ak3-labs-asm/start.S

.syntax unified
.cpu cortex-m4
.thumb

.equ SYSTICK_OFFSET, 0xE000E010
.equ RCC_OFFSET, 0x40023800
.equ GPIOD_OFFSET, 0x40020C00

.section .text

vtable:
    .word __stack_start
    .word __hard_reset__+1
    .align 2
v2_img_start:
    .incbin "lab1_v2.bin"
    .align 2
v2_img_end: @ ==__hard_reset__

__hard_reset__:
    bl setup_leds
    bl load_systick_timer
    bl lab1_v1

    bl bootload_v2

    readloop:
    ldr.n r0, [r7, #8]
    wfi
    b.n readloop

load_systick_timer:
    @ SysTick_LOAD
    ldr.n r7, =SYSTICK_OFFSET
    mov r1, #0x1
    lsl r1, #20
    str.n r1, [r7, #4]

    @ SysTick_CTRL
    mov r1, #0x1
    str.n r1, [r7]

    mov pc, lr

bootload_v2:
    push {lr}

    @ bootload to ram
    ldr.n r0, =v2_img_start
    ldr.n r1, =v2_img_end
    ldr.n r3, =__ram_start

    copy_loop:
    ldr r2, [r0], #4
    str r2, [r3], #4
    cmp.n r0, r1
    bne.n copy_loop

    ldr.n r3, =__ram_start
    add r3, r3, #1

    push {r3}
    blx r3
    pop {r3}

    @ patch A
    ldr r0, =0x707ff64d @ 0xDF7F
    str r0, [r3, #0xb]

    push {r3}
    blx r3
    pop {r3}

    @ patch A and B
    ldr r0, =0x000af240 @ 0x000A
    str r0, [r3, #0xb]
    ldr r0, =0x010af240 @ 0x000A
    str r0, [r3, #0xf]

    blx r3

    pop {pc}

setup_leds:
    @ RCC reset & enable GPIOD
    ldr r0, =RCC_OFFSET
    mov r1, #0x8
    str r1, [r0, #0x30] @ ENABLE

    @ GPIOD config
    ldr r0, =GPIOD_OFFSET

    ldr r1, =0x55000000
    str r1, [r0] @ Mode Register

    mov r1, #0xF000
    str r1, [r0, #0x14] @ Output Data Register

    mov pc, lr