1: //LCD Display Module Interfacing Example in Hi-Tech PICCLITE C
2: //Number of PIC pins used: 6 (RB5 - RB0)
3: //This example works for any LCD Module made by Optrex, Hitachi, etc.
4: //Two 4-bit nybbles are sent one after the other from the PIC16F877 to the LCD interface,
5: //as explained in Microchip Application Note AN587 (DS00587B - page 3-205)
6: //Chip Type: PIC16F877
7: //Clock Frequency: 13.5 MHz
8: //Written by KEH on 11/01/2003
9: //LCD Display Type: 20 char X 2 line
10: //***********************************************************************
11: //LCD Display Module connections to the PIC
12: // LCD Pin LCD Pin # PIC Sig PIC Pin #
13: // 1 GND --- ---
14: // 2 Vcc --- ---
15: // 3 Vee (Gnded for full contrast)
16: // 4 RS RB5 P38
17: // 5 R/W* (Gnded, since we will only write to LCD module)
18: // 6 E RB4 P37
19: // 7-10 DB0-DB3 (Not used) ---
20: // 11 DB4 RB0 P33
21: // 12 DB5 RB1 P34
22: // 13 DB6 RB2 P35
23: // 14 DB7 RB3 P36
24: //***********************************************************************
25: #include <pic.h>
26: #define RS RB5
27: #define RSCMD 0
28: #define RSDTA 1
29: #define E RB4
30:
31: void initialize_lcd(void);
32: void delayms(unsigned char);
33: void sendnyb(unsigned char);
34: void sendbyte(unsigned char);
35:
36: void main(void)
37: {
38: unsigned char j;
39: PORTB = 0;
40: TRISB = 0xC0; // Make RB5-0 all outputs
41: initialize_lcd();
42: RS=RSDTA;
43: for(j=0;j<20;j++)
44: sendbyte(j+0x41);
45: RS=RSCMD;
46: sendbyte(0b10101000); //Set DDRAM address command
47: //Format (1 a a a a a a a )
48: //Set DDRAM address to 0x28 = 40
49: //This is the starting address
50: //of the 2nd row.
51: RS=RSDTA;
52: for(j=0;j<20;j++)
53: sendbyte(j+0x61);
54: for(;;)
55: continue;
56: }
57:
58:
59: void initialize_lcd(void)
60: {
61: //initializes LCD Display
62: delayms(20);
63: RS=RSCMD;
64: E=0;
65: sendnyb(0x3); // Function Set Command, Gen'l format: 0 0 1 DL N F * *
66: delayms(0x5); // Note that DL = 1 => 8-bit interface mode (Display must be started in 8-bit mode)
67: // Note that the N F * * (low order 4 bits) are not connected, and may be any value.
68: sendnyb(0x3); // Repeat a second time.
69: delayms(0x1);
70: sendnyb(0x3); // Repeat a 3rd time
71: sendnyb(0x2); // Function Set Command - Now we can set interface to 4-bit (nybble) mode
72:
73: // Now that we are in nybble mode, we can send all 8 bits of each command via
74: // two back-to-back calls to sendnyb( ).
75: sendbyte(0x28); // Function Set Command Format: 0 0 1 DL N F * *
76: // We just sent: 0 0 1 0 1 0 0 0
77: // DL=0 => 4-bit mode,
78: // N=1 => 1/8 duty cycle
79: // F=0 => 5 X 7 dot font
80: sendbyte(0x08); // Display OFF command
81: sendbyte(0x01); // Clear Display command
82: sendbyte(0x06); // Entry mode set command format: 0 0 0 0 0 1 I/D S
83: // I/D = 1 => Increment display addr ptr.
84: // S = 0 => Do not shift (scroll) display
85: sendbyte(0x0C); // Display ON command
86: }
87:
88:
89: void delayms(unsigned char nrms)
90: {
91: // Uses Timer #2 to delay the nr of ms specified assuming clock freq = 13.5 MHz
92: unsigned char i;
93: T2CON=0b0000111; //Timer 2 tick time = (4/13.5 Mhz)*16 = 210.93
94: for (i = 0; i < nrms; i++)
95: {
96: TMR2=256-211; //Schedule TMR2IF flag to be set in 1 ms
97: TMR2IF = 0; //Clear TMR2IF timeout flag
98: while(TMR2IF == 0)
99: continue; //Wait here for 1 ms, until TMR2IF flag is set
100: }
101: }
102:
103: void sendnyb(unsigned char sendval)
104: {
105: unsigned char portbval;
106: portbval = PORTB;
107: PORTB = (portbval & 0xF0) + (sendval & 0x0F);
108: //Send out most sig 4 bits of sendval on RB3:0
109: delayms(1);
110: E=1;
111: delayms(1);
112: E=0;
113: delayms(1);
114: }
115:
116: void sendbyte(unsigned char sendval)
117: {
118: sendnyb(sendval >> 4);
119: sendnyb(sendval & 0x0f);
120: }
121:
122: