Flexible LCD driver

hadeelqasaimeh · Joined: 05 Jan 2006 Posts: 105

hi pcm

i wonder if i can use PIN A4 and PIN A5 as independent input or output
i try but it not work independently
thank you

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

You didn't post the PIC that you're using. When you have a hardware-
specific question, you should post the PIC type.

On many PICs, the pin driver for Pin A4 is "open drain". It doesn't have
the ability to drive the pin to a high level. It can only drive it to a low
level. If you set the pin to be at a high level with the output_high()
function, the output will be "floating". You can fix this by adding an
external pull-up resistor to the pin. You can use 4.7K.

On some PICs, pin A5 is an "input only" pin. It doesn't have the
ability to drive the output in any way. So it can't be used with the
Flex LCD driver.

hadeelqasaimeh · Joined: 05 Jan 2006 Posts: 105

i use 16f877a

applecon2000 · Joined: 29 Jul 2007 Posts: 31 Location: UK

Dear sir, can you explain the following code in LCD.C
"void lcd_init(void)
{
int8 i;

output_low(LCD_RS);

#ifdef USE_LCD_RW
output_low(LCD_RW);
#endif

output_low(LCD_E);

delay_ms(15);

for(i=0 ;i < 3; i++)
{
lcd_send_nibble(0x03);
delay_ms(5);
}

lcd_send_nibble(0x02);

for(i=0; i < sizeof(LCD_INIT_STRING); i++)
{
lcd_send_byte(0, LCD_INIT_STRING[i]);

// If the R/W signal is not used, then
// the busy bit can't be polled. One of
// the init commands takes longer than
// the hard-coded delay of 60 us, so in
// that case, lets just do a 5 ms delay
// after all four of them.
#ifndef USE_LCD_RW
delay_ms(5);
#endif
}

}
"
i do not understand the meaning of "for(i=0 ;i < 3; i++)
{
lcd_send_nibble(0x03);
delay_ms(5);
}

lcd_send_nibble(0x02);

for(i=0; i < sizeof(LCD_INIT_STRING); i++)
{
lcd_send_byte(0, LCD_INIT_STRING[i]);
"
why we need to set those parameters for LCD initialization?
please explain the purpose for me
I do thank you for your reply.
_________________
Enjoy our EEE

applecon2000 · Joined: 29 Jul 2007 Posts: 31 Location: UK

for my question shown above:
Could u just explain the meaning of the code :for(i=0 ;i < 3; i++)
{
lcd_send_nibble(0x03);
delay_ms(5);
}

lcd_send_nibble(0x02);

......................................#
what's the purpose of first "for(i=0 ;i < 3; i++)" and the code of "lcd_send_nibble(0x02); "
thanks a lot and sorry about my previous problem
_________________
Enjoy our EEE

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

You need to use http://www.google.com to search for articles on
how to use an LCD.

For example, search using Google for:

pokiko · Joined: 27 Jul 2007 Posts: 33

Could you give an example for 4 bit LCD by using flexlcd driver and pic18f2520 for hd44780 16x2 LCD which will write to screen just "hello". The pin congiguration have to be as follows.

LCD PIC

D7 -- RB7
D6 -- RB6
D5 -- RB5
D4 -- RB4
E -- RB3
RS -- RB2

RW is grounded. PIC's RB0 and RB1 is used for another aim. crystal oscillator is 20 MHZ.

what kind of configuration i have to make in driver.
thanks.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

At the start of the Flex_LCD.c file, edit the pin list so it looks like this:

BrunoCF · Joined: 14 Aug 2007 Posts: 2 Location: SP - Brasil

Thank you for the code. Worked just fine for me.

nmeyer · Joined: 09 Jul 2004 Posts: 70

I have purchased the PICDEM 2 PLus board and i am using the Flex_lcd driver for the lcd. However, i am finding that if i try to write more than 7 characters on a line, it locks up the PIC.
#include <18F4520.h>
#device adc=8
#include <stdio.h>
#include <math.h>

