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libraries/audio-tools/examples/examples-stream/streams-generator-pwm/README.md

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+# PWM Output Test
+
+This is a simple basic test for the PWM output.
+
+We just send a generated sine wave to some defined pins and expect to hear some audio signal.
+
+ 
+### Output Device: Piezo Electric Element
+
+To test the output I am using a piezo electric element
+
+![DAC](https://pschatzmann.github.io/Resources/img/piezo.jpeg)
+
+You can also use some simple earphones
+
+![DAC](https://pschatzmann.github.io/Resources/img/earphones.jpg)
+
+
+It should also be possible to connect a headphone to the output pins...
+
+
+The pins depend on the Processor:
+
+
+| PIEZO   |  ESP32       | RPI Pico      | MBED         | UNO R4      |
+| --------| -------------|---------------|--------------|-------------|
+| +       |  GPIO4/GPIO5 | GPIO2/GPIO3   | GPIO2/GPIO3  | GPIO2/GPIO4 |
+| -       |  GND         | GND           | GND          | GND         |

libraries/audio-tools/examples/examples-stream/streams-generator-pwm/streams-generator-pwm.ino

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+/**
+ * @file streams-generator-pwm.ino
+ * @author Phil Schatzmann
+ * @brief see https://github.com/pschatzmann/arduino-audio-tools/blob/main/examples/examples-stream/streams-generator-pwm/README.md 
+ * @author Phil Schatzmann
+ * @copyright GPLv3
+ */
+ 
+#include "AudioTools.h"
+
+AudioInfo info(8000, 1, 16);
+SineWaveGenerator<int16_t> sineWave(32000); // subclass of SoundGenerator with max amplitude of 32000
+GeneratedSoundStream<int16_t> sound(sineWave);  // Stream generated from sine wave
+PWMAudioOutput pwm;                  
+StreamCopy copier(pwm, sound);    // copy in to out
+
+
+void setup() {
+  Serial.begin(115200);
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);  
+
+  // setup sine wave
+  sineWave.begin(info, N_B4);
+
+  // setup PWM output
+  auto config = pwm.defaultConfig();
+  config.copyFrom(info);
+  //config.resolution = 8;  // must be between 8 and 11 -> drives pwm frequency (8 is default)
+  // alternative 1
+  //config.start_pin = 3;
+  // alternative 2
+  //int pins[] = {3};
+  // alternative 3
+  //Pins pins = {3};
+  //config.setPins(pins); 
+  pwm.begin(config);
+}
+
+void loop(){
+  copier.copy();
+}