You chose fpga when you have yo handle bit streams with a precise clock to interface with a hardware, for example a screen or camera. It is very difficult to h

You chose fpga when you have yo handle bit streams with a precise clock to interface with a hardware, for example a screen or camera. It is very difficult to have a precise timing with a microcontroller unless you have a good one with timers. It becomes impossible to do when you need to toggle several pins at the same time quickly (like a pci bus). You overcome the problem by adding a fpga to your microcontroller board, which will handle the bit flipping and communicate to the micro with a standard bus like spi or i2c.