#FUSES NOWDT //No Watch Dog Timer
#FUSES WDT128 //Watch Dog Timer uses 1:128 Postscale
#FUSES HS //High speed Osc (> 4mhz)
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOBROWNOUT //No brownout reset
#FUSES BORV25 //Brownout reset at 2.5V
#FUSES NOPUT //No Power Up Timer
#FUSES NOCPD //No EE protection
#FUSES STVREN //Stack full/underflow will cause reset
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOWRT //Program memory not write protected
#FUSES NOWRTD //Data EEPROM not write protected
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES FCMEN //Fail-safe clock monitor enabled
#FUSES PBADEN //PORTB pins are configured as analog input channels on RESET
#FUSES NOWRTC //configuration not registers write protected
#FUSES NOWRTB //Boot block not write protected
#FUSES NOEBTR //Memory not protected from table reads
#FUSES NOEBTRB //Boot block not protected from table reads
#FUSES NOCPB //No Boot Block code protection
#FUSES LPT1OSC //Timer1 configured for low-power operation
#FUSES MCLR //Master Clear pin enabled
#FUSES XINST //Extended set extension and Indexed Addressing mode enabled

#use delay(clock=4000000,RESTART_WDT)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

#include <Flex_LCD>

void main()
{

setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF|ADC_TAD_MUL_0);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_wdt(WDT_OFF);
setup_timer_0(RTCC_INTERNAL);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
while (true)
{
output_low(PIN_B0);
output_low(PIN_B1);
output_low(PIN_B2);
output_low(PIN_B3);
output_low(PIN_C2);
delay_ms(1000);
output_high(PIN_B0);
output_high(PIN_B1);
output_high(PIN_B2);
output_high(PIN_B3);
//output_high(PIN_C2);
delay_ms(1000);
printf("Hello\n\r");
output_high(PIN_D7);
lcd_init();
printf(lcd_putc,"\fRawson\n");
printf(lcd_putc,"Accurat");
}
}
Does anyone have any idea what i am doing wrong?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

nmeyer · Joined: 09 Jul 2004 Posts: 70

Thanks for the input. Do you have any ideas on why i can only do 7 characters?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

1. The 'XINST' fuse could be the cause of it doing only seven characters.
Make sure you change it to 'NOXINST' in all your programs.
It's essential.

2. Post the list of #define statements that show the connections
between the LCD and the PIC. These #define statements are at
the start of the Flex_lcd.c driver, and must match the connections
on your PIC board.

3. Your test program is too complicated. Try a very simple program.
Example:

nmeyer · Joined: 09 Jul 2004 Posts: 70

I changed the setting to NOXINST and it still performed the same. Here are my defines from the flex_lcd file.

// These pins are for the Microchip PicDem2-Plus board,
// which is what I used to test the driver. Change these
// pins to fit your own board.

#define LCD_DB4 PIN_D0
#define LCD_DB5 PIN_D1
#define LCD_DB6 PIN_D2
#define LCD_DB7 PIN_D3

#define LCD_E PIN_D6
#define LCD_RS PIN_D4
#define LCD_RW PIN_D5

// If you only want a 6-pin interface to your LCD, then
// connect the R/W pin on the LCD to ground, and comment
// out the following line.

#define USE_LCD_RW 1

//========================================

#define lcd_type 2 // 0=5x7, 1=5x10, 2=2 lines
#define lcd_line_two 0x40 // LCD RAM address for the 2nd line

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Based on those pin numbers, you are apparently using the new "Rohs
update" version of the PicDem2-Plus board.

That version of the board can be identified by a surface-mount pad
pattern at the bottom of the proto-typing area on the board. The older
version of the board doesn't have that surface-mount area on it.

If you have the new Rohs version of the board you need to use the
test program shown below. Notice how it adds a #define statement
for the LCD power pin, and it adds two new lines at the start of main().
Those lines are essential for the new Rohs version of the PicDem2-Plus.

Here are the pin assignments that you must set at the top of the Flex
driver. Also, for the "Rohs" PicDem2-Plus board, you must comment
out the "#define USE_LCD_RW 1" line, as shown below.