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libraries/audio-tools/examples/examples-basic-api/base-adc-average-mono-serial/base-adc-average-mono-serial.ino

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+/**
+ * @file base-adc-average-mono-serial.ino
+ * @brief Attempts down sampling with binning of a mono audio signal by AVG_LEN
+ * @author Urs Utzinger
+ * @copyright GPLv3
+ **/
+
+#include "Arduino.h"
+#include "AudioTools.h"
+
+// On board analog to digital converter
+AnalogAudioStream analog_in; 
+
+// Serial terminal output
+CsvOutput<int16_t> serial_out(Serial);
+
+#define BAUD_RATE   500000
+#define SAMPLE_RATE 44100
+#define BUFFER_SIZE 256
+#define AVG_LEN 64
+#define BYTES_PER_SAMPLE sizeof(int16_t)
+
+// buffer to read samples and store the average samples
+int16_t buffer[BUFFER_SIZE];
+
+void setup() {
+  
+  delay(3000); // wait for serial to become available
+
+  // Serial Interface
+  Serial.begin(BAUD_RATE);
+
+  // Include logging to serial
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Error); // Debug, Warning, Info, Error
+  
+  // Start ADC input
+  Serial.println("Starting ADC...");
+  auto adcConfig = analog_in.defaultConfig(RX_MODE);
+  adcConfig.sample_rate = SAMPLE_RATE;
+  adcConfig.channels = 1; 
+
+  // For ESP32 by Espressif Systems version 3.0.0 and later:
+  // see examples/README_ESP32.md
+  // adcConfig.sample_rate = 44100;
+  // adcConfig.adc_bit_width = 12;
+  // adcConfig.adc_calibration_active = true;
+  // adcConfig.is_auto_center_read = false;
+  // adcConfig.adc_attenuation = ADC_ATTEN_DB_12; 
+  // adcConfig.channels = 1;
+  // adcConfig.adc_channels[0] = ADC_CHANNEL_4; 
+
+  analog_in.begin(adcConfig);
+
+  // Start Serial Output CSV
+  Serial.println("Starting Serial Out...");
+  auto csvConfig = serial_out.defaultConfig();
+  csvConfig.sample_rate = SAMPLE_RATE/AVG_LEN;
+  csvConfig.channels = 1;
+  csvConfig.bits_per_sample = 16;
+  serial_out.begin(csvConfig);
+}
+
+
+void loop() {
+
+  // Read the values from the ADC buffer to local buffer
+  size_t bytes_read   = analog_in.readBytes((uint8_t*) buffer, BUFFER_SIZE * BYTES_PER_SAMPLE); // read byte stream and  cast to destination type
+  size_t samples_read = bytes_read/BYTES_PER_SAMPLE; 
+  size_t avg_samples  = samples_read/AVG_LEN;
+
+  // Average the samples over AVG_LEN
+  int32_t sum; // register to hold summed values
+  int16_t *sample = (int16_t*) buffer; // sample pointer (input)
+  int16_t *avg = (int16_t*) buffer; // result pointer (output)
+  // each time we access a sample we increment sample pointer
+  for(uint16_t j=0; j<avg_samples; j++){
+    sum = *sample++; // initialize sum
+    for (uint16_t i=1; i<AVG_LEN; i++){
+      sum += *sample++; // sum the samples
+    }
+    // compute average and store in output buffer
+    *avg++ = (int16_t) (sum/AVG_LEN); 
+  }
+
+  serial_out.write((uint8_t*)buffer, avg_samples*BYTES_PER_SAMPLE); // stream to output as byte type
+}