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Topic: Can't get LCD 1602 I2C show any characters (Read 3121 times) previous topic - next topic

rpt007

#60
Jan 19, 2016, 12:52 pm Last Edit: Jan 19, 2016, 04:54 pm by rpt007
Hi all,

just a short update of my findings:

Today I received another blue LCD display; this time I bought a Sainsmart 1602 incl. an I2C adapter mounted already on the backside.
My tests (IDE 1.6.7 & NewLiquidCrystal 1.3.4 library) showed the following results:

- Sainsmart I2C adapter comes with the 0x27 address (at least in my case)
- it works out of the box without having to add the "backlight();" command after each lcd.print command
- the I2C adapter is operating with a Philips PCF8574T chip
- ID of this Philips chip is: "ID knM00503"

- alternative I2C adapter with same blue 1602 LCD display comes with 0x3F address
- there is no manufacturer listed on the PCB; the only identification is A0 A1 A2 (LCD version 1, see this.)
- in this case I needed to insert my workaround command "backlight();" after each lcd.print .. line
- the adapter is also driven by a Philips PCF8574AT chip
- ID of this Philips chip is: "ID knM96183"

Maybe this helps those who have a similar problem displaying text on the LCDs.

Raimund

Before you ask:
Did you really read and understand "How to use this forum"  -> http://forum.arduino.cc/index.php?topic=148996.0
AND:
Do you have already some solution or is a part of the problem sitting in front of the screen?  :)

david_prentice

#61
Jan 19, 2016, 02:22 pm Last Edit: Jan 19, 2016, 02:28 pm by david_prentice
The part number of the 0x3F chip will be PCF8574.  i.e.0x38-0x3F
The part number of the 0x27 chip will be PCF8574A i.e. 0x20-0x27

This thread has got 60 messages.   Surely you download one library and run one "sniffer" sketch.
And your I2C display works 100%.

I make that one original question.
One reply with a link to the library and diagnostic sniffer.
One message from the OP to confirm that her problems are solved.

Occasionally there will be language difficulties.     Or an unusual technical error.    In which case you might get an extra explanation from the LCD expert(s).

David.

Hi all,

just a short update of my findings:

Today I received another blue LCD display; this time I bought a Sainsmart 1602 incl. an I2C adapter mounted already on the backside.
My tests (IDE 1.6.7 & NewLiquidCrystal 1.3.4 library) showed the following results:

- Sainsmart I2C adapter comes with the 0x27 address (at least in my case)
- it works out of the box without having to add the "backlight();" command after each lcd.print command
- the I2C adapter is operating with a Philips PCF8574AT chip
- ID of this Philips chip is: "ID knM00503"

- alternative I2C adapter with same blue 1602 LCD display comes with 0x3F address
- there is no manufacturer listed on the PCB; the only identification is A0 A1 A2 (LCD version 1, see this.)
- in this case I needed to insert my workaround command "backlight();" after each lcd.print .. line
- the adapter is also driven by a Philips PCF8574AT chip
- ID of this Philips chip is: "ID knM96183"

Maybe this helps those who have a similar problem displaying text on the LCDs.

Raimund


Thanks for the update.

From your report it appears that the "faulty" LCD module DID NOT come with the I2C controller installed.

Please verify because the OP never did answer / verified the header connections.

At least I have not seen  such verification posted.
"Thunder is good, thunder is impressive; but it is lightning that does all the work"
Mark Twain

I do not read nor respond to thunderous posts.

rpt007

#63
Jan 19, 2016, 05:15 pm Last Edit: Jan 19, 2016, 05:36 pm by rpt007
Hi,

I just edited my previous post as indeed there was an error: the Sainsmart chip is a PCF8574T (the other one is a PCF8574AT).
In fact the PCF8574T comes with address 0x27 and the PCF8574AT with 0x3F (default values if you don't change anything on the board.

To make it crystal clear, what chip is on what adapter, here some pictures:
(hope that works)




@Vaclav:

The "A0 A1 A2" module was a separate buy to add the I2C feature to my display.
Sainsmart display came with the module mounted.

