嵌入式 linux 驱动 ADＣ驱动

很懒，很久没去总结学习的东西，今天就总结下ｌｉｎｕｘ下的ＡＤ驱动吧，ＡＤ驱动理解的难点和注意的地方其实就只有两点。

一、虚拟地址的应用，就是物理地址转换为虚拟地址，ＡＤＣ驱动程序中的寄存器就是都用到了虚拟地址了。其中最主要的转换的语句是

base_addr=ioremap(S3C2410_PA_ADC,0x20);/

ioremap（）功能：将一个IO地址空间映射到内核的虚拟地址空间上去，返回值就是虚拟地址。物理地址和虚拟地址的转换，就是将S3C2410_PA_ADC物理地址转换为base_addr 的地址。 S3C2410_PA_ADC 为物理地址0x58000000 ，具体也不知在那个文件能找到。base_addr 虚拟地址，应该是有系统分配的，调用ioremap()既能分配到。

而base_addr 的定义是　static void __iomem *base_addr;

使用完后需要 iounmap(base_addr);释放掉虚拟地址。

二、时钟CLK的调用，用ADC需要用到CLK时钟，主要有已下几个函数：

clk_get
clk_use()
clk_enable()

这几个函数的使用，当然再最后也要卸载掉，其函数如下

  clk_disable(adc_clock);
  clk_put(adc_clock);
  adc_clock = NULL;
}

还有可以参考如下网页

http://www.unixresources.net/linux/clf/driver/archive/00/00/65/81/658138.html

http://hi.baidu.com/mystreetzone/blog/item/f36fca35d373001690ef39a7.html

最后附上具体程序
＃i nclude <linux/errno.h>
＃i nclude <linux/kernel.h>
＃i nclude <linux/module.h>
＃i nclude <linux/slab.h>
＃i nclude <linux/input.h>
＃i nclude <linux/init.h>
＃i nclude <linux/serio.h>
＃i nclude <linux/delay.h>
＃i nclude <linux/clk.h>
＃i nclude <asm/io.h>
＃i nclude <asm/irq.h>
＃i nclude <asm/uaccess.h>
＃i nclude <mach/regs-clock.h>
＃i nclude <plat/regs-timer.h>

＃i nclude <plat/regs-adc.h>
＃i nclude <mach/regs-gpio.h>
＃i nclude <linux/cdev.h>
＃i nclude <linux/miscdevice.h>

＃i nclude "s3c24xx-adc.h"

#undef DEBUG
//#define DEBUG
#ifdef DEBUG
#define DPRINTK(x...) {printk(____"(%d): ",__LINE__);printk(##x);}
#else
#define DPRINTK(x...) (void)(0)
#endif

#define DEVICE_NAME "adc"

static void __iomem *base_addr;

typedef struct {
wait_queue_head_t wait;
int channel;
int prescale;
}ADC_DEV;

DECLARE_MUTEX(ADC_LOCK);
static int OwnADC = 0;

static ADC_DEV adcdev;
static volatile int ev_adc = 0;
static int adc_data;

static struct clk *adc_clock;

#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)

#define START_ADC_AIN(ch, prescale) \
do{ \
ADCCON = PRESCALE_EN | PRSCVL(prescale) | ADC_INPUT((ch)) ; \
ADCCON |= ADC_START; \
}while(0)

static irqreturn_t adcdone_int_handler(int irq, void *dev_id)
{
if (OwnADC) {
adc_data = ADCDAT0 & 0x3ff;

ev_adc = 1;
wake_up_interruptible(&adcdev.wait);
}

return IRQ_HANDLED;
}

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;
if (down_trylock(&ADC_LOCK) == 0) {
  OwnADC = 1;
  START_ADC_AIN(adcdev.channel, adcdev.prescale);
  wait_event_interruptible(adcdev.wait, ev_adc);

ev_adc = 0;

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

  value = adc_data;
  sprintf(str,"%5d", adc_data);
  copy_to_user(buffer, (char *)&adc_data, sizeof(adc_data));

  OwnADC = 0;
  up(&ADC_LOCK);
} else {
  value = -1;
}

len = sprintf(str, "%d\n", value);
if (count >= len) {
  int r = copy_to_user(buffer, str, len);
  return r ? r : len;
} else {
  return -EINVAL;
}
}

static int s3c2410_adc_open(struct inode *inode, struct file *filp)
{
init_waitqueue_head(&(adcdev.wait));

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);//功能：将一个IO地址空间映射到内核的虚拟地址空间上去，便于访问；
/*
  物理地址和虚拟地址的转换，就是将S3C2410_PA_ADC物理地址转换为base_addr 的地址
  S3C2410_PA_ADC 为物理地址0x58000000 ，具体也不知在那个文件能找到
  base_addr 虚拟地址，应该是有系统分配的，调用ioremap()既能分配到

*/
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);
//用AD 需要打开CLK
//既需要这两个函数clk_get() 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);
}

EXPORT_SYMBOL(ADC_LOCK);
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("FriendlyARM Inc.");

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嵌入式 linux 驱动 ADＣ驱动

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