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I have bought some I2C adapters like this one.
http://www.ebay.com/itm/281234403721?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Is it possible to use this with an 20x4 display?
I have found similar I2C adapters on the net that is suppose to do 20x4 disaplay.
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It gets hot so it must be working
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http://forum.arduino.cc/index.php?topic=214511.0
this an ongoing thread about that backpack.
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Quote
...Is it possible to use this with an 20x4 display?
Yes.   All of the character mode displays using the HD44780U or equivalent controller chip will work with the I2C adapters such as yours.

Don
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Wow. You can't beat the price ($1.38). It costs more for a cup of coffee at the local coffee shop.
Yeah , I think that it will work with a 20x4 display since the parallel connections for both types of
displays are the same. You have a display with "n" connections and a black box with "m" connections
and the software sends what it needs for the type of display you want to control.
If you don't have the configuration info you can find out using a program called a "GUESSER"
that tries different configurations until it gets a match and then prints the configuration to
the serial port where you can see it using the serial monitor. You have to change the serial monitor
Line Ending to "Newline" for it to work. Read the instructions in the code and when you get the
config info paste it into an lcd example sketch from the library.
http://forum.arduino.cc//index.php?topic=157817.msg1235230#msg1235230  
You'll need the library from here to use the guesser.
https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads
If you don't know how to change libraries then ASK.
when you try the guesser , if you have a 4-bit parallel display available PLUG IT INTO THE ADAPTOR because when
the GUESSER finds a match it will BLINK THE BACKLIGHT 3 TIMES and then DISPLAY the CONFIGURATION
(ie: "lcd(0x27,  2,  1,  0,  4  ,5,  6,  7 , 3,  POSITIVE)"
« Last Edit: January 31, 2014, 08:30:23 pm by raschemmel » Logged

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Yes it is possible, You will need to install F Malpartida's Liquid Crystal library instead of the one that is included in the IDE.
The Library can be found here: https://bitbucket.org/fmalpartida/new-liquidcrystal/wiki/Home
It is a very fast and very versatile display library that completely replaces the original LiquidCrystal lib found in the IDE folder...
Just follow the included install instructions.
It is a really good idea to search for IIC LCD in the forum and read all you find. There are several threads and each was helpful to me in one form or another... My display code worked W/O modification the first time I used it. It was based on the Forum examples and the enclosed sketch from yourduino.comhttp://arduino-info.wikispaces.com/LCD-Blue-I2C
I've enclosed a sample sketch from Yourduino.com that worked for me... there are perhaps 4 different IIC adapters and the difference is the way the PCF8574 IIC interface IC is wired to the LCD There is information on the yourduino site to deal with the different wiring found on the IIC backpacks. MY adapter is the GY-IICLCD plugged into a 4 X 20 line display, It works extremely well with the F Malpartida Library. Much faster than the LiquidCrystal library supplied with the IDE.

Doc

* IICLCD.ino (2.17 KB - downloaded 8 times.)
« Last Edit: January 31, 2014, 08:30:11 pm by Docedison » Logged

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better too much information than too little eh ?
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Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,
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