为什么ds18b20接上stm32单片机之后 就一直在oled显示零度。

[花堪诉落尽之殇]

main
#include "sys.h"
#include "delay.h"
#include "usart.h"
#include "led.h"
#include "ds18b20.h"
#include "oled.h"


double temp;
uint8_t disbuf[16];
int main(void)
{


NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
delay_init(168);
uart_init(115200);

LED_Init();
OLED_Init();

DS18B20_Init();

while(1)
{
temp=DS18B20_Get_Temp();
temp/=10;
if(temp<20)
{
LED0=0;
}
if(temp>40)
{
LED1=0;
}
sprintf((char *)disbuf,"Temp:%.1f C",temp);
OLED_ShowString(0,0,disbuf,24);
OLED_ShowString(100,0," C",24);
OLED_Refresh_Gram();
delay_ms(100)；
}


}




ds18b20.h
#define DS18B20_IO_IN() {GPIOB->MODER&=~(3<<(7*2));GPIOB->MODER|=0<<7*2;}
#define DS18B20_IO_OUT() {GPIOB->MODER&=~(3<<(7*2));GPIOB->MODER|=1<<7*2;}


#define DS18B20_DQ_OUT PBout(7)
#define DS18B20_DQ_IN PBin(7)

u8 DS18B20_Init(void);
short DS18B20_Get_Temp(void);
void DS18B20_Start(void);
void DS18B20_Write_Byte(u8 dat);
u8 DS18B20_Read_Byte(void);
u8 DS18B20_Read_Bit(void);
u8 DS18B20_Check(void);
void DS18B20_Rst(void);
#endif

ds18b20.c
#include "ds18b20.h"
#include "delay.h"

u8 DS18B20_Check(void)
{
u8 retry=0;
DS18B20_IO_IN();//SET PG11 INPUT
while (DS18B20_DQ_IN&&retry<200)
{
retry++;
delay_us(1);
};
if(retry>=200)return 1;
else retry=0;
while (!DS18B20_DQ_IN&&retry<240)
{
retry++;
delay_us(1);
};
if(retry>=240)return 1;
return 0;
}

u8 DS18B20_Read_Bit(void) // read one bit
{
u8 data;
DS18B20_IO_OUT();//SET PG11 OUTPUT
DS18B20_DQ_OUT=0;
delay_us(2);
DS18B20_DQ_OUT=1;
DS18B20_IO_IN();//SET PG11 INPUT
delay_us(12);
if(DS18B20_DQ_IN)data=1;
else data=0;
delay_us(50);
return data;
}

u8 DS18B20_Read_Byte(void) // read one byte
{
u8 i,j,dat;
dat=0;
for (i=1;i<=8;i++)
{
j=DS18B20_Read_Bit();
dat=(j<<7)|(dat>>1);
}
return dat;
}
void DS18B20_Write_Byte(u8 dat)
{
u8 j;
u8 testb;
DS18B20_IO_OUT();//SET PG11 OUTPUT;
for (j=1;j<=8;j++)
{
testb=dat&0x01;
dat=dat>>1;
if (testb)
{
DS18B20_DQ_OUT=0;// Write 1
delay_us(2);
DS18B20_DQ_OUT=1;
delay_us(60);
}
else
{
DS18B20_DQ_OUT=0;// Write 0
delay_us(60);
DS18B20_DQ_OUT=1;
delay_us(2);
}
}
}

void DS18B20_Start(void)// ds1820 start convert
{
DS18B20_Rst();
DS18B20_Check();
DS18B20_Write_Byte(0xcc);// skip rom
DS18B20_Write_Byte(0x44);// convert
}

u8 DS18B20_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);//ʹÄÜGPIOGʱÖÓ

//GPIOG9
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOB, &GPIO_InitStructure);¯

DS18B20_Rst();
return DS18B20_Check();
}

short DS18B20_Get_Temp(void)
{
u8 temp;
u8 TL,TH;
short tem;
DS18B20_Start (); // ds1820 start convert
DS18B20_Rst();
DS18B20_Check();
DS18B20_Write_Byte(0xcc);// skip rom
DS18B20_Write_Byte(0xbe);// convert
TL=DS18B20_Read_Byte(); // LSB
TH=DS18B20_Read_Byte(); // MSB
if(TH>7)
{
TH=~TH;
TL=~TL;
temp=0;
}else temp=1;
tem=TH;
tem<<=8;
tem+=TL;
tem=(double)tem*0.625;
if(temp)return tem;
else return -tem;
}

[lfdcn]

我觉得是数据类型的问题，DS18B20程序看着没问题，觉得转换可能消耗了。

[worldy]

肯定是DS18B20读数错误，读错误的最大可能是各脉冲时长不足