STM32F4Discovery board is already quite powerful and stacked with many handy features. You can find a three-axis accelerometer, MEMS microphone, DAC with D class amplifier that can output sound through the built-in audio jack on a single board. Also, there are a couple of LEDs and a button for fast access. Of course, this board’s core is the STM32F407VGT6 ARM Cortex-M4 microcontroller that packs a series of great features, including DSP instructions and a floating-point unit. But eventually, with such power, you will miss several other handy features that could be used in your project. Think of LCD, Ethernet, RS232 interface, and even camera. You could start making your extension boards that include additional features, but why bother since several extension boards are available for it. Let us go through them and see the features you could get without a heating soldering iron.