Flexible LCD driver

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

This post has the code for the 16x2 LCD driver.

The 20x4 LCD driver is at the following link:
http://www.ccsinfo.com/forum/viewtopic.php?t=28268
The 16x1 LCD driver is at the following link:
http://www.ccsinfo.com/forum/viewtopic.php?t=30964

------------
Flexible driver for a 16x2 LCD:
This is an adaptation of the CCS LCD driver. This isn't intended to
replace the CCS driver or Mark's driver. It's just another option
that I decided to put out there.

Advantages:

1. This driver allows you to simply specify the LCD pins at the top of
the file. This would be useful if your board doesn't fit the CCS driver,
and you don't want to spend the time to figure out how to modify the
CCS driver.

2. You can put the LCD pins on several different ports. Also, the data
bus pins don't have to be in numerical order or on the same port.

Disadvantages or Limitations:

1. This driver requires CCS "standard i/o" mode (The default mode
of the compiler). If you want to use fast i/o mode, then use the CCS
driver or Mark's driver:
http://www.ccsinfo.com/forum/viewtopic.php?t=20182

2. This driver uses about 50% more ROM than the CCS driver.
That's because it does individual pin i/o rather than byte-wide i/o,
and because it uses standard i/o mode.

Why use it ?

1. If you decide to add LCD support to a board and the only available
pins are spread out over several ports, then this driver can help you.

2. If you're a newbie and your board isn't configured to use the
CCS driver, and you don't know how to modify it or Mark's driver,
then this driver can get you up running quickly.

Choosing i/o pins:
1. You must make sure that you choose i/o pins for the data bus
signals and output pins for the 3 control signals. On some PICs,
certain pins are input-only. Make sure that if you use Pin A4,
that you put a pull-up resistor on it. Also, if you're using an
analog or a comparator pin, make sure that you use the proper
CCS function to configure it as a normal i/o pin.

jruibarroso · Joined: 07 Jan 2006 Posts: 64 Location: Braga

hi, I'm actually using this driver you posted and works really fine.
I wonder if you can add the necessary code to work on 4 lines LCDs, thank you

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I don't have a 4-line LCD to test. But I can modify the driver so that
it will very likely work with a 4-line LCD. Because I can't test it, I don't
want to post it here (yet). So I'll send it to you in a PM on Wednesday.
Look for it in your PM inbox
------------

Update:
I later created a tested, working 20x4 flexible LCD driver.
It's posted in the CCS Code Library at the following link:
http://www.ccsinfo.com/forum/viewtopic.php?t=28268

------
Edited to add a link to the 20x4 driver.

The Puma · Joined: 23 Apr 2004 Posts: 227 Location: The Netherlands

specialk · Joined: 12 Nov 2005 Posts: 27

Just change this:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

That's not sufficient. The LCD420.C file has a "lcdline" variable
which must be added to my driver, and the "case '\n'" statement
must be modified to increment that variable. Also, CCS doesn't
initialize "lcdline" to 1, so that should be done.

As I said, I did not post the modified driver because I haven't tested it
in hardware.

I'm not going to PM any more copies of the modified driver.
The two people who requested it have not even looked in their PM
boxes yet.

If you want to post a driver for them, go ahead.

The Puma · Joined: 23 Apr 2004 Posts: 227 Location: The Netherlands

@PCM programmer

Thx PCM for the driver,
i will post the result later this week

sonicdeejay · Joined: 20 Dec 2005 Posts: 112

dear PCM programmer,

will the driver works on 2x20 matrix with Hitachi's LCD HD44780 module???

this code has to be insert in my main program or call as #include(flexlcd.c) ????

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

sonicdeejay · Joined: 20 Dec 2005 Posts: 112

Since my PIC18F2525 is used port B for LCD,I change this in the driver code,,,

The Puma · Joined: 23 Apr 2004 Posts: 227 Location: The Netherlands

Can this driver also used for 4x20 lcd's?

My evaulation board has the following connection
enable - RB1
rs - RB2
RW - RB3
D4 - RB4
D5 - RB5
D6 - RB6
D7 - RB7

But i must connect D6 and D7 to another poort pin

This pins did not work together with the ICD2 programmer debugger
This programmer use also port rb 6 and rb7

Can this lcd driver used for this configuration?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

The Puma · Joined: 23 Apr 2004 Posts: 227 Location: The Netherlands

Driver works now for 20x4 lcd

But there are some things with the gotoxy command

Can you Update this driver with the following things if possible
Cursor Blink, Custum caracter And more ....

