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mini6410 实现 linux adc驱动详解--muge0913版 . [复制链接]

feiyang10086

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发表于 2011-12-11 16:24 |只看该作者 |倒序浏览

mini6410 实现 linux adc驱动详解--muge0913版 .

在嵌入式学习中嵌入式linux驱动占据着十分重要的地位，它不仅牵扯到操作系统、linux内核知识，同时作为开发者你必须了解面对的硬件体系结构和工作原理。在这本人muge0913对linux ad开发做了详细的介绍。

此文章仅供技术交流请勿商用。转载请注明出处：

http://blog.csdn.net/muge0913/article/details/7059241

一、ad转换器介绍

在这里我们先从adc的工作原理出发，由浅入深的学习，对于已经掌握adc硬件知识的阅读者可跳过此部分。

adc的基础知识我们可直接参考郭天祥老师的教材，免积分下载地址：

http://download.csdn.net/detail/muge0913/3903535

二、ARM中ad转换器介绍

这里我们以arm11为例：

①简介：

.

10-bit/12-bit的CMOSADC（模数转换器）是一个8通道模拟输入的回收型设备。5MHz的A / D转换时钟，最高转换率的1MSPS转换到10-bit/12-bit二进制数字编码的模拟输入信号。A / D转换片上采样和保持功能。支持省电模式。

