LCD won't display?

MrDEB · Jul 21, 2011

wondering if its in the code is the problem?
using a hd44780 but no display.
The backlight lights up, screen seems to flicker.
Adjusted the pot but no display
any suggestions?

Code:

Device = 18F2420
Clock = 20 // 
//Config OSC = INTIO2

// some LCD options...
#option LCD_DATA = PORTB.0              // Assign the LCD connections
#option LCD_EN = PORTC.6                //
#option LCD_RS = PORTC.5                //

// import LCD library...
//Include "InternalOscillator.bas "
Include "LCD.bas"
Include "convert.bas"
Dim Variable As Word

// Start Of Program...
DelayMS(550)                            // Let the LCD warm up
LCD.Cls                                 // Clear the LCD screen
LCD.WriteAt(1,1,"Hello World")
                                             // Send some text to the LCD
Variable = 0                            // Clear the "Variable" register
While True
   Inc(Variable)                       // Increment the "Var1" register
    // Convert to a string,
    //  and always display 5 characters   
    LCD.WriteAt(2,1,Convert.DecToStr(Variable,5))   
   
  DelayMS(1000)                       // Delay for 1 second                 
Wend

need to locate schematic if needed? basic 4 data lines connections.
Tried changing the C6 C5 to C5 C6

Mike - K8LH · Jul 21, 2011

Hi MrDeb,

Is there an LCD.Init function that needs to be called?

be80be · Jul 21, 2011

Portb is Analog You need a ADCON1 =%00001111 in there if you want to use a LCD data on portB

Mike this Inits the LCD Include "LCD.bas" but for some reason it doesn't set port pins right on all chips.

This should work

Code:

Device = 18F2420
Clock = 20 // 

 
// some LCD options...
#option LCD_DATA = PORTB.0              // Assign the LCD connections
#option LCD_EN = PORTC.6                //
#option LCD_RS = PORTC.5                //
 
// import LCD library...
Include "LCD.bas"
Include "convert.bas"
Dim Variable As Word
 
// Start Of Program...
ADCON1 = %00001111  //All digital
DelayMS(550)                            // Let the LCD warm up
LCD.Cls                                 // Clear the LCD screen
LCD.WriteAt(1,1,"Hello World")
                                             // Send some text to the LCD
Variable = 0                            // Clear the "Variable" register
While True
   Inc(Variable)                       // Increment the "Var1" register
    // Convert to a string,
    //  and always display 5 characters   
    LCD.WriteAt(2,1,Convert.DecToStr(Variable,5))   
 
  DelayMS(1000)                       // Delay for 1 second                 
Wend

MrDEB · Jul 22, 2011

Thanks Burt
I was wondering if perhaps that there was something about the port setup seeing how I tried this same code on two different Pics.
Will give it a try
THANKS again.

be80be · Jul 22, 2011

The code works I tested it on hardware so if you can't get it going you have a hardware problem

MrDEB · Jul 22, 2011

It should work but it dosn't.
When I get back from the fair grounds tonight going to recheck my wiring but trying out using two different pica
2420 and a 4520
also going to try a different LCD display.
Looking at the C port as well

be80be · Jul 22, 2011

There not any thing wrong with PORTC it's I/O only

You hook the LCD up like this

Portb.0 to lcd data4
Portb.1 to lcd data5
Portb.2 to lcd data6
Portb.3 to lcd data7
LCD_RS to PORTC.5
LCD_EN to PORTC.6
LCD_VO to a pot center tap top a VDD and Bottom at GND
LCD_VSS to GND
LCD_VDD to 5 volt
LCD_backlite A to 5 volts
LCD_backlite K to GND may need a 120 ohm resistor some have one on the LCD

And gnd the unused pins RW, Data0, Data1, Data2, Data3.

be80be · Jul 22, 2011

Here you something to go by

**broken link removed**

MrDEB · Jul 22, 2011

Only difference I have is a 330 ohm resistor on pin 15 and the unused data pins are not connected to anything.
I have had this display working along time ago.
This is frustrating. Its got to be something simple?
second look? you have B.0, B1, B3, B4
what happened to B.2--mistype??

be80be · Jul 22, 2011

Mistype sorry.
Most of the lcd that have back lights don't even need a resistor there on the LCD but i would check to make sure any way.

If the code I posted doesn't run you have a hardware problem some where. It runs find I did try it. With pic and LCD.

I have had some problems with cheap trimpots from radio shack there easy to turn past the stop and it breaks them.

I always use portb.4 and up I should of looked over that post I fixed it have re looke

MrDEB · Jul 22, 2011

I may have located problem Should the E pin change voltages. I get a constant 4.7 aprox
The RS pin shows 2.? mv
will re verify as I got dinner to get to cooking before the boss gets home!!
YEKS its 508pm

be80be · Jul 22, 2011

E gos low and high but it is fast you'll not see it with DVM I redid this it was kind of fast and I had Vdd on bottom and grd on top but it's not showing as planed
so have a look agin
**broken link removed**

MrDEB · Jul 22, 2011

Tomorrow I am going to pull the PIC out and using a DMM, check that each pin that is supposed to be connected is connected to its proper LCD point.
Been checking using DMM but testing just the plug/ribbon cable/plug/LCD pins.
Perhaps a pin on the LCD header is not correct or not soldered correctly?
Checking and REchecking hardware from point A to point D and everything in between.

MrDEB · Jul 23, 2011

Tested everything but still?
My next trick is --start over. Build a new LCD board then start from scratch

be80be · Jul 23, 2011

If you look at post 12 and some one don't remove the Picture of the SCH I cleared it up a little there is some good info that 3v0 posted here to https://www.electro-tech-online.com/threads/links-character-lcds-tutorials-and-info.112077/

be80be · Jul 24, 2011

MrDeb I did this last night have a look it's a simple board you should make one something like this.
It will save you some headaches

MrDEB · Jul 24, 2011

Here is my simple board

Been using this board as well as the Tap-28.
Very simple but it works (I think my LCD woes are between the board and the LCD)
Using the Tap-28 I need a bunch of jumpers. Been contemplating using the Junebug to test the LCD.
This simple board has provision for testing port outputs (8 LEDs ( 4=LOW and 4=HIGH)
An LCD header
a UART switch that I have to get the bugs out of?)
I will copy schematic if I get time?

MrDEB · Jul 24, 2011

schematic of dev board

Here is my latest design
Very easy

MrDEB · Jul 24, 2011

I need to find out how to get a bigger image using Paint

ericgibbs · Jul 24, 2011

MrDEB said:
I need to find out how to get a bigger image using Paint

hi,
Post the actual Paint file.

LCD won't display?

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