如何使用此公式将GPIO引脚设置为输出（ARM组件）？

Question

So basically guys, Im about to rip my hair out, I cannot grasp how to deal with this. I've been given this ( gpio_addr + (4*( GPIO_NR/10))) |= (1<<(((GPIO_NR)%10)*3)

the gpio_address in my case is the virtual base address, which is 0x3F200000 and the first GPIO number is 17. What I dont understand is, how can you divide 17 by 10 and multiply it by 4 without loosing the remainder 7?

Thanks a lot guys

Answer 1

It is very simple. Your micro has two 32 bits registers for it. Every gpio pin has its own 3 bits. First ten are in the first register, another 8 in the second. When you integer divide by ten and multiply by 4 you get the address of the register. The modulo multiple 3 gives you the position in the register. Simple math.