//DS18S20 (Dallas Semiconductor 1-wire Bus Temperature Sensor) Interfacing Example in PICCLITE.
//PIC pins used: LCD Display: RB5 - RB0, Temp Sensor: RD0.
//This example works for any LCD Module made by Optrex, Hitachi, etc.
//This example is based on information in the DS18S20 datasheet
//and Dallas Semiconductor App Note #162 "Interfacing the DS18x20 1-wire temp
//sensor in a microcontroller environment
//Chip Type: PIC16F877
//Clock Frequency: 13.5 MHz
//Written by KEH on 11/01/2003
//LCD Display Type: 20 char X 2 line
//***********************************************************************
//LCD Display Module connections to the PIC
// LCD Pin LCD Pin # PIC Sig PIC Pin #
// 1 GND --- ---
// 2 Vcc --- ---
// 3 Vee (Gnded for full contrast)
// 4 RS RB5 P38
// 5 R/W* (Gnded, since we will only write to LCD module)
// 6 E RB4 P37
// 7-10 DB0-DB3 (Not used) ---
// 11 DB4 RB0 P33
// 12 DB5 RB1 P34
// 13 DB6 RB2 P35
// 14 DB7 RB3 P36
//***********************************************************************
#include <pic.h>
#define RS RB5
#define RSCMD 0
#define RSDTA 1
#define E RB4
void initialize_lcd(void);
void delayms(unsigned char);
void lcdsendnyb(unsigned char);
void lcdsendbyte(unsigned char);
unsigned char one_wire_reset(void);
void delay6us(unsigned int);
void write_byte_one_wire(char);
unsigned char read_byte_one_wire(void);
unsigned char write_bit_one_wire(char);
unsigned char read_bit_one_wire(void);
unsigned char presence;
void main(void)
{
unsigned char j;
char scratchdat[10],msbtemp,lsbtemp;
int temp,quot,lschar,middlechar,mschar,fractchar;
PORTB = 0;
TRISB = 0xC0; // Make RB5-0 all outputs
TRISD0 = 1; //RD0 is pulled high through 4.7 kilohm external pullup resistor.
initialize_lcd();
for(;;)
{
one_wire_reset();
write_byte_one_wire(0xcc); //skip ROM
write_byte_one_wire(0x44); //Start Conversion
delay6us(18);
one_wire_reset();
write_byte_one_wire(0xcc); //Skip ROM
write_byte_one_wire(0xBE); //Read Scratch Pad inside Temp Sensor
lsbtemp = read_byte_one_wire();
msbtemp = read_byte_one_wire();
for(j=0;j<7;j++)
scratchdat[j] = read_byte_one_wire();
temp = lsbtemp + (msbtemp<<8);
if (temp & 1 == 1) fractchar = '5'; else fractchar = '0';
temp = temp>>1; //Get the temperature in degrees C instead of half degrees
quot = temp/10;
lschar = (temp - 10*quot) + 0x30;
temp = quot;
quot = temp/10;
middlechar = (temp - 10*quot) + 0x30;
temp = quot;
quot = temp/10;
mschar = (temp - 10*quot) + 0x30;
RS=RSDTA;
lcdsendbyte(mschar);
lcdsendbyte(middlechar);
lcdsendbyte(lschar);
lcdsendbyte('.');
lcdsendbyte(fractchar);
RS=RSCMD;
lcdsendbyte(2); //Position Cursor at "Home Position"
}
}
void initialize_lcd(void)
{
//initializes LCD Display
delayms(20);
RS=RSCMD;
E=0;
lcdsendnyb(0x3); // Function Set Command, Gen'l format: 0 0 1 DL N F * *
delayms(0x5); // Note that DL = 1 => 8-bit interface mode (Display must be started in 8-bit mode)
// Note that the N F * * (low order 4 bits) are not connected, and may be any value.
lcdsendnyb(0x3); // Repeat a second time.
