2x16 LCD Module with HD44780 + 16F877A

[comwarrior]

Can someone help me to debug this problem?

Above LCD with above PIC have been conected and programmed...

the LCD displays absolutly nothing not even at power on...
I have purchased two identical and neither display anything at power on...
I have a 38K serial2 going to a com port on my PC which works perfectly...

i'm using all 8 data bits connected to PORT D...
RS (pin 4) is connected to PORTC.5
RW (pin 5) is connected to PORTC.6
E (pin6) is connected to PORTC.7

Contrast is connected to +5V via 1.5K resister

My defines are as follows...

DEFINE LCD_DREG PORTD 'LCD data port
DEFINE LCD_DBIT 0 'LCD data starting bit 0 or 4
DEFINE LCD_RSREG PORTC 'LCD register select port
DEFINE LCD_RSBIT 5 'LCD register select bit
DEFINE LCD_EREG PORTC 'LCD enable port
DEFINE LCD_EBIT 7 'LCD enable bit
DEFINE LCD_RWREG PORTC 'LCD read/write port
DEFINE LCD_RWBIT 6 'LCD read/write bit
DEFINE LCD_BITS 8 'LCD bus size 4 or 8
DEFINE LCD_LINES 2 'Number lines on LCD
DEFINE LCD_COMMANDUS 2000 'Command delay time in us
DEFINE LCD_DATAUS 50 'Data delay time in us

TRISC and D are set to all outputs, i don't know if this is correct or not?

I think their is 'some' activity on the LCD data and controll lines but i only have a digital multimeter so, can't be sure.

I'm using PORTA and E for analogue, PWM 0 and 1 (RC1 and RC2), TMR1 in counter mode using PORTC0 as input and PORTB for digital output and SER2 PC telemetry link...

I have no idea where to begin to find the problem, so any help appreciated...

Thanks

[mackrackit]

Try the contrast like the example in the PBP manual. That is the safest way for unknown displays. Normally the contrast likes a little more - than + .

Another thing to double check is if the data lines are in the correct order when connecting to the PIC.

[comwarrior]

I'll try the contrast in the morning, i think i got a 10K pot somewhere...

I just wrote a simple "hello world" type LCD test program...

I loadedit into oshonsoft's pic simulator and configured it's LCD module...
Acording to the microcontroller view, all the data lines switch to outputs...
However, it gets into a loop with nothing displayed in the LCD module, and tmr1 prescaler is continueously counting up by 1 each loop but over flows without a change in instructions...

:edit after about 17000us in simulation RD0, RD1,RD5 and RD4 to high... still nothing on LCD module

:edit after 22000us in simulation it has now started putting charecters on the LCD...

[mackrackit]

Just for giggles, can we see the whole code?

[comwarrior]

@ device pic16F877A, HS_OSC
@ device WDT_OFF
@ device PWRT_OFF
@ device BOD_OFF
@ device LVP_OFF
@ device WRT_OFF
@ device CPD_OFF
@ device DEBUG_OFF

Define  OSC				4						' Set clock speed
DEFINE  SER2_BITS		8						' Ser2 number of data bits
DEFINE LCD_DREG PORTD		'LCD data port
DEFINE LCD_DBIT 0			'LCD data starting bit 0 or 4
DEFINE LCD_RSREG PORTC		'LCD register select port
DEFINE LCD_RSBIT 5			'LCD register select bit
DEFINE LCD_EREG PORTC		'LCD enable port
DEFINE LCD_EBIT 7			'LCD enable bit
DEFINE LCD_RWREG PORTC		'LCD read/write port
DEFINE LCD_RWBIT 6			'LCD read/write bit
DEFINE LCD_BITS 8			'LCD bus size 4 or 8
DEFINE LCD_LINES 2			'Number lines on LCD
DEFINE LCD_COMMANDUS 2000	'Command delay time in us
DEFINE LCD_DATAUS 50		'Data delay time in us
'Pause 1000

loop:
LCDOUT $FE, 1, 2, "INITIALISING"
LCDOUT $FE, $C0, "Hello"
goto loop

[comwarrior]

Found it... looks like the contrast likes to be fully negative...

Thanks for the help... Iactualy thaught the contrast should be more positive acording to all the scmatics i looked at...

Thanks