Blank LCD Issue - SOLVED!

Testing/Troubleshooting
1

Hi guys,

So I’ve hooked up an OPTREX LCD to my CORE in 4-bit mode, and only the backlight works, theres no pixels.

You can get the datasheet here

The Luminance pot is working fine, but the Contrast pot has no effect whatsoever.

I’m using a SmashTV PIC 18F4685 with MIOS V1.9E preloaded, and i also tried another pic with 1.9F preloaded.

I’m using the optimized c64 PSU circuit, connected to J2 of the core, and got +5V in all the relevant pins in Jim Henry’s guide.

Heres a picture of the problem:

Top side of core (pic 18F removed):

Fig 1: I installed a SIL header to the GND LIFT port, which shouldnt be used.

Fig 2: I installed the voltage regulator to IC3, which isnt used with optimized PSU,

         tried removing it to see if that was the problem, and it wasnt.

Fig 3: When i was installing these 2 caps, i found it really hard to push them in,

          i remember a small piece of ceramic coming off of one of them after trying to force it in.

Note: I do not have midi sockets installed yet.

Core underside:

LCD module:

I installed DIL headers for the 14 holes, including Databus line 0-3, which are not used for 4-bit mode,

and cut these 4 unused cables making sure there was no shorts.

I have checked the wiring about 10 times at this stage and can confirm it is correct.

Here is how i have the LCD wired:

Optrex - Core

1.VSS - VS

2.VCC - VD

3.VEE - V0

4.RS  -  RS

5.RW  -  RW

6.E    -    E

7.D0    -    null

8.D1    -    null

9.D2    -    null

10.D3  -    null

11.D4  -    D4

12.D5  -    D5

13.D6  -    D6

14.D7  -    D7

15.Cathode  -  B-

16.Anode     -  B+

Here is the pinout of the LCD from the datasheet:

I resoldered the pins of J15 but there was no change.

Could someone please give me info in how to check for shorts properly, and which pins to check in particular.

What is the maximum Resistance in Ohms that could indicate a short?

And which pins should i check besides side by side. All 5+ to GND pins im assuming?

btw i definitely have the PIC in the right way when I’m turning on the power.  :wink:

Any help would be appreciated.  :slight_smile:

2

Just guessing..

I see the datasheet does NOT specify how the first 14 pins are numbered.

Are the pin numbers printed on the Circuit board?

I can’t find the datasheet for my own right now, but there is  a drawing of

the pin numbers.

Good Luck,

LyleHaze

3

The contrast pot should always have an effect, especially if V0 outputs 0V.

So long the LCD hasn’t been initialised, you will see a black bar at one line, especially if V0 (contrast voltage) outputs 0V.

You should already see this line if only Vs, Vd and V0 is connected (again: V0 should output 0V, turn the contrast pot accordingly)

Be careful when trying different connections - the LCD can easily be destroyed if Vs/Vd is connected to the wrong pins.

Best Regards, Thorsten.

4

Are the pin numbers printed on the Circuit board?

Yep, pins 1 and 14 are marked on both sides of the LCD

The contrast pot should always have an effect, especially if V0 outputs 0V.

So long the LCD hasn’t been initialised, you will see a black bar at one line, especially if V0 (contrast voltage) outputs 0V.

You should already see this line if only Vs, Vd and V0 is connected (again: V0 should output 0V, turn the contrast pot accordingly)

Be careful when trying different connections - the LCD can easily be destroyed if Vs/Vd is connected to the wrong pins.

Best Regards, Thorsten.

Thanks for the reply TK.

I might try just connecting Vs, Vd and V0 on their own, with the other connections taped individually to prevent the risk of a short, and i will update as to how i got on.

Might be a day or so by time i get to though.

5

If only 1 and 14 are marked, there are two ways you might interpret it.

Could be:

1  2  3  4  5  6  7

8  9 10 11 12 13 14

or

1  3  5  7  9 11 13

2  4  6  8 10 12 14

Notice that both have 1 and 14 in the same place.

I need to find my PDF file for my display.

This page offers some comments on it.

http://www.geocities.com/p9019/lcd.html

Have Fun,

LyleHaze

6

If only 1 and 14 are marked, there are two ways you might interpret it.

Could be:

1  2  3  4  5  6  7

8  9 10 11 12 13 14

or

1  3  5  7  9 11 13

2  4  6  8 10 12 14

Notice that both have 1 and 14 in the same place.

I need to find my PDF file for my display.

This page offers some comments on it.

http://www.geocities.com/p9019/lcd.html

Have Fun,

LyleHaze

LYLE!

I could kiss you man!

Im so stupid i cannot believe it.

I remember reading nebulas post about the pinout in the bulk order, but still managed to read it wrong myself!

Here’s his post on the pinout:

http://www.midibox.org/forum/index.php/topic,9910.msg75364.html#msg75364

I still managed to read the pinout the wrong way as in:

1  8 

2  9

3  10

4  11

5  12

6  13

7  14

I cant believe i made this mistake even after reading that post!  :-[

I also cant wait to rewire the LCD correctly, wether its dead or not, i dont care, at least ive found a reason why.

Funny how i failed to spot this sober, and managed to realise it after reading your post after a few drinks!  :wink:

Thanks man!

7

21:00 Smithy: i have an lupcd hooked upto the core,and all im getting is the backlight, no pixels what so ever

21:02 nILS: […] check the wiring

:wink:

8

LYLE!

I could kiss you man!

Glad it helped, but I’ll pass on the expression of gratitude.

Not all my answers are useful,  but at least I get a few right every now and then.

Have Fun,

LyleHaze

9

:wink:

Hehe well the wiring was definitely okay…

with the pin out i had in mind that is!   :P

I should of just went back to the beginning and retraced every step!

(or just got it right the first time!)

I think i should stay true to my nationality and midibox on alcohol, it will yield better results!  :wink:

10

Well i finally connected up the LCD again with a fresh cable, this time in 8-bit mode,

and i got the 1st Line across the screen which TK mentioned in his post:

I disconnected D0-D3 to provide 4-bit mode, and voila, that heavenly “READY” status:  :smiley:

Its alivvvvvvve! Im so chuffed even to get this far, thanks again for all your help dudes!  :slight_smile:

Now to solder them midi sockets, and the Sid module.

11

hey smithy its good to see you got it sorted.

the guys here are top blokes and will do what they can to help if they can, and the feeling of finally getting it working is really great also!

had the same thing with my mtc display the other day, after all day checking and re checking my wiring turned out the schematic was wrong and it had to go to a different port!! much gusto to nils and smashtv for thier help.

this place and its members are great!

12

Group huuuug! :smiley:

13

hey smithy its good to see you got it sorted.

the guys here are top blokes and will do what they can to help if they can, and the feeling of finally getting it working is really great also!

had the same thing with my mtc display the other day, after all day checking and re checking my wiring turned out the schematic was wrong and it had to go to a different port!! much gusto to nils and smashtv for thier help.

this place and its members are great!

Thanks man. And i totally agree. This is the greatest community based site i have ever seen online.

There’s so many helpful, hardworking and trustworthy people on here,

its amazing how you can send money to people on here, whom you’ve never seen before in your life,

and always expect the goods to arrive.

Its quite a rare thing on the internet, obviously im not implying you can trust a newbie selling goods with their first post! But yeah, this is one awesome place to spend hours of time on!