I am providing a Bluetooth A2DP audio library for the ESP32, which can receive audio from a Bluetooth Source (e.g. a mobile phone) and play it via the I2S API provided by the IDF framework. Unfortunately Espressif has decided to go for a completely new I2S API which means that my integration needs to be rewritten. For quite some time now, I am supporting this new API via my AudioTools library, and I was considering Read more…

So far I have always used the Arduino loop to do the audio processing with the hint, that there must not be any longer delay added to the processing. If you have some blocking functions in the loop, the solution is to run the audio in a separate task. I have added some nice concurrency C++ classes to my framework which help that we can keep the sketch quite short. Arduino Example Sketch I am Read more…

There are some DACs out there that only support 32 bits: E.g the ES9018K2M module which is sold as high end HIFI DAC. Therefore sometimes it is necessary to change the sample size e.g. from 16 to 32 bits when your codec produces 16 bits. This can be easily done with the help of the NumberFormatConverterStream class of the Arduino Audio Tools library: I2SStream i2s; // final output of decoded stream NumberFormatConverterStream fc(i2s); // write Read more…

Recently there was a discussion on how to output more then 2 channels via I2S. I2S is limited to 2 channels, but the ESP32 has 2 I2S ports, so we can output a maximum of 4 channels! Arduino Sketch I have added a small example that shows how this can be done using my AudioTools library: #include <SPI.h> #include <SD.h> #include “AudioTools.h” #include “AudioCodecs/CodecMP3Helix.h” const int chipSelect=10; AudioInfo info(44100, 2, 16); I2SStream i2s_1; // final Read more…

Mozzi brings your Arduino to life by allowing it to produce much more complex and interesting growls, sweeps and chorusing atmospherics. These sounds can be quickly and easily constructed from familiar synthesis units like oscillators, delays, filters and envelopes. Mozzi supports quite a lot of different Micro controllers, but it does not have any output method that would let you capture the audio to a stream of data, so I have added some simple integration Read more…

Arrays The best way to allocate an Array of data in the AudioTools is by using a Vector. E.g. Vector<int16_t> vector{100000}; is allocating a vector of 100’000 2 byte signed integers. RAM and PSRAM The ESP32 has a few hundred kilobytes of internal RAM, residing on the same die as the rest of the chip components. It can be insufficient for audio, so it has the ability to use up to 4 MB of external Read more…

Pure Data (or just “Pd”) is an open source visual programming language for multimedia. Pure Data is developed by Miller Puckette since 1996 and you can find it on his official website along with the official documentation and other related resources. I wanted to have the possibility to run PD patches on microcontrollers. In order to achieve this I am using the hvcc hcompiler that can translate a pd file to c and c++ code. Read more…