Converter of ZX Spectrum video signal to VGA video signal (640x480).
Dev board schematic is here: https://github.com/iliasam/stm32f429_vga_examples/blob/master/schematic/schematic_v1.1.png
http://we.easyelectronics.ru/citizen/zahvat-videosignala-ot-zx-spectrum-pri-pomoschi-stm32f4.html