AES3/EBU tech 3250 Digital Audio Output on ESP32

This library will utilize the SPI output of the ES32¹ chip to form a digital audio interface according to EBU tech 3250². The code has been testet on the LilyGO TTGO-T display³ and the ESP32 D1 R32 UNO from Wemos ⁴.

Development Environment

The code has been developed in Microsoft Visual Studio VS2019 with the Visual Micro⁵ extension but it is fully compatible with the Arduino IDE⁶. Tested with version 1.8.9 Installation of arduino IDE and the TTGO-T can be done by following the procedure described at Joen's code snippets pages³ and the development board can be bought from various sites on the internet. Visual Studio can be downloaded directly from Microsoft's homepage⁷;

Library Installation Guide

Download the library in zip format.

Arduino

Open the dropdown menu Sketch and pick Include Library, Add zip library and select the file in the dowload directory.

Board Manager

Search for ESP32 and install esp32 by Espressif Systems version 3.0.5

Visual Studio

Open AddLibrary from the task bar and install library from zip and re-scan under vMicro-General.

Pin Configuration

In the AES.h the digital audio pins are assigned and the output samplerate. Please note. The assigned samplerate is two times the audio samplerate because of the bi-phase mark encoding[¨2]. GPIO_NUM_26 is the serial data output and leave the other pins un-connected. A FrameFlag is defined to pin 17 but any pin can be used.

Output Impedance

The specification calls for a ballanced 300 Ohms or 50 Ohms un-ballanced out. The output impedance of the native pin of the ESP32 is approximately 10 Ohms so adding an external resistor of 39 Ohms in series with the pin will satisfy the requirement for impedance matching and protection of the ESP32 output

Examples

The sinetone generator can be found in the example/basic folder or in the dropdown Example list under AES3.

Testing

The sinetone generator has been tested with a FFT Analyzer⁸ on the DK-Technohogies⁹ DKT7.

ToDo List

• Channel Status

Contribution

Please contact me if you like to contribute¹⁰.

Revision

Updated Oct.10. 2024 to be compatible with esp32 by Espressif Systems version 3.0.5

Footnotes

1. API reference ESP32 ESPRESSIF. ↩

2. EBU Standard Tech 3250-E 2004. ↩

3. Application example on Joen's code snippets TTGo-T. ↩ ↩²

4. Pinout for the Wemos D1 R32 [https://bpb-ap-se2.wpmucdn.com/blogs.auckland.ac.nz/dist/9/698/files/2021/08/2_Pinout_D1_R32.png] ↩

5. Visual Micro (https://www.visualmicro.com/). ↩

6. Arduino IDE (https://www.arduino.cc/en/software). ↩

7. Visual Studio (https://visualstudio.microsoft.com/downloads). ↩

8. Fast Fourier transform (https://en.wikipedia.org/wiki/Fast_Fourier_transform). ↩

9. DK-Technologies (https://www.hansens.dk/); ↩

10. Contact: Karsten Hervoe Hansen khh@hansens.dk ↩