This repository contains the source code to the firmware for a 48kHz 16-bit USB microphone implemented using an I2S INMP441 MEMS microphone and an STM32F446.
Additional features include real-time graphic equalizer and smart volume control audio processing using ST Micro's GREQ and SVC libraries.
The documentation for this project can be found at my website.
The firmware has been tested to build successfully on Ubuntu Linux and it should work on any similar system. You'll need to have the arm-none-eabi gcc toolchain installed. If you haven't got this then Google 'arm-none-eabi' for instructions how to install it.
If you also want to flash the firmware to a device over an SWD connection managed by ST-Link then you'll also need the STM32CubeProgrammer package. Again, if you haven't got it then Google it and follow the online installation instructions. When installing on a Linux system then do it from an elevated sudo prompt so that it gets installed into /usr/local/STMicroelectronics/STM32Cube/STM32CubeProgrammer.
A Makefile is provided that will build the firmware and optionally flash it. Here are example invocations:
make release ; builds an optimised binary with -O3
make debug ; builds a debug binary with -O0 -g3
If you also want to automatically flash the firmware using a connected ST-Link debugger then just append the flash target.
make release flash
make debug flash
The flash target assumes that you've installed STM32CubeProgrammer into /usr/local/STMicroelectronics/STM32Cube/STM32CubeProgrammer. If this is not the case then edit Makefile and correct the PROGRAMMER macro at the top of the file.
All generated files are placed in a build subdirectory.
If you'd like to edit the firmware in the STM32Cube IDE then .project and .cproject files are provided that can be imported directly into the IDE.
You will find Debug and Debug_Semihosting build configurations that use standard GDB debugging and debugging with semihosting enabled, respectively. There are matching Debug and Debug_Semihosting launch configurations to use for live hardware debugging. I don't keep semihosting enabled all the time because it's just so dreadfully slow.
The CubeMX GUI configuration file usb-microphone.ioc is provided for reference only. You can open and view it but don't try to generate project source code from it because the sources have diverged so much from what CubeMX expects that it will overwrite the firmware source.
In the wav-samples directory you'll find some sample audio files:
1-direct-no-transforms.wav: Straight from the microphone, no processing. It's very quiet.
2-svc-36db-amplification.wav: 36dB amplification applied by the SVC filter.
3-svc-greq.wav: -6 -6 -6 +6 +6 +6 +6 +6 +6 +6 GREQ filter followed by +36dB SVC filter.