②特性：

③配置：如果简单的驱动ad，只配置ADCCON寄存器即可，如要实现触摸屏的工能则要其他寄存器

注：在下面代码中我们由此部分的注释

三、linux中的adc驱动程序及注释

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01.#include <linux/kernel.h>
02.#include <linux/module.h>
03.#include <linux/slab.h>
04.#include <linux/input.h>
05.#include <linux/init.h>
06.#include <linux/errno.h>
07.#include <linux/serio.h>
08.#include <linux/delay.h>
09.#include <linux/clk.h>
10.#include <linux/sched.h>
11.#include <linux/cdev.h>
12.#include <linux/miscdevice.h>
13.
14.
15.#include <asm/io.h>
16.#include <asm/irq.h>
17.#include <asm/uaccess.h>
18.
19.#include <mach/map.h>
20.#include <mach/regs-clock.h>
21.#include <mach/regs-gpio.h>
22.#include <plat/regs-adc.h>
23.static void __iomem * base_addr;
24.static struct clk *adc_clock;
25.
26.
27.#define __ADCREG(name) (*(volatile unsigned long *)(base_addr + name))
28.#define ADCCON __ADCREG(S3C_ADCCON) // ADC control
29.#define ADCTSC __ADCREG(S3C_ADCTSC) // ADC touch screen control
30.#define ADCDLY __ADCREG(S3C_ADCDLY) // ADC start or Interval Delay
31.#define ADCDAT0 __ADCREG(S3C_ADCDAT0) // ADC conversion data 0
32.#define ADCDAT1 __ADCREG(S3C_ADCDAT1) // ADC conversion data 1
33.#define ADCUPDN __ADCREG(S3C_ADCUPDN) // Stylus Up/Down interrupt status
34.
35.#define PRESCALE_DIS (0 << 14)
36.#define PRESCALE_EN (1 << 14)
37.#define PRSCVL(x) ((x) << 6)
38.#define ADC_INPUT(x) ((x) << 3)
39.#define ADC_START (1 << 0)
40.#define ADC_ENDCVT (1 << 15)
41.
42.#define DEVICE_NAME "adc_dev"
43.static int adc_init()
44.{
45. unsigned int preScaler = 0XFF;
46. ADCCON = (1<<14)|(preScaler<<6)|(0<<3)|(0<<2);
47. ADCCON |= ADC_START;
48. return 0;
49.}
50.static int adc_open(struct inode *inode ,struct file *filp)
51.{
52. adc_init();
53. return 0;
54.}
55.static int adc_release(struct inode *inode,struct file *filp)
56.{
57. return 0;
58.}
59.static ssize_t adc_read(struct file *filp,char __user *buff,size_t size,loff_t *ppos)
60.{
61. ADCCON |= ADC_START;
62. while(ADCCON & 0x01);//check if Enable_start is low
63. while(!(ADCCON &0x8000));/*检查转换是否结束*/
64. return (ADCDAT0 & 0x3ff);
65.}
66.
67.static struct file_operations dev_fops =
68.{
69. .owner = THIS_MODULE,
70. .open = adc_open,
71. .release = adc_release,
72. .read = adc_read,
73.};
74.
75.static struct miscdevice misc =
76.{
77. .minor = MISC_DYNAMIC_MINOR,
78. .name = DEVICE_NAME,
79. .fops = &dev_fops,
80.};
81.
82.static int __init dev_init()
83.{
84. int ret;
85.
86.
87. base_addr =ioremap(SAMSUNG_PA_ADC,0X20);//地址映射
88. if(base_addr == NULL)
89. {
90. printk(KERN_ERR"failed to remap\n");
91. return -ENOMEM;
92. }
93.
94. adc_clock = clk_get(NULL,"adc");//激活adc时钟模块
95. if(!adc_clock)
96. {
97. printk(KERN_ERR"failed to get adc clock\n");
98. return -ENOENT;
99. }
100. clk_enable(adc_clock);
101.
102.
103. ret = misc_register(&misc);//混杂设备注册
104. printk("dev_init return ret:%d\n",ret);
105. return ret;
106.}
107.static void __exit dev_exit()
108.{
109. iounmap(base_addr);//取消映射
110.
111. if(adc_clock)//disable adc clock取消adc时钟
112. {
113. clk_disable(adc_clock);
114. clk_put(adc_clock);
115. adc_clock =NULL;
116. }
117. misc_deregister(&misc);//注销混杂设备
118.
119.}
120.module_init(dev_init);
121.module_exit(dev_exit);
122.
123.MODULE_LICENSE("GPL");
124.MODULE_AUTHOR("MUGE0913");
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/serio.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/sched.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
#include <mach/map.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>
#include <plat/regs-adc.h>
static void __iomem * base_addr;
static struct clk *adc_clock;
#define __ADCREG(name) (*(volatile unsigned long *)(base_addr + name))
#define ADCCON __ADCREG(S3C_ADCCON) // ADC control
#define ADCTSC __ADCREG(S3C_ADCTSC) // ADC touch screen control
#define ADCDLY __ADCREG(S3C_ADCDLY) // ADC start or Interval Delay
#define ADCDAT0 __ADCREG(S3C_ADCDAT0) // ADC conversion data 0
#define ADCDAT1 __ADCREG(S3C_ADCDAT1) // ADC conversion data 1
#define ADCUPDN __ADCREG(S3C_ADCUPDN) // 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 DEVICE_NAME "adc_dev"
static int adc_init()
{
unsigned int preScaler = 0XFF;
ADCCON = (1<<14)|(preScaler<<6)|(0<<3)|(0<<2);
ADCCON |= ADC_START;
return 0;
}
static int adc_open(struct inode *inode ,struct file *filp)
{
adc_init();
return 0;
}
static int adc_release(struct inode *inode,struct file *filp)
{
return 0;
}
static ssize_t adc_read(struct file *filp,char __user *buff,size_t size,loff_t *ppos)
{
ADCCON |= ADC_START;
while(ADCCON & 0x01);//check if Enable_start is low
while(!(ADCCON &0x8000));/*检查转换是否结束*/
return (ADCDAT0 & 0x3ff);
}
static struct file_operations dev_fops =
{
.owner = THIS_MODULE,
.open = adc_open,
.release = adc_release,
.read = adc_read,
};
static struct miscdevice misc =
{
.minor = MISC_DYNAMIC_MINOR,
.name = DEVICE_NAME,
.fops = &dev_fops,
};
static int __init dev_init()
{
int ret;
base_addr =ioremap(SAMSUNG_PA_ADC,0X20);//地址映射
if(base_addr == NULL)
{
printk(KERN_ERR"failed to remap\n");
return -ENOMEM;
}
adc_clock = clk_get(NULL,"adc");//激活adc时钟模块
if(!adc_clock)
{
printk(KERN_ERR"failed to get adc clock\n");
return -ENOENT;
}
clk_enable(adc_clock);
ret = misc_register(&misc);//混杂设备注册
printk("dev_init return ret:%d\n",ret);
return ret;
}
static void __exit dev_exit()
{
iounmap(base_addr);//取消映射
if(adc_clock)//disable adc clock取消adc时钟
{
clk_disable(adc_clock);
clk_put(adc_clock);
adc_clock =NULL;
}
misc_deregister(&misc);//注销混杂设备
}
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("MUGE0913");