I have DE10-nano board.
Is Linux required to use cyclone V's HSP (ARM processor)?
Is there any way to use it without Linux?
Can I download and use NIOS ii on cyclone V?
Or is it better to use cyclone IV?
I want developing UART and 4-axis PID control algorithm.
You can ignore the HPS and just use NIOS ii on the FPGA fabric. But the whole point of the HPS is to be faster and better than NIOS ii and you also save space on the FPGA side of the cyclone V.
You can ignore the HPS completely and just treat it as a simple FPGA also if you like.