Raspberry Pi REMCU video tutorial is now live. This is how to easily expand hardware of a Raspberry Pi board using one dollar STM32 microcontroller and several wires.
User space C++ applications and Python scripts ran on the Raspberry will gain access to internal STM32F103 peripheral modules like DAC, ADC, GPIO and others as if these peripherals were a part of Raspberry chip without having to develop a microcontroller firmware and kernel drivers.