Edit: sorry, can't get the pictures being displayed although my test of the URLs did and still does work.
So here are the links in quotes:
"http://www.directupload.net/file/d/4238/vamagvrg_jpg.htm"
"http://www.directupload.net/file/d/4238/qb4chqeq_jpg.htm"
Before you ask:
Did you really read and understand "How to use this forum"  -> http://forum.arduino.cc/index.php?topic=148996.0
AND:
Do you have already some solution or is a part of the problem sitting in front of the screen?  :)

#64
Jan 19, 2016, 07:18 pm Last Edit: Jan 19, 2016, 07:36 pm by Vaclav
Code: [Select]
The "A0 A1 A2" module was a separate buy to add the I2C feature to my display.
Sainsmart display came with the module mounted.


Half bingo!

That would explain possible cold solder joints IF the OP fellow did same.
We do not know that.

And the OP never did came up with clear picture showing the I2C header connections.
If I recall, he stated that  he cannot get in between the piggyback module and the LCD!


And it would also explain why backlight worked - separate SINGLE signal and ground from  controls and data.
Also the control and data pins FROM the I2C module to LCD  MAY be different that from the one which came assembled.

And we do not know that either.

I would assume the the SPI addresses are burned in the controller ( we  seen two different version of same base chip ) which indicate that the output pins may also be different.

So if wrong parameters ( I/O control and a data pins from the I2C controller )  are passed to the constructor - all bets are of.



 
"Thunder is good, thunder is impressive; but it is lightning that does all the work"
Mark Twain

I do not read nor respond to thunderous posts.

ELYA

Hello everyone

I solved the problem.
It is a silly :(  I have done extensive experiments with Libraries but it did not change the result.( I get a blue screen with square without text) the issue was  the soldering. I did not solder my module pins to the LCD.It seams that some pin was not touching the micro strip on the lcd board. But now it works as it should be.

So everybody: solder your module and make sure that all pins are well connected to the micro-strip :)

Hello everyone

I solved the problem.
It is a silly :(  I have done extensive experiments with Libraries but it did not change the result.( I get a blue screen with square without text) the issue was  the soldering. I did not solder my module pins to the LCD.It seams that some pin was not touching the micro strip on the lcd board. But now it works as it should be.

So everybody: solder your module and make sure that all pins are well connected to the micro-strip :)
Thanks for update.
Nothing silly about it. You have been asked several times to verify the actual connection between  the piggyback and the LCD. Especially if you did it yourself. 
I for one still would  love to see the detailed picture BETWEEN the piggyback and the module.
Just for reference.

Hope you will now appreciate the old saying "it works better if you  plug it in ".

Cheer up, there are worst things that can happen.

Again, thanks.
 


 
"Thunder is good, thunder is impressive; but it is lightning that does all the work"
Mark Twain

I do not read nor respond to thunderous posts.

ELYA

Hi Vaclav

>>You have been asked several times to verify the actual connection between  the piggyback and the LCD

Are you sure?? I don't see anyone asked me about this before.

Hi Vaclav

>>You have been asked several times to verify the actual connection between  the piggyback and the LCD

Are you sure?? I don't see anyone asked me about this before.
No, after so many participants in the discussion I am not sure whom did I ask.
I often ask about hardware , so I am sure it did came up.
Cheers 
"Thunder is good, thunder is impressive; but it is lightning that does all the work"
Mark Twain

I do not read nor respond to thunderous posts.

dwightthinker

I have a 1602 display mounted on one of those shields with the
push buttons ( not IIC ), On inspecting mine before powering it
on, I found a solder jump between pins 10 and 11.
This made me think about your pot shorting problem.
Pin 2 is VCC and pin 3 is Vo. Should these two pins be shorted,
either on the 1602 board or the IIC board, the turning of the pot
will do exactly as you are seeing.
Not adjustment and then shorting at one extreme.
Do some careful inspection of the solder at these two pins.
Dwight

AdamPo

Hello,

I have went through this thread because I had the same problem with characters not displaying. I used the code from @rpt007 with no luck.

The solution I found in the end was rather simple and I felt a bit dumb. I only had to turn
the potentiometer on the I2C module a little and the characters showed up.

Hope it helps some of you,

Adam

jang87

Hello,

I have went through this thread because I had the same problem with characters not displaying. I used the code from @rpt007 with no luck.

The solution I found in the end was rather simple and I felt a bit dumb. I only had to turn
the potentiometer on the I2C module a little and the characters showed up.

Hope it helps some of you,

Adam
Same here. Just needed to turn the potentiometer on the I2C. :D

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