At present, I am using the defective first version of the design to implement functions through flying wires, and the new version of the PCB function has not yet been verified.

2021-8-20 Rewritten the front-end polling program based on the ticker library. The program and instructions are in the attachment.

Circuit description

The function size of each component is marked on the silk screen. If you have the basic knowledge, you can directly use it as the base of the development board.

DC-DC part

• LM2596 is basically fake, just use it as 1.5A. Choose this one because it has less peripherals and is more durable.
• The microcontroller Vin uses a 0 ohm resistor and a 0.1u decoupling filter. It can be replaced by a fuse or a chip power inductor. Pay attention to the resonant frequency.
• The 5V of the LED socket and the 5V of the IIC come directly from 2596, so pay attention to the safety of the line.
• Different currents are isolated.
• I currently use a 7*7 33uh inductor and there is no big problem. The pad has also been enlarged. If I want to use a smaller one, there is no big problem. Just don't use 2812 for lighting.
• Can be connected to wifi and bluetooth without affecting the sampling accuracy.
• If you use a power amplifier above 12V, please refer to the 2596 datasheet to increase the inductor size.
• All 3.3v iic power ports are led from port 3.3 of the development board and are used for low-power sensors.

audio sampling part

* The current design does not consider saving components. The mono circuit can reduce the sampling voltage to about 0.6V (avg) when the speaker 2 is 15W. For stability, a dual-channel parallel combination was chosen . Pay attention to the withstand voltage of the mlcc capacitor* *