18.[stm32] read the ROM of DS18B20 temperature sensor and realize multi-point temperature measurement

Author's brief introduction ： Hello, everyone , My name is DW, Share some of my new knowledge every day , Look forward to making progress with you
   
 
  Series column ：STM32
   
 

  Small experimental target ： Read 3 individual DS18B20 Of ROM And realize multi-point temperature measurement
  If there is anything that is not well written, you are welcome to correct

  Development board ： The punctual atoms STM32F103Mini edition
Creation time ：2022 year 6 month 6 Japan

obtain DS18B20ROM surface  

Written before DS18B20 On the basis of the article , Modify slightly , You can measure each DS18B20 Of 64 position ROM Serial number .

16.[STM32] Start with the principle and let you know DS18B20 Temperature sensor - Four digit digital tube displays the temperature

         One byte is 8 position , We need to read 8 byte ,8 Byte is 64 Bit data , We put 8 Bytes of data are stored in an array , Then print it out through serial port . On the basis of the previous article , Add a read DS18B20ROM Function of .

// Read ROM
void DS18B20_Read_Rom(void){

	u8 rom[8];
	DS18B20_Start_Signal();// Start signal 
	DS18B20_Write_Byte(0x33);// read ROM
	
	for(u8 i=0;i<8;i++){
	
		rom[i] = DS18B20_Read_Byte();// Read a byte 
		printf("%#.2x,",rom[i]);//%#x: Print hexadecimal results preceded by 0X
	}
	printf("\r\n");
}

We use this function , You can read 8 Bytes of data , And print it out through the serial port , This experiment needs to use 3 individual DS18B20, Cannot read all at once 3 individual DS18B20 Of 64 position ROM Serial number , You need to read one by one , Read three times , get 64 position ROM After the serial number, they can be connected to a bus , Then read the temperature at the same time . 

Here is what we got 3 individual DS18B20 Corresponding three groups ROM surface .

  Single bus multipoint temperature measurement

         obtain 3 Group 64 position ROM after , We created 3 An array , Store the read ROM, Only through 64 position ROM We can search the corresponding DS18B20, After through ROM matching , We can match the corresponding on the bus DS18B20, And then realize the conversion of temperature .

u8 rom1[]={0x28,0xd3,0xf6,0x48,0xf6,0xdd,0x3c,0xd5,}; //64 ROM
u8 rom2[]={0x28,0xa3,0xf9,0x96,0xf0,0x01,0x3c,0xf2,};
u8 rom3[]={0x28,0x18,0xa8,0x96,0xf0,0x01,0x3c,0x55,};

matching ROM function  

         Because you need to call the array directly , In order to obtain more accurate data , So we need to set a pointer type variable rom,8 Bytes of ROM Need to write 8 Time , Write one byte at a time .

        You need to send a start signal before writing each byte , Then send the match ROM Instructions 0X55, Finally, write a byte . 

// matching ROM
void DS18B20_Match_Rom(u8 *rom){
	
	DS18B20_Start_Signal();// Start signal 
	DS18B20_Write_Byte(0x55); // matching ROM
	
	for(u8 i=0;i<8;i++){
		
		DS18B20_Write_Byte(*rom++);// Write Bytes 
	}
}

  stay DS18B20 Based on the temperature conversion function , Modify slightly , Add the match just written ROM function , The modified function is as follows .

void DS18B20_Read_Temperature(u8 *rom,u16 *data){
	
	u8 LSB = 0,MSB = 0; 
	u16 Temp = 0;
	// Temperature conversion 
	DS18B20_Match_Rom(rom);// matching ROM
	DS18B20_Write_Byte(0X44);// Temperature change 
	delay_ms(750);
	//12 Bit accuracy  750ms   The nixie tube itself has a time delay , So this delay can be removed 
	DS18B20_Match_Rom(rom);
	DS18B20_Write_Byte(0XBE);// Read temporary storage 
	
	LSB =  DS18B20_Read_Byte();
	MSB =  DS18B20_Read_Byte();
	
	Temp = (MSB<<8) | LSB;// Merge data into 16 position 
	
	if((Temp&0XF800) == 0XF800){ // Negative temperature ;s=1	 Positive temperature ： s=0
	
		*data =(((~Temp+0X01)* -0.0625)+0.5)*10.0;
	}
	else{
		
		*data =((Temp*0.0625)+0.5)*10.0;
	}
}

         Last , stay main Function to call the temperature conversion function and LCD1602 Just display the function . 

#include "delay.h"
#include "lcd1602.h"
#include "DS18b20.h"
#include "usart.h"

u8 rom1[]={0x28,0xd3,0xf6,0x48,0xf6,0xdd,0x3c,0xd5,}; //64 ROM
u8 rom2[]={0x28,0xa3,0xf9,0x96,0xf0,0x01,0x3c,0xf2,};
u8 rom3[]={0x28,0x18,0xa8,0x96,0xf0,0x01,0x3c,0x55,};


int main(){
	
		u16 Temp = 0;
	    delay_init();
		LCD1602_UserConfig();
		LCD1602_Init();
		DS18B20_UserConfig();
		uart_init(115200);
	
	
	while(1){
		
				DS18B20_Read_Rom();// measurement ROM
				delay_ms(1000);
		
		DS18B20_Read_Temperature(rom1,&Temp);
		LCD1602_Number_Display(0XC0,Temp);
		
		DS18B20_Read_Temperature(rom2,&Temp);
		LCD1602_Number_Display(0XC6,Temp);
		
		DS18B20_Read_Temperature(rom3,&Temp);
		LCD1602_Number_Display(0XCC,Temp);
	}
}

         Okay , Let's take a look at the experimental renderings ！ stay LCD1602 Displayed on the 3 A place DS18B20 Measured temperature , Realize multiple DS18B20 Operation connected to a bus .

  Tips ：

        This article selects two pieces 74HC595 drive LCD1602 liquid crystal , If you don't have this chip, you can see the previous fourth article , hold LCD1602 Part of the function can be replaced .

        3 individual DS18B20 It is connected through a bus , Data pin PB0 All connected to DS18B20 On the data bus .

This chapter ends , I'll see you in the next chapter

Reference material ：

1.STM32 Firmware library manual

2. The punctual atoms STM32 Incomplete manual _ Library function version

3. Reference video

4.4.STM32F103-LCD1602 Show characters

5.17.[STM32] Use only three wires to drive you LCD1602 liquid crystal

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