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代码下载地址

https://gitee.com/jeasonb/imx6ull_adc

注意： 以下的所有的代码框架来自韦东山老师的代码。

今天来尝试一下ADC驱动的开发。平台是基于野火的 imx6ullpro 开发板。 内核是4.1.15版本。注意：这只是一个简单的demo,我可能会忽略那些adc时钟倍频之类的东西，毕竟作为一个测试的demo,应该是用不上太高的采样。

1.整体的思路

第一步就是字符设备驱动的框架，这一部分不需要去纠结，直接就是 init/exit/open/read/write/close 这几个函数，按照套路来就行了。

2. 开发流程

2.1 字符设备驱动框架的迁移

这一部分没什么技术含量，就是简单的代码的复制。我们需要去实现以下的函数

static int major = 0;static struct class *adc_class;static struct file_operations adc_drv = {
   	.owner	 = THIS_MODULE,	.open    = adc_drv_open,	.read    = adc_drv_read,	//.write   = adc_drv_write,	.release = adc_drv_close,};static int     adc_drv_open (struct inode *node, struct file *file); // 启动adc,配置必要的参数static ssize_t adc_drv_read (struct file *file, char __user *buf, siz_t size, loff_t *offset);   // 开启adc转换//static ssize_t adc_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset);// 空函数static int     adc_drv_close (struct inode *node, struct file *file); // 关闭adc,释放引脚，时钟等static int __init adc_init(void);   // 初始化函数 ioremapstatic void __exit adc_exit(void);  // 释放函数   iounmapmodule_init(adc_init);module_exit(adc_exit);MODULE_LICENSE("GPL");

由于这一部分确实没啥好说的，一笔带过。

2.2 硬件操作分析

在进行硬件操作之前我们需要先分析开发板给我们提供的学习环境，也就是ADC功能他是接到了哪一个引脚上去了。

野火原理图如下：（git上doc路径下有原理图以及用户手册）

2.2.1.开时钟

imx6ull的时钟是CCM管理的，这一点跟stm32F4的RCC很相似，在我们的驱动中需要做的就是在init的时候把这个时钟寄存器ioremap,然后打开对应的时钟，在exit函数中把这个时钟关闭然后iounmap。接下来找一下 adc1的时钟。

// i.mx6ull CCM_CCGR1  0x020C 406Cvolatile unsigned int *CCM_CCGR1; // adc1 时钟开启bit 位于此

开时钟的这个过程我是在加载驱动的时候就进行的，在驱动加载的时候直接打开adc的时钟

其中的相关的代码片段如下：

volatile unsigned int *CCM_CCGR1 = NULL; // adc1 时钟开启bit 位于此// adc_init()  中  CCM_CCGR1 = ioremap(0x020C406C,sizeof(volatile unsigned int));	//adc_drv_open() 中if(CCM_CCGR1)	*CCM_CCGR1 |= (3<<16);  // 使能ADC时钟//adc_drv_close()if(CCM_CCGR1)   *CCM_CCGR1 &= ~(3<<16); // 关ADC 时钟// adc_exit()  中  iounmap(0x020C406C,1);

2.2.2 配置复用

// io realated  IOmux//  IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03    20E_0068volatile unsigned int *IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03;//  IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03    20E_02F4volatile unsigned int *IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03;//adc_init()IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = ioremap(0x020E0068,sizeof(unsigned int));IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = ioremap(0x020E02F4,sizeof(unsigned int));//adc_drv_open()if(IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03)	*IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = 1<<4;	if(IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03)	*IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = 0;//adc_drv_close()if(IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03)	*IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = 0;	if(IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03)	*IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = 0;

