微處理器 - Broadcom BCM2835 (Raspberry Pi) - Assembly - Button

參考資料：
https://elinux.org/RPi_Software#ARM
https://github.com/dwelch67/raspberrypi
https://github.com/raspberrypi/firmware
https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf

Button連接到GPIO-31


暫存器


Alternate Function


提昇電阻設定



main.s

    .global _start

    .equiv GPFSEL2,   0x20200008
    .equiv GPFSEL3,   0x2020000c
    .equiv GPSET0,    0x2020001c
    .equiv GPCLR0,    0x20200028
    .equiv GPLEV0,    0x20200034
    .equiv GPPUD,     0x20200094
    .equiv GPPUDCLK0, 0x20200098

    .arm
    .text
_start:
    b reset
    b .
    b .
    b .
    b .
    b .
    b .
    b .
         
reset:
    ldr r0, =GPFSEL2
    ldr r1, =(1 << 27)
    str r1, [r0]

    ldr r0, =GPFSEL3
    ldr r1, =0x00000000
    str r1, [r0]

    ldr r0, =GPPUD
    ldr r1, =0x02
    str r1, [r0]

    ldr r0, =GPPUDCLK0
    ldr r1, =(1 << 31)
    str r1, [r0]

0:
    ldr r0, =GPLEV0
    ldr r1, [r0]
    and r1, #(1 << 31)
    cmp r1, #0
    ldrne r0, =GPSET0
    ldreq r0, =GPCLR0
    ldr r1, =(1 << 29)
    str r1, [r0]
    b 0b
    .end

完成