Maple Mini with DMA ADC and SPI OLED display

Maple Mini demo, STM32F103RCBT6 32bit MCU running at 72MHz with 20KB of RAM. Double-buffered display code running my own 3D library updating the screen at 60Hz via a timer interrupt. Running an slightly optimized FFT routine (2.6ms processing time) with 256 samples. ADC capture is via DMA at about 42kHz sampling rate. Audio samples are double buffered as well, with the live data updating the audio backbuffer. 3D code shows two counter-rotating cubes, and the floating point operations to do the 3D consume most of the CPU cycles at the moment.