2x16 lcd problem

Printable View

- 28th October 2008, 16:30
k3v1nP

1 Attachment(s)

2x16 lcd problem

After searching the forum for 2x16 I still can't see what my problem is. I have a 2x16 lcd connected to a 16f877a and it only displays solid boxes on the first row. The code I'm using works fine on my Lab-x1 with the 2x20 lcd and I've wired the 2x16 to the 16f877a the same way it is on the Lab-x1. This is the datasheet for the 2x16 i'm using http://www.lcdmk.com/product/zfx/RT162-7.PDF . I think there is something in the DEFINE's that I need to change for this particular display just not sure what. Also pretty sure I've got the BL and the contrast set to readable levels using a couple resistors.

here's my code

Code:

CLEAR ;Define LCD registers and control bits DEFINE OSC 4 ;System speed DEFINE LCD_DREG PORTD ;data register DEFINE LCD_BITS 4 ;width of data path DEFINE LCD_DBIT 4 ;data starts on bit 4 DEFINE LCD_RSREG PORTE ;select register DEFINE LCD_RSBIT 0 ;select bit DEFINE LCD_EREG PORTE ;enable register DEFINE LCD_EBIT 1 ;enable bit DEFINE LCD_RWREG PORTE ;read/write register DEFINE LCD_RWBIT 2 ;read/write bit LOW PORTE.2 ;LCD R/W low (write) We will do no reading DEFINE LCD_LINES 2 ;lines in display DEFINE LCD_COMMANDUS 2000 ;delay in micro seconds DEFINE LCD_DATAUS 20 ;delay in micro seconds ; ;Set the port directions. We are setting (must set) all of PORTD and all of PORTE as outputs ;even though PORTE has only 3 lines. The other 5 lines will be ignored by the system. ; TRISD = %00000000 ; set all PORTD lines to output TRISE = %00000000 ; set all PORTE lines to output ; Set the Analog to Digital control register ADCON1=%00000111 ; needed for the 16F877A see note above and below ; LOOP: ; The main loop of the program LCDOUT $FE, 1 ; clear screen PAUSE 500 ; pause 0.25 seconds LCDOUT "HELLO" ; print LCDOUT $FE, $C0 ; goto second line, first position LCDOUT "WORLD" ; print PAUSE 250 ; pause 0.25 seconds GOTO LOOP ; repeat END ; always end all programs with an END statement

The attached file is basically how I have it wired. Does not show the resistors on the bl and contrast.
Suggestions anyone?
- 28th October 2008, 16:45
skimask

Code:

DEFINE LCD_DATAUS 20 ;delay in micro seconds

Turn that up to about 200 for starters, then after it's working dial it down until it fails again, then dial it back up and add a bit of a fudge factor to keep it working. The LCD needs time to work. Also, add about a one second pause before your first initial LCDOUT command. The LCDOUT needs time to start up.
- 28th October 2008, 16:55
mackrackit

And...

You may want to use a pot on pin #3 of the LCD so it can be adjusted.

Quote:

I have a 2x16 lcd connected to a 16f877a and it only displays solid boxes on the first row.
- 28th October 2008, 16:58
k3v1nP

tried it

Still the same went as high as 500. Also put in a PAUSE of 900 before first lcd out. I don't think it can be a busted lcd cause i have 4 and they all do the same thing. Unless this model is just junk.
- 28th October 2008, 17:00
k3v1nP

Also I can replace the lcd with 8 led's and make them flash, so pretty sure the rest of my circuit is working ok.
- 28th October 2008, 17:05
mister_e

On your schematic, your pinout seems to be wrong... at least the way you connect your Data lines to your PIC.
- 28th October 2008, 17:06
k3v1nP

Quote:

Originally Posted by mackrackit

And...

You may want to use a pot on pin #3 of the LCD so it can be adjusted.

Just put in a 10k pot and I can adjust the crap out of it ... still not displaying any text #$%#!#@$%^
- 28th October 2008, 17:07
skimask

Quote:

Originally Posted by k3v1nP

Still the same went as high as 500. Also put in a PAUSE of 900 before first lcd out. I don't think it can be a busted lcd cause i have 4 and they all do the same thing. Unless this model is just junk.

