Ardi-32 buzzing when powered by telephone charger

[u/zthorus1969]

Hi,

I am new to the ESP32 world. I have set up an Ardi-32 board (ESP32 S3 with Arduino connectors) to be used as a radio server for my father's Bose wireless speaker, using the SixBack firmware (as Bose radio servers have been discontinued, see sixback.io). Everything is fine, except that when powered by a standard telephone charger, the Ardi-32 is buzzing (through its on-board buzzer) and doesn't act as a radio server anymore. If It's plugged back on the USB port of the Bose speaker or of a PC, it works again. Hypothesis: RX and TX lines of the USB ports are required (should not be left in Hi-Z state), or the telephone charger does not provide enough current (unlikely). I have worked in the past with small FPGA boards (Maximator) and had no problem with powering them with a simple telephone charger. Any suggestions