2.2.3 配置ADC

//  i.mx6ull adc1 base 0x0219 8000//  i.mx6ull adc2 base 0x0219 c000struct imx6ull_adc {
       volatile unsigned int adc_hc0; //Control register    volatile unsigned int adc_hs;  //Status register    volatile unsigned int adc_r0;  //Data result registe    volatile unsigned int adc_cfg; //Configuration register    volatile unsigned int adc_gc;  //General control register    volatile unsigned int adc_gs;  //General status register    volatile unsigned int adc_cv;  //Compare value registe    volatile unsigned int adc_ofs; //Offset correction value register    volatile unsigned int adc_cal; //Calibration value register };struct imx6ull_adc *adc1;//adc_init()adc1      = ioremap(0x02198000,sizeof(struct imx6ull_adc));		//adc_drv_open()	if(adc1)	{
   		adc1->adc_cfg = (2<<2); //  默认的情况下也能用，如果对性能有要求才需要修改参数	//	adc_cfg[16]   : OVWREN Data Overwrite Enable = false	//  adc_cfg[15:14]: 00 4 samples averaged   四倍过采样	//  adc_cfg[13]   : Conversion Trigger Select, 0 Software trigger selected	//  adc_cfg[12:11]: Voltage Reference Selection,00 Selects VREFH/VREFL as reference voltage.	//	adc_cfg[10]   ：High Speed Configuration，   0 Normal conversion selected	//	adc_cfg[9:8]  ：ADSTS，00 Sample period (ADC clocks) = 2 if ADLSMP=0b	//	adc_cfg[7]    : Low-Power Configuration,0 ADC hard block not in low power mode.	//	adc_cfg[6:5]  : Clock Divide Select,00 Input clock	//  adc_cfg[4]    : Long Sample Time Configuration,0 Short sample mode.	//	adc_cfg[3:2]  : Conversion Mode Selection,00 8-bit conversion	//  adc_cfg[1:0]  : Input Clock Select,00 IPG clock		adc1->adc_hc0 = 3; // 通道选择为3，并且不使能中断		adc1->adc_gc = 0;//  一些进阶功能，目前应该用不到。	}//adc_drv_read()	adc1->adc_hc0 = 3;// 选择通道	while(adc1->adc_hs == 0) //等待 状态寄存器	{
   		if(cnt++ > 100000) 		{
   			printk("over time!\n");			break;		}	}	if(size > 4) size = 4; // 最多允许读四字节	value = 0xfff & adc1->adc_r0;	err = copy_to_user(buf, &value, size);	//adc_exit()iounmap(adc1);

2.3 测试程序

#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         int main(int argc, char **argv){ int fd; unsigned int buf[2]; int bytes = 0; fd = open("/dev/adc3", O_RDWR); while(1) { bytes = read(fd, buf, 4); if(bytes) printf("%d\n",buf[0]); else break; usleep(100000); } printf("done !\n"); close(fd); return 0;}
        
       
      
     
    
   

完整版 驱动代码 框架来自韦东山老师的代码框架

#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
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           #include 
           