The Puma · Joined: 23 Apr 2004 Posts: 227 Location: The Netherlands

I have modified the driver

It use not blink, cursor and custum chars
Any comments and modifications are welcome

////////////////////////////////////////////////////////////////////////////
//// FLEX_LCD420.C ////
//// Driver for common 4x20 LCD modules ////
//// ////
//// lcd_init() Must be called before any other function. ////
//// ////
//// lcd_putc(c) Will display c on the next position of the LCD. ////
//// The following have special meaning: ////
//// \f Clear display ////
//// \n Go to start of second line ////
//// \b Move back one position ////
//// \c Cursor on ////
//// \d Blink character ////
//// \1 Custom character DegC ////
//// ////
//// lcd_gotoxy(x,y) Set write position on LCD (upper left is 1,1) ////
//// ////
//// lcd_getc(x,y) Returns character at position x,y on LCD ////
//// ////
////////////////////////////////////////////////////////////////////////////
//// (C) Copyright 1996,1997 Custom Computer Services ////
//// This source code may only be used by licensed users of the CCS C ////
//// compiler. This source code may only be distributed to other ////
//// licensed users of the CCS C compiler. No other use, reproduction ////
//// or distribution is permitted without written permission. ////
//// Derivative programs created using this software in object code ////
//// form are not restricted in any way. ////
////////////////////////////////////////////////////////////////////////////

// These pins are for the PIC development board:
// B1 enable
// B2 rs
// B3 rw
// B4 D4
// B5 D5
// E1 D6
// E0 D7

#define LCD_E PIN_B1
#define LCD_RS PIN_B2
#define LCD_RW PIN_B3
#define LCD_DB4 PIN_B4
#define LCD_DB5 PIN_B5
#define LCD_DB6 PIN_E1
#define LCD_DB7 PIN_E0

// Clear and home
#define LCD_CLR_DISP 0x01 // Clear screen, home cursor, unshift display
#define LCD_RETURN_HOME 0x02 // Home cursor, unshift display

// Set entry mode: display shift on/off, dec/inc cursor move direction
#define LCD_ENTRY_DEC 0x04 // Display shift off, dec cursor move dir
#define LCD_ENTRY_DEC_SHIFT 0x05 // Display shift on, dec cursor move dir
#define LCD_ENTRY_INC 0x06 // Display shift off, inc cursor move dir
#define LCD_ENTRY_INC_SHIFT 0x07 // Display shift on, inc cursor move dir

// Display on/off, cursor on/off, blinking char at cursor position
#define LCD_DISP_OFF 0x08 // Display off
#define LCD_DISP_ON 0x0C // Display on, cursor off
#define LCD_DISP_ON_BLINK 0x0D // Display on, cursor off, blink char
#define LCD_DISP_ON_CURSOR 0x0E // Display on, cursor on
#define LCD_DISP_ON_CURSOR_BLINK 0x0F // Display on, cursor on, blink char

// Move cursor/shift display
#define LCD_MOVE_CURSOR_LEFT 0x10 // Move cursor left (decrement)
#define LCD_MOVE_CURSOR_RIGHT 0x14 // Move cursor right (increment)
#define LCD_MOVE_DISP_LEFT 0x18 // Shift display left
#define LCD_MOVE_DISP_RIGHT 0x1C // Shift display right

// Function set: set interface data length and number of display lines
#define LCD_FUNCTION_4BIT_1LINE 0x20 // 4-bit interface, single line, 5x7 dots
#define LCD_FUNCTION_4BIT_2LINES 0x28 // 4-bit interface, dual line, 5x7 dots
#define LCD_FUNCTION_8BIT_1LINE 0x30 // 8-bit interface, single line, 5x7 dots
#define LCD_FUNCTION_8BIT_2LINES 0x38 // 8-bit interface, dual line, 5x7 dots

#define LCD_CGRAM_BASE_ADDR 0x40 // Set the CGRAM address
#define LCD_DDRAM_BASE_ADDR 0x80 // Set the DDRAM address

// Address positions
#define LCD_LINE_1 0x80 // Position of start of line 1
#define LCD_LINE_2 0xC0 // Position of start of line 2
#define LCD_LINE_3 0x94 // Position of start of line 3
#define LCD_LINE_4 0xD4 // Position of start of line 4

