Exynos4412 ADC 设备驱动开发

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具体ADC硬件知识及裸机驱动请看： Exynos4412裸机开发 —— A/D转换器

1、原理图如下：

2、相关寄存器信息

ADC_BASE 0x126C0000

ADCCON 0x0000 1<<0 | 1<<14 | 0X1<<16 | 0XFF<<6

ADCDLY 0x0008
ADCDAT 0x000C &0XFFF
CLRINTADC 0x0018
ADCMUX 0x001C

3、大体驱动编写流程如下

read()

{

1、向adc设备发送要读取的命令

ADCCON 1<<0 | 1<<14 | 0X1<<16 | 0XFF<<6

2、读取不到数据就休眠

wait_event_interruptible();

3、等待被唤醒读数据

havedata = 0；

}

adc_handler（）

{

1、清中断 ADC使用中断来通知转换数据完毕的

2、状态位置位；

havedata=1；

3、唤醒阻塞进程

wake_up()

}

probe（）

{

1、读取中断号，注册中断处理函数

2、读取寄存器的地址，ioremap

3、字符设备的操作

}

4、设备树中的节点编写

fs4412-adc{    compatible = "fs4412,adc";    reg = <0x126C0000 0x20>;    interrupt-parent = <&combiner>;    interrupts = <10 3>;};

5、驱动编写

driver.c

#include <linux/module.h>#include <linux/device.h>#include <linux/platform_device.h>#include <linux/interrupt.h>#include <linux/fs.h>#include <linux/wait.h>#include <linux/sched.h>#include <asm/uaccess.h>#include <asm/io.h>static int major = 250;static wait_queue_head_t wq;static int have_data = 0;static int adc;static struct resource *res1;static struct resource *res2;static void *adc_base;#define ADCCON 0x0000   #define ADCDLY 0x0008               #define ADCDAT 0x000C              #define CLRINTADC 0x0018#define ADCMUX 0x001Cstatic  irqreturn_t adc_handler(int irqno, void *dev){have_data = 1;printk("11111\n");/*清中断*/writel(0x12,adc_base + CLRINTADC);wake_up_interruptible(&wq);return IRQ_HANDLED;}static int adc_open (struct inode *inod, struct file *filep){return 0;}static ssize_t adc_read(struct file *filep, char __user *buf, size_t len, loff_t *pos){    writel(0x3,adc_base + ADCMUX);writel(1<<0 | 1<<14 | 0X1<<16 | 0XFF<<6 ,adc_base +ADCCON );wait_event_interruptible(wq, have_data==1);/*read data*/adc = readl(adc_base+ADCDAT)&0xfff;if(copy_to_user(buf,&adc,sizeof(int))){return -EFAULT;}have_data = 0;return len;}static  int adc_release(struct inode *inode, struct file *filep){return 0;}static struct file_operations  adc_ops ={.open = adc_open,.release = adc_release,.read = adc_read,};static int hello_probe(struct platform_device *pdev){int ret;printk("match 0k \n");res1 = platform_get_resource(pdev,IORESOURCE_IRQ, 0);  res2 = platform_get_resource(pdev,IORESOURCE_MEM, 0);    ret = request_irq(res1->start,adc_handler,IRQF_DISABLED,"adc1",NULL);      adc_base = ioremap(res2->start,res2->end-res2->start);register_chrdev( major, "adc", &adc_ops);init_waitqueue_head(&wq);return 0;}static int hello_remove(struct platform_device *pdev){free_irq(res1->start,NULL);free_irq(res2->start,NULL);unregister_chrdev( major, "adc");return 0;}static struct of_device_id adc_id[]={{.compatible = "fs4412,adc" },};static struct platform_driver hello_driver={.probe = hello_probe,.remove = hello_remove,.driver ={.name = "bigbang",.of_match_table = adc_id,},};static int hello_init(void){printk("hello_init");return platform_driver_register(&hello_driver);}static void hello_exit(void){platform_driver_unregister(&hello_driver);printk("hello_exit \n");return;}MODULE_LICENSE("GPL");module_init(hello_init);module_exit(hello_exit);

test.c

#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>main(){int fd,len;int adc;fd = open("/dev/hello",O_RDWR);if(fd<0){perror("open fail \n");return ;}while(1){read(fd,&adc,4);printf("adc%0.2f V \n",(1.8*adc)/4096);}close(fd);}

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