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libraries/audio-tools/examples/examples-basic-api/base-adc-measure/README.md

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+# ESP32 Analog to Digital Conversion Throughput using Continuous ADC API
+
+Data is reported in bytes per second when using a single ADC unit and two A/D channels.
+When each channel is measured with 4,000 samples per second the ADC is running at 8,000 samples per second as it multiplexes between the two channels.
+
+The maximum sampling frequency depends on the ESP32 model.
+
+The older ESP32 models can convert up to 2 Million samples per second, however there is discrepancy between the expected and effective throughput of about 20%.
+
+The library creates int16_t datatype which is 2 bytes per sample.
+
+## Adafruit Feather ESP32-S3 2MB PSRAM
+```
+    
+   SPS  :  expected,  measured
+      150: error, sample rate eff: 300, range: 611 to 83,333
+      306:    1,224,     1,000
+    4,000:   16,000,    16,000
+    8,000:   32,000,    32,000   
+   11,025:   44,100,    44,000
+   16,000:   64,000,    64,000
+   20,000:   80,000,    80,000
+   22,050:   88,200,    89,000
+   40,000:  160,000,   161,000
+   44,100: error, sample rate eff: 88,200, range: 611 to 83,333
+```
+
+## Sparkfun ESP32 WROOM Plus C
+```
+  Data: bytes per second, single unit, two channels
+   SPS/CH  expected,  measured % of expected
+    5000:  error, sample rate eff: 10000, range: 20000 to 2000000
+   10000:    40,000,    32,000
+   22050:    88,200,    72,000
+   44100:   176,400,   144,000
+   88200:   352,800,   157,000
+  500000: 2,000,000, 1,635,000
+ 1000000: 4,000,000, 3,271,000
+```
+
+## DOIT ESP32 DEVKIT V1
+```
+  Data: bytes per second, single unit, two channels
+   SPS  :  expected,  measured 80% of expected
+    5000:  error, sample rate: 5000, range: 10000 to 1000000
+   10000:    40,000,    32,000
+   20000:    80,000,    64,000
+   22050:    88,200,    72,000
+   44100:   176,400,   144,000
+   48000:   192,000,   156,000
+   88200:   352,800,   288,000
+   96000:   384,000,   313,000
+  176400:   705,600,   576,000
+  192200:   768,800,   628,000
+  352800: 1,411,200, 1,153,000
+  384000: 1,536,000, 1,256,000
+  500000: 2,000,000, 1,635,000
+ 1000000: 4,000,000, 3,271,000
+ 1500000: error, sample rate: 1500000, range: 10000 to 1000000
+```

libraries/audio-tools/examples/examples-basic-api/base-adc-measure/base-adc-measure.ino

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+/**
+ * Internal ADC: It depdens pretty much on our processor & arduino version if and how
+ * this is supported.
+ */
+
+#include "Arduino.h"
+#include "AudioTools.h"
+
+// On board analog to digital converter
+AnalogAudioStream analog_in; 
+
+// Measure throughput
+MeasuringStream measure(1000, &Serial);
+
+// Copy input to output
+StreamCopy copier(measure, analog_in);
+
+void setup() {
+
+  delay(3000); // wait for serial to become available
+
+  // Serial Interface
+  Serial.begin(115200);
+  // Include logging to serial
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Info); //Warning, Info, Error, Debug
+  
+  // Configure ADC input
+  auto adcConfig = analog_in.defaultConfig(RX_MODE);
+
+  // For ESP32 by Espressif Systems version 3.0.0 and later 
+  // see examples/README_ESP32.md
+  // adcConfig.sample_rate = 22050;
+  // 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 = 2;
+  // adcConfig.adc_channels[0] = ADC_CHANNEL_4; 
+  // adcConfig.adc_channels[1] = ADC_CHANNEL_5;
+
+  adcConfig.sample_rate = 44100; // per channel
+
+  Serial.println("Starting ADC...");
+  analog_in.begin(adcConfig);
+
+  // Start Measurements
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning); //Warning, Debug, Info, Error
+  Serial.println("Starting through put measurement...");
+}
+
+void loop() {
+  copier.copy(); 
+}