【Blue Bridge Cup MCU】DS18B20

DS18B20 and the microcontroller use a single bus connection. The file used in the competition is the provided "onewire.c"

Programming steps:

(1) Initialization

(2) Send ROM operation commands, including: Read ROM [33H], Match ROM [55H], Skip ROM [CCH], Search ROM [F0H], Alarm search [ECH]

(3) Send memory operation commands, including: Write Scratchpad (write temporary storage memory) [4EH], Read Scratchpad (read temporary storage memory) [BEH], Copy Scratchpad (copy temporary storage memory) [48H], Convert Temperature (temperature conversion) [44H], Recall EPROM (recall) [B8H], Read Power supply (read power supply) [B4H]

(4) Memory or appropriate delay

PS: When using IAP15, make the following changes to void Delay_OneWire(unsigned int t) in onewire.c:

// Single bus delay function

void Delay_OneWire(unsigned int t)

{

unsigned char i;

while(t--){

for(i=0;i<12;i++);

}

}

Multiply the previous delay time by 12, because the machine cycle of the IAP15 used is the oscillation cycle, and it cannot be read if it is not modified.

Attachment: Code for measuring temperature

uchar low,high;

int gettemper()

{

int t;

Init_DS18B20(); //1. Initialization timing

Write_DS18B20(OW_SKIP_ROM); //2. ROM operation command

    Write_DS18B20(DS18B20_CONVERT); //3. Memory operation command

Delay_OneWire(200);

//end

    Init_DS18B20(); //1. Initialization timing

Write_DS18B20(OW_SKIP_ROM); //2. ROM operation command

    Write_DS18B20(DS18B20_READ); //3. Memory operation command

EA = 0;

low = Read_DS18B20();

high = Read_DS18B20();

    EA = 1;

t = high<<8;

t = t|low;

return t;

// return 0xf13c; //test

}

Does this function return the exact data in the DS18B20 temperature register? If you want to choose to return an integer value or a floating point value, data processing is required.

The delay 2 value (200) cannot be changed.

Appendix: Data processing functions

float get_f_temp()

{

int t;

float temp;

t = gettemper();

if((t&0xf000)>>12 == 0x000f) //negative number

temp = ((~t)+1)*0.0625*(-1.0);

else

temp = t*0.0625;

return temp;

}

Note: When the temperature read is negative, the highest bit returned by gettemper() is 1. In this case, you need to invert the returned value, add 1, and finally multiply it by the 12-bit precision of 0.0625.