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61  Using Arduino / Displays / Re: Using the LCM1602, What is the REAL Code for the Adruino Leonardo? on: March 20, 2014, 03:03:43 pm
You obviouly don't know about the Costructor statement that TELLS you how to connect it or how to use I2C.
I was under the impression that the constructor tells the library how the designer of the pc board chose to connect the IC pins to the interface pins.  It also tells the library what the I2C address for this particular setup is.

FYI it's obviously not 'obviouly' and it's constructor not 'costructor'.

62  Using Arduino / Displays / Re: Using the LCM1602, What is the REAL Code for the Adruino Leonardo? on: March 20, 2014, 12:13:02 pm
All I want is a simple pre written code that works so I can do more than just sit here and play at data entry puncher of code that may or may not and usually doesn't work!
I think there's a pre-written program that will 'play at data entry' for you, the I2C LCD Guesser.

It looks like you are using I2C adapters with your displays and there is no real standard for those.  

You have to determine the 'address' of the adapter which depends partially upon the particular chip on the adapter and partially upon the status of the jumpers which I think are right below the blue potentiometer.

You also have to determine the wiring between the chip on the adapter and the pins that go to the display.

If I am not mistaken the I2C LCD Guesser will do both of these for you.  The author will probably chime in here shortly to give you the correct answers if I am mistaken.


I2CLCDGUESSER -->;topic=157817.0;attach=67523
63  Using Arduino / Displays / Re: 20X4 2004A lcd does not respond. on: March 20, 2014, 12:03:35 pm
Could it be the same as this one? Just a broken lcd?
That is most probably correct.

64  Using Arduino / Displays / Re: Arduino LCD screen on: March 20, 2014, 11:04:27 am
What am I doing wrong?
Start a new thread.

Post a photograph that shows the 'random' pixels.

65  Using Arduino / Displays / Re: LCD display burns on: March 19, 2014, 05:00:15 pm
I don't see how you could come up with that display as a result of improper initialization or improper commands due to wiring or program errors.  I don't see how 'shifts' would cause that display either.

I think you could achieve that display by sending the specific data to the LCD to print eight spaces (0x00) followed by eight blocks (0xFF) to each row (or successively to all of the memory locations) but that most likely didn't happen here.

Since the problem arose after a working display was physically moved I still think it is a contact problem between the pc board and the display itself.


66  Using Arduino / Displays / Re: LCD display burns on: March 18, 2014, 05:38:59 pm
That might have done damage to a memory component, destroying half of the available characters (still guessing here, i'd expect lines to be gone, not 2 x half lines).
A 16x2 has two ICs or two epoxy blobs on the back one of which is the HD44780U or equivalent controller.  It contains all of the memory and enough I/O circuitry to drive the left half of this display.

The second IC or blob is the HD44100 or equivalent auxiliary controller which has the I/O circuitry to deal with the right half of this display.  Displays with more characters have additional auxiliary controllers.  All the details can be found by following the LCD Addressing link at

It looks like the connections between the main controller and the glass are defective.  I'm cheap so I would tinker with the bezel tension before getting out the hammer.  Maybe just remove those screws....


67  Using Arduino / Displays / Re: OPTREX DMC40457 don't work on: March 18, 2014, 01:22:01 pm

I know for a fact that this library is properly written, following all of the Hitachi recommendations.  When John was developing the program he plugged his display directly into the socket on the end of his Mega so there were no wiring issues.

On the other hand you are using a ribbon cable and then jumpers to get to the pins on your breadboarded processor so there are several possibilities that come to mind.

You will have to first verify that your processor itself is wired properly.  I see one capacitor near your crystal but most crystals require two.  There should be a decoupling capacitor between each power pin and GND as well.  These should be as close to the IC as you can get them.

You will also have to verify that your data and control lines for the LCD go to the pins that you have specified in your constructor.  Normally we can help with this if we have a good photograph, but the ribbon cable makes it difficult.

Some of my Optrex LCDs require a negative voltage for the contrast pin but the data sheet seems to verify that yours will work with a small positive voltage on pin 3 as long as you are running the LCD with 5 volts on pin 2.

68  Using Arduino / Displays / Re: 16 X 2 LCD with PCF 8574 (without using I2C library) on: March 18, 2014, 09:59:10 am
Your code is difficult to read because you have used 'quote' tags instead of 'code' tags, so please go back an edit your post to fix this.

I have not thoroughly gone through your code but a few things stand out.

Are you sure that your are using a PCF8574 and not a PCF8574A which has a different address?

How do you know that your contrast is 'moderate'?  If you are not sure of the setting then an extreme setting (0 volts) on pin 3 a good option.

It would be a good idea to use the 'initialization by instruction' sequence recommended in the HD44780 datasheet rather than the incorrect one used in a lot of the examples floating around the internet.  Follow the LCD Addressing link at for more information.  You will also find programming examples there.