DATAUS is a byte value. Go to 500, and you may as well go to 244 (figured this out the hard way awhile back, not mentioned in the book, but good to know).
Try the pause value up to a couple of seconds...some really are that slow...
Also, double, nay, triple check your wiring...Make sure you've got the connector on the 'right way'.
And put a 'heartbeat LED' in there...

Code:

CLEAR ;Define LCD registers and control bits DEFINE OSC 4 ;System speed DEFINE LCD_DREG PORTD ;data register DEFINE LCD_BITS 4 ;width of data path DEFINE LCD_DBIT 0 ;data starts on bit 0 DEFINE LCD_RSREG PORTE ;select register DEFINE LCD_RSBIT 0 ;select bit DEFINE LCD_EREG PORTE ;enable register DEFINE LCD_EBIT 1 ;enable bit DEFINE LCD_RWREG PORTE ;read/write register DEFINE LCD_RWBIT 2 ;read/write bit LOW PORTE.2 ;LCD R/W low (write) We will do no reading DEFINE LCD_LINES 2 ;lines in display DEFINE LCD_COMMANDUS 4000 ;delay in micro seconds DEFINE LCD_DATAUS 200 ;delay in micro seconds ; ;Set the port directions. We are setting (must set) all of PORTD and all of PORTE as outputs ;even though PORTE has only 3 lines. The other 5 lines will be ignored by the system. ; TRISD = %00000000 ; set all PORTD lines to output LED VAR PORTD.7 OUTPUT LED TEMP VAR BYTE TRISE = %00000000 ; set all PORTE lines to output ; Set the Analog to Digital control register ADCON1=%00000111 ; needed for the 16F877A see note above and below ; PAUSE 2000 LOOP: ; The main loop of the program TEMP = TEMP + 1 LED = TEMP.0 LCDOUT $FE, 1 ; clear screen PAUSE 500 ; pause 0.25 seconds LCDOUT "HELLO" ; print LCDOUT $FE, $C0 ; goto second line, first position LCDOUT "WORLD" ; print PAUSE 250 ; pause 0.25 seconds GOTO LOOP ; repeat END ; always end all programs with an END statement

EDIT: Oh yeah, that schematic is jacked up...
Example schematic and/or program is in the PBP manual...
- 28th October 2008, 17:08
mister_e

As it is connected right now i would try

Code:

DEFINE LCD_DREG PORTD ;data register DEFINE LCD_BITS 4 ;width of data path DEFINE LCD_DBIT 0

AND change the DATAUS as Skimask said.
- 29th October 2008, 04:22
k3v1nP

So i ripped my circuit down and simplified it with a 16f84a and that worked with all my lcd's. Rebuilt it with the 16f877a and it now works as well. I must have had something messed up in the first build. Sometimes I guess it just pays to start from scratch.

Thanks to everyones for there help. One thing for sure I am certainly learning alot.
- 29th October 2008, 04:34
skimask

Quote:

Originally Posted by k3v1nP

So i ripped my circuit down and simplified it with a 16f84a and that worked with all my lcd's. Rebuilt it with the 16f877a and it now works as well. I must have had something messed up in the first build. Sometimes I guess it just pays to start from scratch.
Thanks to everyones for there help. One thing for sure I am certainly learning alot.

Good game... Any idea what the real problem was? Miswired? One wire off?
Keep in mind, the PBP manual, while not a 'do-all end-all of manuals', has a lot of good information in it, a lot of it 'in between the lines', and a lot of it applies to this PIC and that PIC since they're all pretty much built on the same architecture. Use it and use it often! It'll save you a lot of time and trouble. Same goes for the PIC datasheets. A load of the problems that show up here could have been avoided by those two items.
- 30th October 2008, 04:46
k3v1nP

Not a hundred % sure but it was probably just a wrong wire or 2. Wiring diagrams are usually pretty much straight forward so I usually just slap them together and they work ... if I get lucky. When they don't work I can look at it a hundred times and it looks absolutely right. Howerver it only takes one mistake to F it all up. So when things don't work I usually make the call that its one or the other (software or hardware)... this time I think I made the wrong choice. When I rebuilt the circuit this last time I was absolutely maticulous and took my time ... and it works.
Thanks again for the help next time I should just post photographs cause probably all I needed was a second pair of eyes to have a look at it. Now that I got my lcd's all working on to the next challenge. ( I totally understand mister_e's avatar now).