Before I made a audio level / waveform display embedded class-D amplifier. This time, this part is separated and added LiPo charging circuit. Together with small LiPo battery (3.7 V, 280mAh), this tiny audio level meter provides portable small joy to your music listening!
The above circuit shows the total of this tiny audio level meter. Audio level detection is solely by A/D in Atmega 328p. As same as my all making, Arduino bootloader (Arduino Pro) is preloaded and its firmware is re-writable by USB-TTL interface with DTR/TX/RX.
Just sampling audio signal and biased up to VDD/2 and injected in A0/A1 of atmega 328p. The actual operation can be found in the following movie... have fun!