
+  DTMF(Dimension d, int i) {
+    if (d == Row)
+      row = i;
+    else
+      col = i;
+  }
+  void clear() {
+    row = -1;
+    col = -1;
+  }
+  char getChar() {
+    if (row == -1 || col == -1) return '?';
+    return keys[row][col];
+  }
+  int row = -1;
+  int col = -1;
+  const char* keys[4] = {"123A", "456B", "789C", "*0#D"};
+} actual_dtmf;
+
+// combine row and col information
+void GoetzelCallback(float frequency, float magnitude, void* ref) {
+  DTMF* dtmf = (DTMF*)ref;
+  LOGW("Time: %lu - Hz: %f  Mag: %f", millis(), frequency, magnitude);
+  // we get either row or col information
+  if (dtmf->row != -1) {
+    actual_dtmf.row = dtmf->row;
+  } else {
+    actual_dtmf.col = dtmf->col;
+
+    // print detected key
+    Serial.println(actual_dtmf.getChar());
+    actual_dtmf.clear();
+  }
+}
+
+void setup() {
+  Serial.begin(115200);
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);
+
+  // start audio input from microphones
+  auto cfg = kit.defaultConfig(RX_MODE);
+  cfg.copyFrom(info);
+  cfg.sd_active = false;
+  cfg.input_device = ADC_INPUT_LINE2;
+  cfg.use_apll = false;
+  kit.begin(cfg);
+
+  // lower frequencies - with keys
+  goertzel.addFrequency(697, new DTMF(DTMF::Row, 0));
+  goertzel.addFrequency(770, new DTMF(DTMF::Row, 1));
+  goertzel.addFrequency(852, new DTMF(DTMF::Row, 2));
+  goertzel.addFrequency(941, new DTMF(DTMF::Row, 3));
+  // higher frequencies with idx
+  goertzel.addFrequency(1209, new DTMF(DTMF::Col, 0));
+  goertzel.addFrequency(1336, new DTMF(DTMF::Col, 1));
+  goertzel.addFrequency(1477, new DTMF(DTMF::Col, 2));
+  goertzel.addFrequency(1633, new DTMF(DTMF::Col, 3));
+  // define callback
+  goertzel.setFrequencyDetectionCallback(GoetzelCallback);
+
+  // start goertzel
+  auto gcfg = goertzel.defaultConfig();
+  gcfg.copyFrom(info);
+  gcfg.threshold = 5.0;
+  gcfg.block_size = 1024;
+  goertzel.begin(gcfg);
+}
+
+void loop() { copier.copy(); }