When [Mahesh Venkitachalam] was experimenting with maker learning for audio applications on a Raspberry Pi, he found himself trying to find a basic USB microphone. A low-cost one was easy to find, but the sound quality and directionality left much to be desired. A large, studio-quality mic would be overkill, so [Mahesh] made a decision to simply build exactly what was needed: a compact, yet premium USB microphone that he called Mico.
The sensing device is a MEMS microphone that outputs a pulse density modulated (PDM) signal. There are chips available to directly interface such a microphone to a USB port, but [Mahesh] found them tough to work with and as a result settled on something he knew already: the Raspberry Pi Pico platform. Luckily, someone had already figured out how to read out a microphone and present a USB device to a PC, so all that was needed was to put all the bits together into a convenient form factor.
The terrific thing about the Pico platform is that its main controller chip, the RP2040, is available as a separate component. [Mahesh] created a sleek little PCB that holds the RP2040 along with the MEMS microphone and a USB connector. The end result looks tidy enough that it might have come out of a mass-produced gizmo. Those don’t normally come with full schematics and source code, but the Mico does: everything is available on its GitHub page for any individual to re-use and improve.
You can judge the sound quality for yourself in the video embedded below. If you like diy USB microphones, you’re in luck: we’ve featured one based on an STM32 as well as a beautiful recreation of a studio-quality mic.