            #include 
            
             #include 
             
              #include 
              
               #include 
               
                #include 
                
                 #include 
                 
                  #include 
                  
                   /* 1. 确定主设备号 */static int major = 0;static struct class *adc_class = NULL;// i.mx6ull CCM_CCGR1 0x020C 406Cvolatile unsigned int *CCM_CCGR1 = NULL; // adc1 时钟开启bit 位于此// i.mx6ull adc1 base 0x0219 8000// i.mx6ull adc2 base 0x0219 c000struct imx6ull_adc { volatile unsigned int adc_hc0; //Control register volatile unsigned int notused1;// 04 volatile unsigned int adc_hs; //Status register volatile unsigned int adc_r0; //Data result registe volatile unsigned int notused2;// 10 volatile unsigned int adc_cfg; //Configuration register volatile unsigned int adc_gc; //General control register volatile unsigned int adc_gs; //General status register volatile unsigned int adc_cv; //Compare value registe volatile unsigned int adc_ofs; //Offset correction value register volatile unsigned int adc_cal; //Calibration value register };struct imx6ull_adc *adc1 = NULL;// io realated IOmux// IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 20E_0068volatile unsigned int *IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = NULL;// IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 20E_02F4volatile unsigned int *IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = NULL;#define MIN(a, b) (a < b ? a : b)/* 3. 实现对应的open/read/write等函数，填入file_operations结构体 */static ssize_t adc_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset){ int err; //unsigned long copy_to_user(void *to, const void *from, unsigned long n) //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unsigned int value = 0; int cnt=0; value = 0xfff & adc1->adc_r0; adc1->adc_hc0 = 3; while(adc1->adc_hs == 0) //等待 状态寄存器 { if(cnt++ > 100000) { printk("over time!\n"); break; } } if(size > 4) size = 4; // 最多允许读四字节 value = 0xfff & adc1->adc_r0; err = copy_to_user(buf, &value, size); return size;}/* write(fd, &val, 1); *///static ssize_t adc_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset)//{ // return 0;//}static int adc_drv_open (struct inode *node, struct file *file){ //int minor = iminor(node); //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);/* 根据次设备号初始化LED */// p_led_opr->init(minor); //printk("here should init adc!\n"); if(CCM_CCGR1) *CCM_CCGR1 |= (3<<16); if(IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03) *IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = 1<<4; if(IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03) *IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = 0; if(adc1) { adc1->adc_cfg = (2<<2); // 默认的情况下也能用，如果对性能有要求才需要修改参数 // adc_cfg[16] : OVWREN Data Overwrite Enable = false // adc_cfg[15:14]: 00 4 samples averaged 四倍过采样 // adc_cfg[13] : Conversion Trigger Select, 0 Software trigger selected // adc_cfg[12:11]: Voltage Reference Selection,00 Selects VREFH/VREFL as reference voltage. // adc_cfg[10] ：High Speed Configuration， 0 Normal conversion selected // adc_cfg[9:8] ：ADSTS，00 Sample period (ADC clocks) = 2 if ADLSMP=0b // adc_cfg[7] : Low-Power Configuration,0 ADC hard block not in low power mode. // adc_cfg[6:5] : Clock Divide Select,00 Input clock // adc_cfg[4] : Long Sample Time Configuration,0 Short sample mode. // adc_cfg[3:2] : Conversion Mode Selection,00 8-bit conversion // adc_cfg[1:0] : Input Clock Select,00 IPG clock adc1->adc_hc0 = 3; // 通道选择为3，并且不使能中断 adc1->adc_gc = 0;// 一些进阶功能，目前应该用不到。 } return 0;}static int adc_drv_close (struct inode *node, struct file *file){ //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); if(CCM_CCGR1) *CCM_CCGR1 &= ~(3<<16); // 关ADC 时钟 if(IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03) *IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = 0; if(IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03) *IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = 0; //printk("here should uninit adc!\n"); return 0;}/* 2. 定义自己的file_operations结构体 */static struct file_operations adc_drv = { .owner = THIS_MODULE, .open = adc_drv_open, .read = adc_drv_read, //.write = adc_drv_write, .release = adc_drv_close,};/* 4. 把file_operations结构体告诉内核：注册驱动程序 *//* 5. 谁来注册驱动程序啊？得有一个入口函数：安装驱动程序时，就会去调用这个入口函数 */static int __init adc_init(void){ //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); major = register_chrdev(0, "adc", &adc_drv); /* /dev/led */ adc_class = class_create(THIS_MODULE, "adc_class"); device_create(adc_class, NULL, MKDEV(major, 3), NULL, "adc%d", 3); CCM_CCGR1 = ioremap(0x020C406C,sizeof(unsigned int)); adc1 = ioremap(0x02198000,sizeof(struct imx6ull_adc)); IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = ioremap(0x020E0068,sizeof(unsigned int)); IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03 = ioremap(0x020E02F4,sizeof(unsigned int)); return 0;}/* 6. 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */static void __exit adc_exit(void){ //int i; printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(adc_class, MKDEV(major, 3)); class_destroy(adc_class); unregister_chrdev(major, "adc"); iounmap(CCM_CCGR1); iounmap(IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03); iounmap(IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO03); iounmap(adc1);}/* 7. 其他完善：提供设备信息，自动创建设备节点 */module_init(adc_init);module_exit(adc_exit);MODULE_LICENSE("GPL");
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    
   

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