1: //DS18S20 (Dallas Semiconductor 1-wire Bus Temperature Sensor) Interfacing Example in PICCLITE.
2: //PIC pins used: LCD Display: RB5 - RB0, Temp Sensor: RD0.
3: //This example works for any LCD Module made by Optrex, Hitachi, etc.
4: //This example is based on information in the DS18S20 datasheet
5: //and Dallas Semiconductor App Note #162 "Interfacing the DS18x20 1-wire temp
6: //sensor in a microcontroller environment
7: //Chip Type: PIC16F877
8: //Clock Frequency: 13.5 MHz
9: //Written by KEH on 11/01/2003
10: //LCD Display Type: 20 char X 2 line
11: //***********************************************************************
12: //LCD Display Module connections to the PIC
13: // LCD Pin LCD Pin # PIC Sig PIC Pin #
14: // 1 GND --- ---
15: // 2 Vcc --- ---
16: // 3 Vee (Gnded for full contrast)
17: // 4 RS RB5 P38
18: // 5 R/W* (Gnded, since we will only write to LCD module)
19: // 6 E RB4 P37
20: // 7-10 DB0-DB3 (Not used) ---
21: // 11 DB4 RB0 P33
22: // 12 DB5 RB1 P34
23: // 13 DB6 RB2 P35
24: // 14 DB7 RB3 P36
25: //***********************************************************************
26: #include <pic.h>
27: #define RS RB5
28: #define RSCMD 0
29: #define RSDTA 1
30: #define E RB4
31:
32: void initialize_lcd(void);
33: void delayms(unsigned char);
34: void lcdsendnyb(unsigned char);
35: void lcdsendbyte(unsigned char);
36:
37: unsigned char one_wire_reset(void);
38: void delay6us(unsigned int);
39: void write_byte_one_wire(char);
40: unsigned char read_byte_one_wire(void);
41: unsigned char write_bit_one_wire(char);
42: unsigned char read_bit_one_wire(void);
43: unsigned char presence;
44:
45: void main(void)
46: {
47: unsigned char j;
48: char scratchdat[10],msbtemp,lsbtemp;
49: int temp,quot,lschar,middlechar,mschar,fractchar;
50:
51: PORTB = 0;
52: TRISB = 0xC0; // Make RB5-0 all outputs
53: TRISD0 = 1; //RD0 is pulled high through 4.7 kilohm external pullup resistor.
54: initialize_lcd();
55: for(;;)
56: {
57: one_wire_reset();
58: write_byte_one_wire(0xcc); //skip ROM
59: write_byte_one_wire(0x44); //Start Conversion
60: delay6us(18);
61: one_wire_reset();
62: write_byte_one_wire(0xcc); //Skip ROM
63: write_byte_one_wire(0xBE); //Read Scratch Pad inside Temp Sensor
64: lsbtemp = read_byte_one_wire();
65: msbtemp = read_byte_one_wire();
66: for(j=0;j<7;j++)
67: scratchdat[j] = read_byte_one_wire();
68: temp = lsbtemp + (msbtemp<<8);
69: if (temp & 1 == 1) fractchar = '5'; else fractchar = '0';
70: temp = temp>>1; //Get the temperature in degrees C instead of half degrees
71: quot = temp/10;
72: lschar = (temp - 10*quot) + 0x30;
73: temp = quot;
74: quot = temp/10;
75: middlechar = (temp - 10*quot) + 0x30;
76: temp = quot;
77: quot = temp/10;
78: mschar = (temp - 10*quot) + 0x30;
79: RS=RSDTA;
80: lcdsendbyte(mschar);
81: lcdsendbyte(middlechar);
82: lcdsendbyte(lschar);
83: lcdsendbyte('.');
84: lcdsendbyte(fractchar);
85: RS=RSCMD;
86: lcdsendbyte(2); //Position Cursor at "Home Position"
87: }
88: }
89:
90:
91: void initialize_lcd(void)
92: {
93: //initializes LCD Display
94: delayms(20);
95: RS=RSCMD;
96: E=0;
97: lcdsendnyb(0x3); // Function Set Command, Gen'l format: 0 0 1 DL N F * *
98: delayms(0x5); // Note that DL = 1 => 8-bit interface mode (Display must be started in 8-bit mode)
99: // Note that the N F * * (low order 4 bits) are not connected, and may be any value.
100: lcdsendnyb(0x3); // Repeat a second time.
