Features:
1 Based on STM32F103C8T6, sufficient performance space is reserved to facilitate the expansion of functions in the future

2 Red 2088B lattice, driven by MAX7219, easy to program

3 Standard 3.5mm audio interface, powered by USB.

4 An integrated power supply/audio interface is reserved for further DIY

5 Spectrum analysis and display based on FFT, non-level display

6 The gain can be adjusted to accommodate small signals

7 Flip through the button display, convenient to switch the position of the audio interface left and right.

Notes for welding and use:

1 J1 and J2 jumpers are used to choose whether the input signal is left channel signal or right channel signal.

2 The input voltage should not be higher than 5.5V.

3 The R8 on the board is used to adjust the gain. The maximum gain is 10.

Schematic File Designed by EasyEDA , a free online PCB software

PCB Prototype Manufactured by JLCPCB by $2 for 5 pcs

PCB Design File

The BOM list also enclosed for reference.