I am a begginer. I want to make a integrated system with a microcontroller which will read the pins of an other microcontroller and can send him input signals too.I want my microcontroller to have usb support as he will communicate with the computer via usb.Can you suggest me a processor(preferably avr family or arm) or what features of the microprocessor should i look for so that my system is fast and functional as i have to control 40 pins (for example) of the other microprocessor ?
I also have a question. Why do various programmers use microcontrollers that they do not support usb?(I have an arduino with atmega328p which i noticed doesn't support usb)