101: delayms(0x1);
102: lcdsendnyb(0x3); // Repeat a 3rd time
103: lcdsendnyb(0x2); // Function Set Command - Now we can set interface to 4-bit (nybble) mode
104:
105: // Now that we are in nybble mode, we can send all 8 bits of each command via
106: // two back-to-back calls to lcdsendnyb( ).
107: lcdsendbyte(0x28); // Function Set Command Format: 0 0 1 DL N F * *
108: // We just sent: 0 0 1 0 1 0 0 0
109: // DL=0 => 4-bit mode,
110: // N=1 => 1/8 duty cycle
111: // F=0 => 5 X 7 dot font
112: lcdsendbyte(0x08); // Display OFF command
113: lcdsendbyte(0x01); // Clear Display command
114: lcdsendbyte(0x06); // Entry mode set command format: 0 0 0 0 0 1 I/D S
115: // I/D = 1 => Increment display addr ptr.
116: // S = 0 => Do not shift (scroll) display
117: lcdsendbyte(0x0C); // Display ON command
118: }
119:
120:
121: void delayms(unsigned char nrms)
122: {
123: // Uses Timer #2 to delay the nr of ms specified assuming clock freq = 13.5 MHz
124: unsigned char i;
125: T2CON=0b0000111; //Timer 2 tick time = (4/13.5 Mhz)*16 = 0.474E-5 s
126: //Nr Ticks in 1 ms = 1E-3 / 0.474E-5 = 210.94 ticks.
127: for (i = 0; i < nrms; i++)
128: {
129: TMR2=256-211; //Schedule TMR2IF flag to be set in 1 ms
130: TMR2IF = 0; //Clear TMR2IF timeout flag
131: while(TMR2IF == 0)
132: continue; //Wait here for 1 ms, until TMR2IF flag is set
133: }
134: }
135:
136:
137: void delay6us(unsigned int nr6us)
138: { unsigned int i;
139: for (i = 0; i < nr6us; i++)
140: {
141: continue;
142: }
143: }
144:
145: void lcdsendnyb(unsigned char sendval)
146: {
147: unsigned char portbval;
148: portbval = PORTB;
149: PORTB = (portbval & 0xF0) + (sendval & 0x0F);
150: //Send out most sig 4 bits of sendval on RB3:0
151: delayms(1);
152: E=1;
153: delayms(1);
154: E=0;
155: delayms(1);
156: }
157:
158: void lcdsendbyte(unsigned char sendval)
159: {
160: lcdsendnyb(sendval >> 4);
161: lcdsendnyb(sendval & 0x0f);
162: }
163:
164: unsigned char one_wire_reset(void)
165: {
166: RD0 = 0;
167: TRISD0 = 0; //Pull DQ line low
168: delay6us(80); //Wait for 480 US
169: TRISD0 = 1; //Allow DQ to e pulled high
170: delay6us(12); //Wait for 70 US
171: presence = RD0; //Read state of DQ (hopefully presence pulse is being sent by temp sens)
172: delay6us(68); //Wait 410 US for presence pulse to finish
173: return(presence);
174: }
175:
176: unsigned char read_bit_one_wire(void)
177: {
178: unsigned char i;
179: RD0 = 0;
180: TRISD0 = 0; //Pull DQ low to start timeslot
181: TRISD0 = 1; //Then let DQ line be pulled high.
182: delay6us(1); //delay 15 us from start of timeslot
183: return(RD0); //return value of DQ line (as set by temp sens)
184: }
185:
186: unsigned char write_bit_one_wire(char bitval)
187: { RD0 = 0;
188: TRISD = 0; //Pull DQ low to start timeslot
189: if(bitval == 1) TRISD = 1; //Let DQ go high to write a 1
190: delay6us(18); //delay 108 us
191: TRISD0 = 1; //Let DQ line go high to end cycle
192: }
193:
194: unsigned char read_byte_one_wire(void)
195: {
196: unsigned char i;
197: unsigned char value = 0;
198:
199: for(i=0;i<8;i++)
200: {
201: if(read_bit_one_wire()) value=value | 1<<i; //Read byte in one bit at a time
202: delay6us(18); //Wait for rest of timeslot
203: }
204: return(value);
205: }
206:
207: void write_byte_one_wire(char val)
208: {
209: unsigned char i;
210: unsigned char temp;
211:
212: for(i=0;i<8;i++) //Write byte, one bit at a time
213: {
214: temp = val>>i; //Shift ith bit into LSB position
215: temp = temp & 1; //Mask out LSB bit value
216: write_bit_one_wire(temp); //Write it to temp sensor
217: }
218: delay6us(18);
219: }