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Problems with LCD driver

 
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Ares
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Problems with LCD driver
PostPosted: Wed May 12, 2004 4:41 pm     Reply with quote

I have this code in a test program,but it doesn't work,leds don't shine.Port B is configured in the "LCD.c" archive as output for the LCD,but LCD it is not conected because i haven't any.Could it be that the problem?."LCD.c" arhive is the one on the original CCS PIC C Compiler progam,any change was made.

Thank you for your help.

#include <16F877.h>
#use delay(clock=4194304)
#fuses HS, NOWDT, NOPROTECT, NOPUT, NOBROWNOUT, NOLVP
#byte port_c=7
#define led1 PIN_C2
#define led2 PIN_C3
#include <lcd.c>

void main()
{

lcd_init();
set_tris_c(0x00);
port_c=0;
lcd_putc("Look this leds");

do
{
output_high(led1);
output_low(led2);
delay_ms(3000);


output_low(led1);
output_high(led2);
delay_ms(3000);


}while(true);


}
Haplo



Joined: 06 Sep 2003
Posts: 659
Location: Sydney, Australia

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PostPosted: Wed May 12, 2004 5:22 pm     Reply with quote

When you debug the code, does it get passed lcd_init()? What happend when you comment that line?
Ares
Guest







PostPosted: Thu May 13, 2004 8:28 am     Reply with quote

Haplo wrote:
When you debug the code, does it get passed lcd_init()? What happend when you comment that line?


If I comment this lines:

lcd_init();
lcd_putc("whatever");

the rest of the program works well,that is,LEDs shine.I supose that if i had the LCD conected,program would work properly.The problem is that I can't find why it doesn't work without it.Any signal is sent from the LCD to the PIC ,at least I don't see anything in the "LCD.c" program,so I don't know if it really will work when It will be connected.
Thank you again for your help.
C-H Wu
Guest







the 'while loop' in lcd.c
PostPosted: Thu May 13, 2004 9:07 am     Reply with quote

All your problems comes from the following line in lcd_send_byte() of CCS's driver, LCD.C:

while ( bit_test(lcd_read_byte(),7) );

if your LCD is not connected, then you will end up hanging in the while loop. I modified it with a timeout break like this

while ( bit_test(lcd_read_byte(),7) )
{
delay_us ( 5 );
if ( --i == 0 )
{
lcd_fail = TRUE;
break;
}
}

such that I can live with, or without, the LCD, or, with a dead LCD.

best wishes
djpark



Joined: 02 Mar 2004
Posts: 49

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Re: Problems with LCD driver
PostPosted: Thu May 13, 2004 11:30 am     Reply with quote

Ares wrote:
I have this code in a test program,but it doesn't work,leds don't shine.Port B is configured in the "LCD.c" archive as output for the LCD,but LCD it is not conected because i haven't any.Could it be that the problem?."LCD.c" arhive is the one on the original CCS PIC C Compiler progam,any change was made.


"C-H Wu" has pointed out the correct hanging problem with stock LCD driver without a real LCD. Like him, I, too, use similar 2sec timeout routine in the status return function.

I also added a 4.7K register to the LCD panel bit7 to ground which will pull the status low if the port is read back, so that my LCD routine can read the pin status before init or write and if it is high (pulled up by 100k on PIC side), I consider the LCD is not connected. When it is connected back (status is low), I do lcd_init() again before further write.

It works like a magic. You can pull out and plug back the LCD panel and watch the LCD screen pop up correctly again.

-- dj
Ares
Guest







Thanks
PostPosted: Thu May 13, 2004 4:15 pm     Reply with quote

Thank you,both of you for your help.I really feel more calmed now I know wich the problem was.I hope it will work with the LCD....hehehe.
Best wishes
Guest








PostPosted: Thu May 13, 2004 5:09 pm     Reply with quote

try sticking in the following

printf(lcd_putc,"whatever");
RatFink



Joined: 01 May 2004
Posts: 49

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PostPosted: Fri May 14, 2004 12:32 am     Reply with quote

I also have trouble with this driver using it with a crystalfontz LCD. I don't understand why they would make it use the Port B knowing that it cause problem with the ICD.
MGP



Joined: 11 Sep 2003
Posts: 57

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PostPosted: Fri May 14, 2004 7:31 pm     Reply with quote

RatFink wrote:
I also have trouble with this driver using it with a crystalfontz LCD. I don't understand why they would make it use the Port B knowing that it cause problem with the ICD.


Because it's an older driver that's been around long before the ICD and on-chip debugging existed.

Most everyone that's been using CCS C for a while and uses the LCD driver library has changed it to fit their own requirements or written their own (that's what I did).
RatFink



Joined: 01 May 2004
Posts: 49

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PostPosted: Fri May 14, 2004 7:37 pm     Reply with quote

MGP wrote:
RatFink wrote:
I also have trouble with this driver using it with a crystalfontz LCD. I don't understand why they would make it use the Port B knowing that it cause problem with the ICD.


Because it's an older driver that's been around long before the ICD and on-chip debugging existed.

Most everyone that's been using CCS C for a while and uses the LCD driver library has changed it to fit their own requirements or written their own (that's what I did).


Is there someplace I could find one of these drivers. I know very little C language, my schooling is in Electronics but I've managed to get all my code to work except for the LCD.
Mc



Joined: 07 May 2004
Posts: 11

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PostPosted: Sat May 15, 2004 4:04 am     Reply with quote

I use an adaptation of this one:

http://www.vermontficks.org/lcdd.htm


Have a look Wink
Guest








PostPosted: Sat May 15, 2004 4:49 pm     Reply with quote

if your using the icd development board heres the reason why it does't work.

*********************************************************
Brian,

The pins 39 and 40 are not connected on the board other than to the ICSP socket since these pins need to be isolated during in-circuit programming.
Circuitry on these pins can cause corruption of the programming bitstream and clock. It may be possible to use the CCS complier's LCD functions with another port, however we are not familiar with the LCD section of the CCS compiler.

Best Regards,

UK Techhelp

INTERNET ACCESS
World Wide Web address -http://www.microchip.com/
FTP address - ftp://ftp.microchip.com/
*************************************************************
i have some source code which use port D, you can download it here:
(i didn't write them, but have used them and they work fine)

http://home.t-online.de/home/Matthias.Stehr/hoehe.htm
RatFink



Joined: 01 May 2004
Posts: 49

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PostPosted: Sat May 15, 2004 7:57 pm     Reply with quote

Mc wrote:
I use an adaptation of this one:

http://www.vermontficks.org/lcdd.htm


Have a look Wink


I tried that one and couldn't make it work, but I did find one here that worked real easy for me (Though I would rather not have the control bits on port A) I posted it in the code library because out of all of them I've tried, this one just worked.
young



Joined: 24 Jun 2004
Posts: 285

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PostPosted: Tue Jun 29, 2004 2:44 pm     Reply with quote

I used C-H Hu and Djpark's method modified ares's program, however, I did not got the lcd display characters, but the rb7 led turns on. what is wrong with my code. my hardware is 26f877a, lcd connected to portb and every connection comes from the easy2 board, I did not change anything? advice please, and I also post the testing file provided by ares at "2X16 LCD on pic16f877a portb" post.

Thanks
[/code]
E YILMAZ
Guest







for modification...
PostPosted: Sat Jun 04, 2005 11:19 am     Reply with quote

Thank you C-H Hu!
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