Yesterday I was ask to extend my Arduino AudioTools library to support RTTTL. To be honest, I had no clue what this is, so I had to look it up: RTTTL stands for Ring Tone Text Transfer Language and was developed by Nokia to transfer ringtones to cellphones. It basically descibes the notes and durations in simple text form. My library supports different sound generators and also provides the frequencies of all notes: so all Read more
In my last Arduino AudioTools Release I have integrated a RTSP server and client. The server was using RTOS tasks for the session management und a timer for timing the audio data. I decided to make things more flexible by providing different implementations for the Server and Streamer. Here is the overview of all available classes. I added a taskless server, so that we can use it w/o RTOS. Apart from the timer based standard Read more
October 2025 I’m excited to share some significant updates to the Arduino Emulator project that make it more robust, easier to use, and better aligned with official Arduino standards. These changes represent a major step forward in cross-platform Arduino development. 🔄 Arduino Core as Official Submodule The most significant architectural change is migrating to the official Arduino Core API as a git submodule. Previously, we maintained our own fork of the Arduino Core, but now Read more
Introduction Last week, I was asking myself the question how easy or difficult it would be to publish mp3 files via a RTSP server. Quite some time ago, I have extended the Mico-RTSP-Audio project to be integrated with the AudioTools, so all I theoretically needed to do was using an AudioPlayer to send mp3 files to the server. The RTSP Server I havent looked at this functionality for years, so the first thing was Read more
I was always unhappy that just importing my Arduino Audio Tools library was using quite some PROGMEM and RAM even with an empty sketch: Sketch uses 888547 bytes (67%) of program storage space. Maximum is 1310720 bytes. Global variables use 43352 bytes (13%) of dynamic memory, leaving 284328 bytes for local variables. Maximum is 327680 bytes. The root cause for this was that I considered networking to be part of the core functionality that should Read more
The Goertzel Algorithm is an optimized Discrete Fourier Transform (DFT) that can detect defined frequencies. It can be used e.g. to identify DTMF keys. DTMF keys conist of 2 tones that can be described by the following diagram: In the Arduino Audio Tools library we can use the GoertzelStream to build a simple DTMF detector. Arduino Sketch The example can be found in the examples and I was using an AI Thinker AudioKit for testing. Read more
The ResampleStream class of the Arduino Audio Tools project provides some flexible resampling functionality both on the input and the output side. To calculate the values it just uses a simple but efficient linear interpolation. I finally managed to provide an extended ResampleStreamT resampling class that uses some alternative interpolation method implementations: Here is an overview with the advantages and disadvantages: Method Quality CPU Cost Artifacts Interpolates Sample Points Linear Low Very Low High Yes Read more
Quite some time ago, I published some blogs about the ESP32 PSRAM. I think it is about time to dig a litte deeper into the topic and look at how we can use the unadressable 4 MBytes. PSRAM and C++ STL One thing that took me by surprise when I was testing with the actual ESP32 3.2.0 core, is that you just need to switch on the PSRAM in Arduino, and the C++ STL classes Read more
In my last blog, I described you I added M4A support to my Arduino Audio Tools project and how to use it. As highlited we need to access and store the stsz size tabe to play back the audio: a typical size table contains aournd 40 – 80 kbytes, but for long audio this can get much bigger: This is not an amount of data, that you would like to have to store on a Read more
Last week I was asked, if my Arduino Audio Tools project was supporting the playback of M4A files, which it didn’t: but I thought that would be quite a good opportunity to try out Vibe Coding, since this problem space is well documented and quite established it seemed to be quite a good fit. Needless to say that at that point of time I did not know anything about M4A. So I just asked Claude Read more