【ARM】ARM裸板编程之GPIO(LED二)

00. 目录

01. 控制原理

咱们的LED在核心板上，所以需要看核心板的原理图

打开核心板原理图(Tiny4412-1412-Schematic.pdf)

由上图可知，Tiny4412有4个用户LED灯，控制它们四个引脚分别是GPM4_0~ GPM4_3，由原理可知，当IO引脚为高电平时，LED灯灭，当IO引脚为低电平时LED亮。我们要做的工作就是设置GPM4_0~ GPM4_3为输出功能，且控制且输出电平高低即可。

02. 配置寄存器

由原理图可知，程序只进行了两步操作。

第一步：设置GPM4_0~GPM4_3相对应的控制寄存器GPM4CON，使GPM4_0 GPM4_3四个引脚为输出功能。

第二步：设置其对应的数据寄存器GPM4DAT对应的4个bit位为0，使GPM4_0~ GPM4_3为低电平，4个LED灯全亮，使GPM4_0~ GPM4_3全为高电平，4个LED灯全灭。

03. 程序示例一

所有led闪烁 汇编函数

    .section .rodata
    .align 2
.LC0:
    .string "led all off\n"


    .section .text
    .align 2
    .global _start
_start:
    stmfd sp!, {lr}

    bl led_init
1:
    bl led_alloff

    ldr r0, =1000000
    bl led_delay

    bl led_allon

    ldr r0, =1000000
    bl led_delay

    b 1b
  
    ldmfd sp!, {pc}

    .align 2
    .global led_init
led_init:
    @配置为输出
    ldr r0, =0x110002E0  
    ldr r1, [r0]
    ldr r2, =0xffff
    bic r1, r1, r2

    ldr r2, =0x1111
    orr r1, r1, r2
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_allon
led_allon:
    ldr r0, =0x110002E4    
    ldr r1, [r0]
    bic r1, r1, #0xf
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_alloff
led_alloff:
    ldr r0, =0x110002E4    
    ldr r1, [r0]
    orr r1, r1, #0xf
    str r1, [r0]
    mov pc, lr


    .align 2
    .global led_delay
led_delay:
    stmfd sp!, {lr}

    mov lr, pc
    ldr pc, =0x43e26480

    ldmfd sp!, {pc}

Makefile

all:
	arm-linux-gcc -c test.s -o test.o
	arm-linux-ld -Ttext=0x40008000 test.o -o test
	arm-linux-objcopy -O binary test test.bin

.PHONY:clean
clean:
	rm -rf test.o test test.bin

04. 程序示例二

所有led闪烁 汇编函数 多文件操作

lib.s文件内容如下

    .section .text
    .align 2
    .global led_delay
led_delay:
    stmfd sp!, {lr}

    mov lr, pc
    ldr pc, =0x43e26480

    ldmfd sp!, {pc}

led.s文件内容如下

    .section .text
    .align 2
    .global led_init
led_init:
    @配置为输出
    ldr r0, =0x110002E0  
    ldr r1, [r0]
    ldr r2, =0xffff
    bic r1, r1, r2

    ldr r2, =0x1111
    orr r1, r1, r2
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_allon
led_allon:
    ldr r0, =0x110002E4    
    ldr r1, [r0]
    bic r1, r1, #0xf
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_alloff
led_alloff:
    ldr r0, =0x110002E4    
    ldr r1, [r0]
    orr r1, r1, #0xf
    str r1, [r0]
    mov pc, lr

test.s文件内容如下:

    .section .rodata
    .align 2
.LC0:
    .string "led all off\n"


    .section .text
    .align 2
    .global _start
_start:
    stmfd sp!, {lr}

    bl led_init
1:
    bl led_alloff

    ldr r0, =1000000
    bl led_delay

    bl led_allon

    ldr r0, =1000000
    bl led_delay

    b 1b

    
    ldmfd sp!, {pc}

Makefile文件

all:
	arm-linux-gcc -c test.s -o test.o
	arm-linux-gcc -c led.s -o led.o
	arm-linux-gcc -c lib.s -o lib.o
	arm-linux-ld -Ttext=0x40000000 test.o lib.o led.o  -o test
	arm-linux-objcopy -O binary test test.bin


.PHONY:clean
clean:
	rm -rf *.o test test.bin

05. 程序示例三

跑马灯程序

lib.s文件内容

     .align 2
    .global led_delay
led_delay:
    stmfd sp!, {lr}

    mov lr, pc
    ldr pc, =0x43e26480

    ldmfd sp!, {pc}

led.s文件内容

    .section .text
    .align 2
    .global led_init
led_init:
    @配置为输出
    ldr r0, =0x110002E0  
    ldr r1, [r0]
    ldr r2, =0xffff
    bic r1, r1, r2

    ldr r2, =0x1111
    orr r1, r1, r2
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_allon
led_allon:
    ldr r0, =0x110002E4    
    ldr r1, [r0]
    bic r1, r1, #0xf
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_alloff
led_alloff:
    ldr r0, =0x110002E4    
    ldr r1, [r0]
    orr r1, r1, #0xf
    str r1, [r0]
    mov pc, lr

    .align 2
    .global led_on
led_on:
    ldr r1, =0x110002E4    
    ldr r2, [r1]
    mov r3, #1
    bic r2, r2, r3, LSL r0
    str r2, [r1]

    mov pc, lr


    .align 2
    .global led_off
led_off:
    ldr r1, =0x110002E4    
    ldr r2, [r1]
    mov r3, #1
    orr r2, r2, r3, LSL r0
    str r2, [r1]

    mov pc, lr

test.s文件内容

    .section .rodata
    .align 2
.LC0:
    .string "led all off\n"


    .section .text
    .align 2
    .global _start
_start:
    stmfd sp!, {lr}

    bl led_init
    bl led_alloff

    mov r4, #0

1:
    mov r0, r4
    bl led_on


    ldr r0, =1000000
    bl led_delay

    mov r0, r4
    bl led_off

    ldr r0, =1000000
    bl led_delay

    add r4, r4, #1
    cmp r4, #4
    moveq r4, #0

    b 1b
    
    ldmfd sp!, {pc}

Makefile文件

all:
	arm-linux-gcc -c test.s -o test.o
	arm-linux-gcc -c led.s -o led.o
	arm-linux-gcc -c lib.s -o lib.o
	arm-linux-ld -Ttext=0x40000000 test.o lib.o led.o  -o test
	arm-linux-objcopy -O binary test test.bin


.PHONY:clean
clean:
	rm -rf *.o test test.bin

06. 附录

Exynos 4412 SCP_Users Manual_Ver.0.10.00_Preliminary0.pdf