（14）mini2440之ADC驱动

（14）mini2440之ADC驱动

 

注：所以文章红色字体代表需要特别注意和有问题还未解决的地方，蓝色字体表示需要注意的地方

1.本文所介绍的程序平台

开发板：arm9-mini2440

虚拟机为：Red Hat Enterprise Linux 5

开发板上系统内核版本：linux-2.6.32.2

 

2.程序清单

本次实验程序为网络代码，本人作了改动和较为详细的注释，如有错误请指出。

 

s3c24xx-adc.h

 

#ifndef _S3C2410_ADC_H_

#define _S3C2410_ADC_H_ 

#define ADC_WRITE_GETCH(data)    (((data)>>16)&0x7)

#define ADC_WRITE_GETPRE(data)    ((data)&0xff)

// ADC_WRITE_GETCH(data)得到ch ADC_WRITE_GETPRE(data)得到prescale！！

#define ADC_WRITE(ch, prescale)    ((ch)<<16|(prescale))

#endif                          /* _S3C2410_ADC_H_ */

 

mini2440_adc.c

 

/*ADC驱动 ,其头文件作用还未明白??*/

#include

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#include

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//自己定义的头文件 因为原生内核并么有包含

#include "s3c24xx-adc.h"

 

#undef DEBUG

//#define DEBUG

#ifdef DEBUG

#define DPRINTK(x...) {printk(__FUNCTION__"(%d): ",__LINE__);printk(##x);}

#else

#define DPRINTK(x...) (void)(0)

#endif

 

#define DEVICE_NAME "adc"

 

static void __iomem *base_addr;

 

//定义ADC设备就结构

typedef struct {

    wait_queue_head_t wait;

    int channel;

    int prescale;

}ADC_DEV;

 

//声明全局变量,以使和触摸屏驱动程序共享A/D转换器

DECLARE_MUTEX(ADC_LOCK);

 

//ADC驱动是否拥有A/D转换器资源的状态变量

static int OwnADC = 0;

 

static ADC_DEV adcdev;

static volatile int ev_adc = 0;

static int adc_data;

 

static struct clk   *adc_clock;

 

//定义ADC相关的寄存器

#define ADCCON      (*(volatile unsigned long *)(base_addr + S3C2410_ADCCON))    //ADC control

#define ADCTSC      (*(volatile unsigned long *)(base_addr + S3C2410_ADCTSC))    //ADC touch screen control

#define ADCDLY      (*(volatile unsigned long *)(base_addr + S3C2410_ADCDLY))    //ADC start or Interval Delay

#define ADCDAT0     (*(volatile unsigned long *)(base_addr + S3C2410_ADCDAT0))   //ADC conversion data 0

#define ADCDAT1     (*(volatile unsigned long *)(base_addr + S3C2410_ADCDAT1))   //ADC conversion data 1

#define ADCUPDN     (*(volatile unsigned long *)(base_addr + 0x14))  //Stylus Up/Down interrupt status

 

#define PRESCALE_DIS        (0 << 14)

#define PRESCALE_EN         (1 << 14)

#define PRSCVL(x)           ((x) << 6)

#define ADC_INPUT(x)        ((x) << 3)

#define ADC_START           (1 << 0)

#define ADC_ENDCVT          (1 << 15)

 

//开启AD输入

#define START_ADC_AIN(ch, prescale) \

    do{ \

        ADCCON = PRESCALE_EN | PRSCVL(prescale) | ADC_INPUT((ch)) ; \

        ADCCON |= ADC_START; \

    }while(0)

 

 

//ADC中断处理函数

static irqreturn_t adcdone_int_handler(int irq, void *dev_id)

{

    //如果ADC驱动拥有A/D转换器资源，则从ADC寄存器读取转换状态

    if (OwnADC) {

        adc_data = ADCDAT0 & 0x3ff;

        ev_adc = 1;

        wake_up_interruptible(&adcdev.wait);

    }

 

    return IRQ_HANDLED;

}

 

//ADC读函数,

static ssize_t s3c2410_adc_read(struct file *filp, char *buffer, size_t count, loff_t *ppos)

{

    char str[20];

    int value;

    size_t len;

 

    //判断'A/D转换器'资源是否可用

    if (down_trylock(&ADC_LOCK) == 0) {

        OwnADC = 1;//标记为'A/D转换器'资源是可用

        START_ADC_AIN(adcdev.channel, adcdev.prescale);//开始转换

        wait_event_interruptible(adcdev.wait, ev_adc);//等待转换结束

 

        ev_adc = 0;

 

        DPRINTK("AIN[%d] = 0x%04x, %d\n", adcdev.channel, adc_data, ADCCON & 0x80 ? 1:0);

 

        //把转换结果赋值,以便传递到用户层

        value = adc_data;

 

        //释放A/D转换器资源

        OwnADC = 0;

        up(&ADC_LOCK);

       

    } else {

        //没有A/D转换器资源

        value = -1;

    }

 

    len = sprintf(str, "%d\n", value);

    if (count >= len) {

        //将转换结果传到到用户层

        int r = copy_to_user(buffer, str, len);

        return r ? r : len;

    } else {

        return -EINVAL;

    }

}

 

//ADC设备的打开函数

static int s3c2410_adc_open(struct inode *inode, struct file *filp)

{

    //初始化中断队列

    init_waitqueue_head(&(adcdev.wait));

 

    //缺省通道为'0'

    adcdev.channel=0;

    adcdev.prescale=0xff;

 

    DPRINTK( "adc opened\n");

    return 0;

}

 

static int s3c2410_adc_release(struct inode *inode, struct file *filp)

{

    DPRINTK( "adc closed\n");

    return 0;

}

 

 

static struct file_operations dev_fops = {

    owner:  THIS_MODULE,

    open:   s3c2410_adc_open,

    read:   s3c2410_adc_read,  

    release:    s3c2410_adc_release,

};

 

static struct miscdevice misc = {

    .minor = MISC_DYNAMIC_MINOR,

    .name = DEVICE_NAME,

    .fops = &dev_fops,

};

 

static int __init dev_init(void)

{

    int ret;

 

    base_addr=ioremap(S3C2410_PA_ADC,0x20);

    if (base_addr == NULL) {

        printk(KERN_ERR "Failed to remap register block\n");

        return -ENOMEM;

    }

 

    adc_clock = clk_get(NULL, "adc");

    if (!adc_clock) {

        printk(KERN_ERR "failed to get adc clock source\n");

        return -ENOENT;

    }

    clk_enable(adc_clock);

   

    /* normal ADC */

    ADCTSC = 0;

 

    ret = request_irq(IRQ_ADC, adcdone_int_handler, IRQF_SHARED, DEVICE_NAME, &adcdev);

    if (ret) {

        iounmap(base_addr);

        return ret;

    }

 

    ret = misc_register(&misc);

 

    printk (DEVICE_NAME"\tinitialized\n");

    return ret;

}

 

static void __exit dev_exit(void)

{

    free_irq(IRQ_ADC, &adcdev);

    iounmap(base_addr);

 

    if (adc_clock) {

        clk_disable(adc_clock);

        clk_put(adc_clock);

        adc_clock = NULL;

    }

 

    misc_deregister(&misc);

}

 

//导出信号量"ADC_LOCK"以便触摸屏驱动使用

EXPORT_SYMBOL(ADC_LOCK);

module_init(dev_init);

module_exit(dev_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("FriendlyARM Inc.");