Read temp with DS18S20 temperature sensor

hugo said:

Hi,

Here's an example :

/*
* Project name:
Onewire_Test (Interfacing the DS18x20 temperature sensor - all versions)
* Copyright:
(c) MikroElektronika, 2005-2008.
* Description:
After reset, PIC reads temperature from the sensor and prints it on the Lcd.
The display format of the temperature is 'xxx.xxxx°C'. To obtain correct
results, the 18x20's temperature resolution has to be adjusted (constant
TEMP_RESOLUTION)
* Test configuration:
MCU: PIC16F877A
Dev.Board: EasyPIC4
Oscillator: HS, 08.0000 MHz
Ext. Modules: DS18x20 connected to RE2 pin, LCD_2x16
SW: mikroC v8.0.0.0
* NOTES:
- Pull up and turning off diode on pin used for one wire bus may be required (in this example PORTE)
*/


// Set TEMP_RESOLUTION to the corresponding resolution of used DS18x20 sensor:
// 18S20: 9 (default setting; can be 9,10,11,or 12)
// 18B20: 12
const unsigned short TEMP_RESOLUTION = 9;

char *text = "000.0000";
unsigned temp;

void Display_Temperature(unsigned int temp2write)
{
const unsigned short RES_SHIFT = TEMP_RESOLUTION - 8;
char temp_whole;
unsigned int temp_fraction;

// check if temperature is negative
if (temp2write & 0x8000)
{
text[0] = '-';
temp2write = ~temp2write + 1;
}

// extract temp_whole
temp_whole = temp2write >> RES_SHIFT ;

// convert temp_whole to characters
if (temp_whole/100)
text[0] = temp_whole/100 + 48;

text[1] = (temp_whole/10)%10 + 48; // extract tens digit
text[2] = temp_whole%10 + 48; // extract ones digit

// extract temp_fraction and convert it to unsigned int
temp_fraction = temp2write << (4-RES_SHIFT);
temp_fraction &= 0x000F;
temp_fraction *= 625;

// convert temp_fraction to characters
text[4] = temp_fraction/1000 + 48; // extract thousands digit
text[5] = (temp_fraction/100)%10 + 48; // extract hundreds digit
text[6] = (temp_fraction/10)%10 + 48; // extract tens digit
text[7] = temp_fraction%10 + 48; // extract ones digit

// print temperature on LCD
Lcd_Out(2, 5, text);
}//~

void main()
{
ADCON1 = 7; // Configure AN pins as digital I/O
Lcd_Init(&PORTD); // Lcd_Init_EP4, see Autocomplete
Lcd_Cmd(LCD_CURSOR_OFF);
Lcd_Out(1, 1, " Temperature: ");
// Print degree character, 'C' for Centigrades
Lcd_Chr(2,13,223);
Lcd_Chr(2,14,'C');

//--- main loop
while (1)
{
//--- perform temperature reading
Ow_Reset(&PORTE,2); // Onewire reset signal
Ow_Write(&PORTE,2,0xCC); // Issue command SKIP_ROM
Ow_Write(&PORTE,2,0x44); // Issue command CONVERT_T
Delay_ms(750);

Ow_Reset(&PORTE,2);
Ow_Write(&PORTE,2,0xCC); // Issue command SKIP_ROM
Ow_Write(&PORTE,2,0xBE); // Issue command READ_SCRATCHPAD

temp = Ow_Read(&PORTE,2);
temp = (Ow_Read(&PORTE,2) << 8) + temp;

//--- Format and display result on Lcd
Display_Temperature(temp);

}
}

Click to expand...

garg29 said:

if you want adc type use LM35 which is also cheaper tan DS1820

Click to expand...

min2max said:

I'm aware of the fact that I'm quite 'late' for this thread but still hope to get any response.

I have been stuck by some 18B20 problems these days and have interest in your implementation.

Could you be so kind to post the Ow_xxxx() routines being invoked by the code above?

Click to expand...

The OneWire library provides routines for communication via the Dallas OneWire
protocol, for example with DS18x20 digital thermometer. OneWire is a Master/Slave
protocol, and all communication cabling required is a single wire. OneWire enabled
devices should have open collector drivers (with single pull-up resistor) on the
shared data line.
...
...
Library Routines
- Ow_Reset
- Ow_Read
- Ow_Write

Click to expand...