本章节接着上一章
编程环境搭建:
开发板:野火Imx6ull mini板
编程环境:Ubuntu18.04 + VScode
开始进入代码内容：
C语言需要运行起来，少不了汇编准备好运行的环境。
汇编代码start.S如下:
.global _start @全局标号 _start : mrs r0, cpsr @拷贝CPSR状态寄存器到R0中 bic r0, r0, #0x1f @清楚CPU模式位BIT4-BIT0 orr r0, r0, #0x13 @配置BIT4-0为SVC模式 msr cpsr, r0 @将寄存器R0数据写回到CPSR中 ldr sp, =0x80200000 @设置堆栈0x80200000->0x80000000 2M空间 b main @跳转到C语言main函数
有了上述代码，就能和stm32一样写代码了。
C代码部分来个头文件led.h，将CPU相关寄存器地址指针给定义出来:
#ifndef _H_LED_H #define _H_LED_H #define CCM_CCGR0 *((volatile unsigned int *)0x020c4068) #define CCM_CCGR1 *((volatile unsigned int *)0x020c406C) #define CCM_CCGR2 *((volatile unsigned int *)0x020c4070) #define CCM_CCGR3 *((volatile unsigned int *)0x020c4074) #define CCM_CCGR4 *((volatile unsigned int *)0x020c4078) #define CCM_CCGR5 *((volatile unsigned int *)0x020c407C) #define CCM_CCGR6 *((volatile unsigned int *)0x020c4080) #define SW_MUX_GPIO5_IO3 *((volatile unsigned int *)0x02290014) #define SW_PAD_GPIO5_IO3 *((volatile unsigned int *)0x02290058) #define GPIO5_DR *((volatile unsigned int *)0x020AC000) #define GPIO5_GDIR *((volatile unsigned int *)0x020AC004) #define LED_ON() (GPIO5_DR &= ~(1<<3)) #define LED_OFF() (GPIO5_DR |= (1<<3)) #endif // !_H_LED_H
可执行代码片段:
#include "led.h"
void clk_enable(void)
{
CCM_CCGR0 = 0xffffffff ;
CCM_CCGR1 = 0xffffffff ;
CCM_CCGR2 = 0xffffffff ;
CCM_CCGR3 = 0xffffffff ;
CCM_CCGR4 = 0xffffffff ;
CCM_CCGR5 = 0xffffffff ;
CCM_CCGR6 = 0xffffffff ;
}
void led_Init(void)
{
SW_MUX_GPIO5_IO3 = 0x5; //AL5
SW_PAD_GPIO5_IO3 = 0x08B0;
GPIO5_GDIR = 0x08;
LED_ON() ;
}
void delay_ms(volatile unsigned int nms)
{
unsigned int nus;
while(nms--)
{
//1 ms延时
nus=0x7ff;
while(nus--)
{
}
}
}
int main(void)
{
clk_enable(); //使能时钟
led_Init(); //初始化led灯
//led闪烁循环
while(1)
{
LED_OFF();
delay_ms(500);
LED_ON();
delay_ms(500);
}
return 0;
}
代码部分好了，接下来准备一下链接脚本，用于指定编译程序起始地址和顺序
SECTIONS{
. = 0x87800000;
.text :
{
start.o
led.o
*(.text)
}
.rodata ALIGN(4) : {*(.rodata*)}
.data ALIGN(4) : { *(.data) }
__bss_start = .;
.bss ALIGN(4) : { *(.bss) *(COMMON)}
__bss_end = .;
}
准备Makefile进行起飞编译吧：
objs := start.o led.o led.bin : $(objs) arm-linux-gnueabihf-ld -Timxu.lds -o led.elf $^ arm-linux-gnueabihf-objcopy -O binary -S led.elf $@ %.o : %.s arm-linux-gnueabihf-gcc -Wall -nostdlib -c -o $@ $< %.o : %.S arm-linux-gnueabihf-gcc -Wall -nostdlib -c -o $@ $< %.o : %.c arm-linux-gnueabihf-gcc -Wall -nostdlib -c -o $@ $< clean: rm -rf *.o led.bin led.elf led.dis *.imx dump: arm-linux-gnueabihf-objdump -D -m arm led.elf > led.dis dowmload: ./imxdownload led.bin /dev/sdb
试试编译效果:
motiongui@motiongui-VirtualBox:~/work/imxAss/Ledc$ make arm-linux-gnueabihf-gcc -Wall -nostdlib -c -o start.o start.S arm-linux-gnueabihf-gcc -Wall -nostdlib -c -o led.o led.c arm-linux-gnueabihf-ld -Timxu.lds -o led.elf start.o led.o arm-linux-gnueabihf-objcopy -O binary -S led.elf led.bin