Instead of using "{ if(x)//wanted to run this only once  ..." why don't you just put the relevant code in setup(), that's what setup() is for?

The LCD initialization sequence should certainly be in setup().  This change alone may fix your program and should be done first.

This (command=0xC0;//cursor at line 1 and position 1) is putting the cursor at line 1 and position 0 if you count from 0 - 9 and it is putting the cursor at line 2 and position 1 if you count from 1 - 10.   This isn't your basic problem since this address (0x40) is visible on all displays that I know of.

That should keep you out of trouble for a while.

69  Using Arduino / Displays / Re: Connect Arduino UNO to 3 Digit, 7 Segment, 12 Pins Display on: March 16, 2014, 02:24:37 pm
So this is your explanation for why I was able to find the pinout for the OPs display using Google after you tried and couldn't ?
Not at all.

What makes you think that I was unable to find the pinout for his specific display?
What makes you think that I even tried to do so (which I didn't).
Where did I say that there was something that I couldn't find?

In the second part of reply #8 I did explain, in general terms, how I go about finding pinouts for generic devices such as 7-segment displays.

When he said that it didn't work for him I responded (in reply #16) with some more specific instructions.

70  Using Arduino / Displays / Re: Connect Arduino UNO to 3 Digit, 7 Segment, 12 Pins Display on: March 16, 2014, 03:19:53 am
Let's try the Google explanation again with some more details.

The technique varies as Google changes it's interface along with the phase of the moon, and it may be different in other countries, but right now, in the US, here is how to proceed.

(1) Search for the term 3 digit 7 segment display with 12 pins.

(2) When the results come back don't look at any of them yet.  Instead, first limit the search to images.   There are several initial 'Search tools' that appear under the search window and 'Images' is one of them.   That does a pretty good job of sorting things out.

(3) When looking for data sheets a good way to get rid of some more of the junk is to limit the color to 'Black and White'.  If 'Color' is not one of the current search tools then click the 'Search Tools' button and 'Color' should appear as one of the new tools.  When you click 'color' then 'Black and White' should appear as an option.

I get slightly different results each time I do this.  Somehow I'm now getting some 4 digit displays first.

71  Using Arduino / Displays / Re: Connect Arduino UNO to 3 Digit, 7 Segment, 12 Pins Display on: March 15, 2014, 10:46:33 pm
Now I see the problem... his user name begins with a lowercase 'i'. 

72  Using Arduino / Displays / Re: Connect Arduino UNO to 3 Digit, 7 Segment, 12 Pins Display on: March 15, 2014, 10:37:33 pm
Okay. Thanks.
I've searched for 3 digit 7 segment display with 12 pins, but I found nothing about that. I've also searched on google pictures and the websites linked to the pictures.
Maybe it doesn't work for ghosts in nowhere land**.  

What search engine in what country were you using?

I have attached the first result that I got.  It happens to be common-cathode but the pinout is the same for common-anode.


** Try answering more of the questions in your profile!

73  Using Arduino / Displays / Re: Connect Arduino UNO to 3 Digit, 7 Segment, 12 Pins Display on: March 15, 2014, 10:31:41 pm
7-segment three digit  
 3 digit 7 segment
in a search engine ?
I tried it with Google and although the results were not exactly the same I still got pages and pages of results.

I also tried searching for 3 digit 7 segment display with 12 pins and again got pages and pages of results.

74  Using Arduino / Displays / Re: Connect Arduino UNO to 3 Digit, 7 Segment, 12 Pins Display on: March 15, 2014, 08:19:49 pm
Now it is time to refine your solution to use standard terminology.

These devices are designed to plug into IC sockets and possibly for that reason the pins are numbered in the same way that ICs are numbered, counterclockwise looking down from the top.

Therefore the first four lines of your solution look like this and the others follow suit.

Digital Pin 2: Display pin 2 (top) 11 A
Digital Pin 3: Display pin 6 (top) 7 B
Digital Pin 4: Display pin 4 (bottom) 4 C
Digital Pin 5: Display pin 2 (bottom) 2 D

I have searched for hours, before and found no answer.
It helps when you know what term to search for and a few Google tricks (if you are using Google).
The device is a 7-segment three digit LED. 

So if you do a search for 7-segment three digit then limit your search to images and further limit it to black and white you will see lots of pinout diagrams pop right up!

75  Using Arduino / Displays / Re: New DOGM204 Not working on Arduino on: March 14, 2014, 07:43:57 pm
Why are you messing around with the library ? Can't you do whatever you want to do without changing the library code ?
Not really since you can't fix delays between the steps in the initialization.  I don't think you can put delays between the writing of individual characters in a string either.

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