文档介绍：精选实验四-LED跑马灯
实验四 LED跑马灯实验
一、实验目的：
1、掌握EXYNOS 4412处理器与LED指示灯的电路原理。
2、掌握linux驱动对EXYNOS 4412 GPIO的控制原理及使用方法。
二、实 0x0 = Input 0x1 = Output 0x2 = CAM_I2C1_SDA 0x3 = CAM_GPIO[13] 0x4 = CAM_SPI1_nSS 0x5 to 0xE = Reserved 0xF = EXT_INT12[3]
0x00
GPM4CON[2]
[11:8]
RW
0x0 = Input 0x1 = Output 0x2 = CAM_I2C1_SCL 0x3 = CAM_GPIO[12] 0x4 = CAM_SPI1_CLK 0x5 to 0xE = Reserved 0xF = EXT_INT12[2]
0x00
GPM4CON[1]
[7:4]
RW
0x0 = Input 0x1 = Output 0x2 = CAM_I2C0_SDA 0x3 = CAM_GPIO[11] 0x4 to 0xE = Reserved 0xF = EXT_INT12[1]
0x00
GPM4CON[0]
[3:0]
RW
0x0 = Input 0x1 = Output 0x2 = CAM_I2C0_SCL 0x3 = CAM_GPIO[10] 0x4 to 0xE = Reserved 0xF = EXT_INT12[0]
0x00
端口M4数据存放器 GPM4DAT 0x110002E4
为准备输出或输入的数据，其值为8位[7：0]。
2、LED指示灯电路原理图
从上述原理图可以清楚地看出，通过控制GPM4-0—GPM4-3管脚的电平就可以点亮或熄灭对应发光二极管。
3、linux驱动GPIO原理
动态映射(map_desc)方式
对I/O内存的操作需按如下步骤完成:
i. 申请
struct resource *request_mem_region(unsigned long start, unsigned long len, char *name)
ii. 映射
void *ioremap(unsigned long phys_addr, unsigned long size)
iii. 访问
unsigned ioread8(void *addr)
void iowrite8(u8 value, void *addr)
iv. 释放
void iounmap(void * addr)
example:
定义
#define S3C2410_PA_IIS (0x55000000)
映射
our_card->regs = ioremap(S3C2410_PA_IIS, 0x100);
访问
readl(our_card->regs )
writel(value, our_card->regs)
静态映射(map_desc)方式—linux内核已经定义好了