Imx6ull开发板GPIO LED汇编程序

目标：熟悉imx6ull的GPIO的基本使用，包括clock使能、gpio复用、电气属性和输入输出设置及输出高低电平等操作；熟悉ARM的内部常见寄存器及汇编的常用指令，为后面u-boot和kernel移植打好基础；

1）汇编

arm-linux-gnueabihf-gcc -g -c led.s -o led.o

-g 产生gdb调试信息

-c 编译源文件

-o 产生汇编文件

2）链接

  arm-linux-gnueabihf-ld -Ttext 0x87800000 led.o -o led.elf

  地址：外部DDR中，0x87800000

  Ttext 代码段

3）格式转换

  arm-linux-gnueabihf-objcopy -O binary -S -g led.elf led.bin

  -O 表示格式转换的目标格式

4）反汇编

  arm-linux-gnueabihf-objdump -D led.elf > led.dis

========================================================================

代码烧写

Disk /dev/sdb: 14.4 GiB, 15502147584 bytes, 30277632 sectors

Units: sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disklabel type: dos

Disk identifier: 0x00000000

Device    Boot Start      End  Sectors  Size Id Type

/dev/sdb1        8192 30277631 30269440 14.4G  c W95 FAT32 (LBA)

chmod +x ./imxdownload

./imxdownload led.bin /dev/sdb

=========================================================================

拨码开关网上拨动是1，往下拨是0

SD卡启动：裸机和u-boot启动；

10000010

EMMC启动：程序固化后，固化在EMMC内部；

10100110

代码源文件如下：

---

/*

 * gpio control led using asm:LED1_3--->low--->on;high--->off

 * version:1.0

 * Date:20211016

 * 1) enable gpio module[enable clock]

 * 2) mul gpio

 * 3) set electrical properties

 * 4) set direction and data

 * 5) loop

 */

.global _start

_start:

    /*enable gpio clock*/

    ldr r0, =0x020c4068 /*CCM_CCGR0 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]

    ldr r0, =0x020c406C /*CCM_CCGR1 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]

    ldr r0, =0x020c4070 /*CCM_CCGR2 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]

    ldr r0, =0x020c4074 /*CCM_CCGR3 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]  

    ldr r0, =0x020c4078 /*CCM_CCGR4 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]

    ldr r0, =0x020c407C /*CCM_CCGR5 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]

    ldr r0, =0x020c4080 /*CCM_CCGR6 */

    ldr r1, =0xFFFFFFFF

    str r1, [r0]

    //io mul ---> gpio

    ldr r0, =0x020e0068 /*IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 */

    ldr r1, = 0x05

    str r1, [r0]

    //set electrical properties

    ldr r0, =0x020e02F4

    ldr r1, =0x10b0

    str r1, [r0]

    //set direction and data

    ldr r0, =0x0209c004

    ldr r1, =0x00000008

    str r1, [r0]  

    ldr r0, =0x0209c000

    ldr r1, =0x0

    str r1, [r0]  

loop:

    b loop

---

Makefile 如下：

led.bin:led.s

    arm-linux-gnueabihf-gcc -g -c led.s -o led.o

    arm-linux-gnueabihf-ld -Ttext 0x87800000 led.o -o led.elf

    arm-linux-gnueabihf-objcopy -O binary -S -g led.elf led.bin

    arm-linux-gnueabihf-objdump -D led.elf > led.dis

clean:

    rm -rf *.o led.bin led.elf led.dis