static ssize_t mars_ds18b20_read(struct file *filp, char __user *buf,
size_t size, loff_t *ppos)
{
int flag;
unsigned char msByte = 0, lsByte = 0;
unsigned int temp;
flag = ds18b20_reset();
if (flag & 0x01) {
printk(KERN_WARNING "ds18b20 init failed\n");
return -1;
}
ds18b20_write_byte(0xcc);
ds18b20_write_byte(0x44);
flag = ds18b20_reset();
if (flag & 0x01)
return -1;
ds18b20_write_byte(0xcc);
ds18b20_write_byte(0xbe);
lsByte = ds18b20_read_byte(); // LSB of the temperature
msByte = ds18b20_read_byte(); // MSB of the temperature
temp = msByte;
temp <<= 8;
temp |= lsByte;
if (copy_to_user(buf, &temp, sizeof(temp)))
return -EFAULT;
return sizeof(temp);
}
uint8_t ds18b20_check_crc(){
if(!ds18b20_reset()){
return 0;
}
ds18b20_write_byte(DS18B20_SKIP_ROM);
ds18b20_write_byte(DS18B20_READ_SCRATCHPAD);
uint8_t crc=0;
for(int8_t i=0;i<9;i++){
_crc_ibutton_update(crc,ds18b20_read_byte());
}
return !crc;
}
uint8_t ds18b20_set_precision(uint8_t prec){
if(!ds18b20_reset()){
return 0;
}
ds18b20_write_byte(DS18B20_SKIP_ROM);
ds18b20_write_byte(DS18B20_WRITE_SCRATCHPAD);
ds18b20_write_byte(0);
ds18b20_write_byte(0);
ds18b20_write_byte((prec<<5)|0x1f);
//check crc
if(!ds18b20_check_crc()){
return 0;
}
return 1;
}
uint16_t ds18b20_read(void)
{
uint8_t busy = 0;
uint8_t temp1, temp2;
uint16_t temp;
ds18b20_reset();
/* ds18b20_write_byte(0xCC);*/
ds18b20_write_byte(0x44);
/* while(busy==0)
busy = ds18b20_read_byte();
ds18b20_reset();
ds18b20_write_byte(0xCC);*/
ds18b20_write_byte(0xBE);
temp1 = ds18b20_read_byte();
temp2 = ds18b20_read_byte();
temp = ((uint16_t)temp1 << 8) | temp2;
delay_us(200);
gpio_toggle(GPIOB, GPIO9);
return temp;
}
uint8_t ds18b20_read_temp(double* temp, uint8_t prec){
if(!ds18b20_set_precision(prec)){
return 0;
}
if(!ds18b20_reset()){
return 0;
}
ds18b20_write_byte(DS18B20_SKIP_ROM);
ds18b20_write_byte(DS18B20_CONVERT_T);
// provide power
SET_OUTPUT(DS18B20_DDR, DS18B20_DQ);
SET_HIGH (DS18B20_PORT, DS18B20_DQ);
for(int8_t i=0;i<(1<<prec);i++){
_delay_ms(93.75);
}
if(!ds18b20_reset()){
return 0;
}
ds18b20_write_byte(DS18B20_SKIP_ROM);
ds18b20_write_byte(DS18B20_READ_SCRATCHPAD);
uint8_t crc=0;
uint8_t l=ds18b20_read_byte();
_crc_ibutton_update(crc,l);
uint8_t h=ds18b20_read_byte();
_crc_ibutton_update(crc,h);
for(int8_t i=0;i<7;i++){
_crc_ibutton_update(crc,ds18b20_read_byte());
}
if(crc){
return 0;
}
int16_t t=(h<<8)+l;
*temp=t*0.0625;
return 1;
}