#define LCD_DEGREE_CHAR 0x00 // Ascii 00

#define lcd_type 2 // 0=5x7, 1=5x10, 2=2 lines

BYTE const LCD_INIT_STRING[4] = {
LCD_FUNCTION_4BIT_2LINES | (lcd_type << 2), // Set mode: 4-bit, 2 lines, 5x7 dots
LCD_DISP_ON,
LCD_CLR_DISP,
LCD_ENTRY_INC };

BYTE const LCD_CUSTOM_CHARS[] = {
0x1C,0x14,0x1C,0x00,0x00,0x00,0x00,0x00, // DegC
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F, // Not used
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F, // Not used
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F, // Not used
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F, // Not used
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F, // Not used
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F, // Not used
0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F }; // Not used

BYTE lcd_line;

BYTE lcd_read_nibble() {
BYTE retval;

#bit retval_0 = retval.0
#bit retval_1 = retval.1
#bit retval_2 = retval.2
#bit retval_3 = retval.3
retval = 0;
output_high(LCD_E);
delay_cycles(1);
retval_0 = input(LCD_DB4);
retval_1 = input(LCD_DB5);
retval_2 = input(LCD_DB6);
retval_3 = input(LCD_DB7);
output_low(LCD_E);
return(retval);
}

BYTE lcd_read_byte() {
BYTE low,high;

output_high(LCD_RW);
delay_cycles(1);
high = lcd_read_nibble();
low = lcd_read_nibble();
return((high << 4) | low);
}

void lcd_send_nibble( BYTE n ) {
output_bit(LCD_DB4, !!(n & 1));
output_bit(LCD_DB5, !!(n & 2));
output_bit(LCD_DB6, !!(n & 4));
output_bit(LCD_DB7, !!(n & 8));
delay_cycles(1);
output_high(LCD_E);
delay_us(2);
output_low(LCD_E);
}

void lcd_send_byte( BYTE address, BYTE n ) {
output_low(LCD_RS);
while (bit_test(lcd_read_byte(),7)); // wait until busy flag is low
if (address)
output_high(LCD_RS);
else
output_low(LCD_RS);
delay_cycles(1);
output_low(LCD_RW);
delay_cycles(1);
output_low(LCD_E);
lcd_send_nibble(n >> 4);
lcd_send_nibble(n & 0xf);
}

void lcd_init() {
BYTE i;

lcd_line = 1;
output_low(LCD_RS);
output_low(LCD_RW);
output_low(LCD_E);
delay_ms(15);
for (i=1;i<=3;++i) {
lcd_send_nibble(3);
delay_ms(5);
}
lcd_send_nibble(2);
for (i=0;i<=sizeof(LCD_INIT_STRING);++i)
lcd_send_byte(0, LCD_INIT_STRING[i]);
}

void lcd_init_custom_chars() {
BYTE i;

lcd_send_byte(0,LCD_CGRAM_BASE_ADDR);
for (i=0;i<64;i++) {
lcd_send_byte(1,LCD_CUSTOM_CHARS[i]);
delay_ms(2);
}
}

void lcd_gotoxy( BYTE x, BYTE y ) {
BYTE address;

switch(y) {
case 1 : address=LCD_LINE_1; break;
case 2 : address=LCD_LINE_2; break;
case 3 : address=LCD_LINE_3; break;
case 4 : address=LCD_LINE_4; break;
}
address+=x-1;
lcd_send_byte(0,0x80 | address);
}

void lcd_putc( char c ) {
switch(c) {
case '\f' : lcd_send_byte(0,LCD_CLR_DISP);
lcd_line=1;
delay_ms(2); break;
case '\n' : lcd_gotoxy(1,++lcd_line); break;
case '\b' : lcd_send_byte(0,LCD_MOVE_CURSOR_LEFT); break;
case '\c' : lcd_send_byte(0,LCD_DISP_ON_CURSOR); break;
case '\d' : lcd_send_byte(0,LCD_DISP_ON_BLINK); break;
case '\1' : lcd_send_byte(1,LCD_DEGREE_CHAR); break;
default : lcd_send_byte(1,c); break;
}
}

char lcd_getc( BYTE x, BYTE y ) {
char value;

lcd_gotoxy(x,y);
while (bit_test(lcd_read_byte(),7)); // wait until busy flag is low
output_high(LCD_RS);
value = lcd_read_byte();
output_low(LCD_RS);
return(value);
}