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[SOLVED] Cabling LCD 4*16 with PIC18F4550

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dido1987

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hello;
i want to connect my 4*16 LCD with my PIC
on ISIS LCD has 14 pin but in real it has 16 pin so i wanna know the pin 15 and 16 to what i connect them and am using only the pin D4, D5, D6, D7 for data so the other pin D0, D1, D2, D3 i should let them NOT CONNECTED or i connect them to GROUND
thanks in advance
 

ckshivaram

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15 and 16 are again vcc and ground respectively.. they are used for backlight purpose in real time lcd.. your circuit will work with or without it....

ground other D0 to D3 so that it does not cause stray effects... its good practice to pull unused pins to ground...

---------- Post added at 15:39 ---------- Previous post was at 15:38 ----------

D0 to D3 of LCd should be grounded...
 

dayanpad

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I think you will be helpful this

circuit+diagram+to+interface+LCD+with+Microcontroller+8051.jpg
 

JayantD

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what does this circuit tell the original poster about???? its not related to what he has asked.......

The schematic further clarifies how a LCD module is to be interfaced to a microcontroller. As to grounding of unused D0..D3, I think they have internal pullups and can be left floating safely, without causing issues. Will do a double-check and confirm, though!
..Edit..
The HD44780 datasheet mentions that D0..D3 are disabled for 4 bit data transfers. These pins are shown unconnected in the block diagrams.
 
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ckshivaram

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The schematic further clarifies how a LCD module is to be interfaced to a microcontroller. As to grounding of unused D0..D3, I think they have internal pullups and can be left floating safely, without causing issues. Will do a double-check and confirm, though!

the original poster is asking about LCD unused pins... and what are you talking about??? whats the use of grounding the port pins physically?? read the requirement properly or comment properly which part you are answering without confusing others.....
 

JayantD

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I'm talking about D0..D3 pins of the LCD, and NOT about the microcontroller ports. Apologies if my reply confused you..
 

ckshivaram

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As to grounding of unused D0..D3, I think they have internal pullups and can be left floating safely, without causing issues.

LCD does not have pull up.... please take care before you answer.. and answer only if you have confirmed information...........
 

JayantD

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ckshivram,

Agreed, LCD doesn't have pullups.. We're talking about "4x16 LCD module" which has a hitachi HD44780 or equivalent controller on board. This chip generates all the timing etc required to drive the LCD. The user's microcontroller program writes into the RAM of the HD44780 using D0..D7, E, RW, RS signals.. This has been clearly shown in the schematic posted by dayanpad above..

I fail to understand why you're taking an aggressive stand on this, some politeness would be helpful.
Regards,
JayantD
 

dido1987

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am confused right now because am gonna make my card and am not sure how to connect my LCD 8O
 

sudeepr

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if we see the original poster question, and what what dayanpad has posted has no connection.. the question is about pin 15 and 16 and using or leaving the data pins in 4 bit mode... and his reply does not convey anything about it.. and jayantd,, i too feel you should read words carefully of the original poster and not the earlier posts...

DIDO1987...
you can ground the unused data pins of LCD....
 

ckshivaram

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jayantD the arrow mark you have shown in the data sheet is for external pull up resistor used or not.

I have tested that already and data sheet is correct.. he does not talk of internal pull up of LCD.. dont confuse yourself..
 

dido1987

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OK I will connect my unused pin to ground and I will test it
 

bjuric

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Check pins 15 & 16. Last LCD I used (DEM20486 i think) had pins 15 & 16 reversed. I got pissed thinking it was broken :)
And use resistor for backlight LED. Most displays don't have onboard resistor.
 

bjuric

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Do you really read the post...read the first post and understand the posters requirement...

he says on ISIS he has lcd with 14 pins

Maybe You should read it.
"on ISIS LCD has 14 pin but in real it has 16 pin so i wanna know the pin 15 and 16 to what i connect them "

On the other hand the question is a bit ambiguous. The OP didn't specify if he's going from ISIS to real LCD, or the other way around.
 

dido1987

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hi every body,
i didn't connect the 15 and 16 pin to any thing and my LCD it works
and i asked an engineer in a electronic society and he tell me that in both case it works if i connect the D0,D1,D3,D4 to ground or no
any way thanks everybody:-D
 

ckshivaram

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as my previous post 15 and 16 are used for backlight, connecting it or not would not have any effect on the working and nor leaving or gounding the pins would effect in normal condition but would effect in noisy environment...
 

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