delayms(0x1);
lcdsendnyb(0x3); // Repeat a 3rd time
lcdsendnyb(0x2); // Function Set Command - Now we can set interface to 4-bit (nybble) mode
// Now that we are in nybble mode, we can send all 8 bits of each command via
// two back-to-back calls to lcdsendnyb( ).
lcdsendbyte(0x28); // Function Set Command Format: 0 0 1 DL N F * *
// We just sent: 0 0 1 0 1 0 0 0
// DL=0 => 4-bit mode,
// N=1 => 1/8 duty cycle
// F=0 => 5 X 7 dot font
lcdsendbyte(0x08); // Display OFF command
lcdsendbyte(0x01); // Clear Display command
lcdsendbyte(0x06); // Entry mode set command format: 0 0 0 0 0 1 I/D S
// I/D = 1 => Increment display addr ptr.
// S = 0 => Do not shift (scroll) display
lcdsendbyte(0x0C); // Display ON command
}
void delayms(unsigned char nrms)
{
// Uses Timer #2 to delay the nr of ms specified assuming clock freq = 13.5 MHz
unsigned char i;
T2CON=0b0000111; //Timer 2 tick time = (4/13.5 Mhz)*16 = 0.474E-5 s
//Nr Ticks in 1 ms = 1E-3 / 0.474E-5 = 210.94 ticks.
for (i = 0; i < nrms; i++)
{
TMR2=256-211; //Schedule TMR2IF flag to be set in 1 ms
TMR2IF = 0; //Clear TMR2IF timeout flag
while(TMR2IF == 0)
continue; //Wait here for 1 ms, until TMR2IF flag is set
}
}
void delay6us(unsigned int nr6us)
{ unsigned int i;
for (i = 0; i < nr6us; i++)
{
continue;
}
}
void lcdsendnyb(unsigned char sendval)
{
unsigned char portbval;
portbval = PORTB;
PORTB = (portbval & 0xF0) + (sendval & 0x0F);
//Send out most sig 4 bits of sendval on RB3:0
delayms(1);
E=1;
delayms(1);
E=0;
delayms(1);
}
void lcdsendbyte(unsigned char sendval)
{
lcdsendnyb(sendval >> 4);
lcdsendnyb(sendval & 0x0f);
}
unsigned char one_wire_reset(void)
{
RD0 = 0;
TRISD0 = 0; //Pull DQ line low
delay6us(80); //Wait for 480 US
TRISD0 = 1; //Allow DQ to e pulled high
delay6us(12); //Wait for 70 US
presence = RD0; //Read state of DQ (hopefully presence pulse is being sent by temp sens)
delay6us(68); //Wait 410 US for presence pulse to finish
return(presence);
}
unsigned char read_bit_one_wire(void)
{
unsigned char i;
RD0 = 0;
TRISD0 = 0; //Pull DQ low to start timeslot
TRISD0 = 1; //Then let DQ line be pulled high.
delay6us(1); //delay 15 us from start of timeslot
return(RD0); //return value of DQ line (as set by temp sens)
}
unsigned char write_bit_one_wire(char bitval)
{ RD0 = 0;
TRISD = 0; //Pull DQ low to start timeslot
if(bitval == 1) TRISD = 1; //Let DQ go high to write a 1
delay6us(18); //delay 108 us
TRISD0 = 1; //Let DQ line go high to end cycle
}
unsigned char read_byte_one_wire(void)
{
unsigned char i;
unsigned char value = 0;
for(i=0;i<8;i++)
{
if(read_bit_one_wire()) value=value | 1<<i; //Read byte in one bit at a time
delay6us(18); //Wait for rest of timeslot
}
return(value);
}
void write_byte_one_wire(char val)
{
unsigned char i;
unsigned char temp;
for(i=0;i<8;i++) //Write byte, one bit at a time
{
temp = val>>i; //Shift ith bit into LSB position
temp = temp & 1; //Mask out LSB bit value
write_bit_one_wire(temp); //Write it to temp sensor
}
delay6us(18);
}