ds18b20/ds18b20.c

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/delay.h>

#include <linux/gpio.h>
#include <linux/of_gpio.h>

unsigned int gpio_num = 0;

#define DQ_IN gpio_direction_input(gpio_num)
//#define DQ_OUT gpio_direction_output(gpio_num, gpio_get_value(gpio_num))
#define DQ_OUT gpio_direction_output(gpio_num, 1)
#define DQ_H gpio_set_value(gpio_num, 1)
#define DQ_L gpio_set_value(gpio_num, 0)
#define DQ_V gpio_get_value(gpio_num)

spinlock_t lock;

//********************************
//功能:ds18b20复位
//********************************
int init_DS18B20(void)
{
	unsigned int result;
	DQ_OUT;
	DQ_L;
	udelay(480);
	DQ_H;
	DQ_IN;
	udelay(65);
	result = DQ_V;
	udelay(240);
    printk("ds18b20 init result %d,%d", result, DQ_V);
	udelay(180);
    return result;
}

//*************************************
//功能:从ds18b20读一个字节的数据
//*************************************
unsigned char read_char(void)
{
    unsigned int i = 0;
    unsigned char dat = 0;

    spin_lock(&lock);
	DQ_OUT;
    for(i=0; i<8; i++) {
		DQ_L;
		udelay(2);
		dat >>= 1;
        DQ_IN;
		udelay(12);
        if (DQ_V)
            dat |= 0x80;
        udelay(50);
		DQ_OUT;
		udelay(2);
    }
    spin_unlock(&lock);
    return dat;
}

//*************************************
//功能:向ds18b20写一个字节的数据
//*************************************
void write_char(unsigned char dat)
{
    unsigned int i = 0;

    spin_lock(&lock);
    DQ_OUT;
    for(i=0; i<8; i++) 
	{
        DQ_L;
        udelay(2);
		if (dat & 0x01)
			DQ_H;
		else
			DQ_L;
        udelay(60);
		DQ_H;
        udelay(2);
		dat >>= 1;
    }
    spin_unlock(&lock);
}

int initDs18b20(unsigned int gpioNum)
{
    spin_lock_init(&lock);
    gpio_num = gpioNum;
    if (init_DS18B20())
    {
        return 1;
    }
    return 0;
}

/*读取数据*/
void readDs18b20Data(unsigned char *value)
{
    if (sizeof(&value) > 1){
        value[0] = 0xff;
        value[1] = 0xff;
    }
    else
    {
        return;
    }
    if (init_DS18B20())
    {
        return;
    }
    write_char(0xCC);
    write_char(0x44);

    mdelay(750);

    if (init_DS18B20())
    {
        return;
    }
    write_char(0xCC);
    write_char(0xBE);

    value[0] = read_char();
    value[1] = read_char();
}

void freeDs18b20(void)
{
    gpio_free(gpio_num);
}