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  1. #1
    Join Date
    Oct 2012
    Posts
    9

    Default Interfacing with Arduino I2C LCD

    I bought one of these Arduino I2C 20x4 LCD modules.

    I got the LCD module in today. It has a slightly different back board, but that's not a bad thing. They extended the A0, A1 & A2 slave address pins out to solder/short PCB pads. This will affect the advertised address from 7 bit address of 0x27 (A0:A2 all "1"s) to a 7 bit address of 0x20 (A0:A2 all "0"s). Shorting the jumper pads ties the pin(s) to +5V. At least the modules slave addresses can be easy to change and set... that's a good thing! I was expecting to get stuck with a fixed slave address.

    Again, the web site is wrong about the advertised module address - it is 0x20 as shipped, not 0x27, at least for the module they sent me.

    Past that, it's using a basic I2C bi-directional I/O expander IC - PCF8574T.

    Addressing the module is pretty strait forward, though the data byte being sent needs to be constructed as follows:

    LCD runs in 4 bit mode - DB4 : DB7 are data bits - DB0 : DB3 are not connected at all.

    Data Byte sent via I2C:

    bit7 = B/L LED (0=on; 1=off)
    bit6 = RS (Register Select)
    bit5 = R/W (Read/Write)
    bit4 = E (Enable)
    bit3 = DB7 data
    bit2 = DB6 data
    bit1 = DB5 data
    bit0 = DB4 data

    All the normal commands are available under HD44780 datasheet, including 2-way communication with module.

    BTW, the soldering was very good when I got it. Due to my test probe use to confirm the hookup, it looks worse then when I got it.
    Attached Images Attached Images    
    Last edited by norohs; - 27th October 2012 at 19:03.

  2. #2
    Join Date
    Nov 2003
    Location
    Wellton, U.S.A.
    Posts
    5,926

    Default Re: Interfacing with Arduino I2C LCD

    Do you want to share your PBP code? Or is this just an advertisement?
    Dave
    Always wear safety glasses while programming.

  3. #3
    Join Date
    Oct 2012
    Posts
    9

    Default Re: Interfacing with Arduino I2C LCD

    Wow, really?

    Seems what I've shared is at least relevant considering this question has been asked before... in light of the answers offered.

    This is the documentation section, right?

    My code is embarrassing. I'm sure anyone can read what I've posted and come up with much better code then I did. Frankly I'm not up for the criticism about how I wrote it... seeing your comments, I'm glad I didn't post it.

  4. #4
    Join Date
    Oct 2009
    Location
    Utah, USA
    Posts
    442

    Default Re: Interfacing with Arduino I2C LCD

    Frankly I'm not up for the criticism about how I wrote it... seeing your comments, I'm glad I didn't post it.
    Norohs,
    so what was the point of your post?? Seems reasonable to me to want to see your code.

    I've been around here a while and have not ever noticed "criticism" regarding someone elses code. Constructive help, yes. Suggestion on how to improve, yes.

    If someone posts here with a real intent to learn and ask for help... they always get it.

    You, on your third post, have managed to be rude and condecending to someone here who has over 5 thousand posts to their credit.
    No the sheer number of posts does not grant someone special status. But why would you assume someone is going to criticize your code??

    Strange way to start a life in a fourm
    Dwight
    These PIC's are like intricate puzzles just waiting for one to discover their secrets and MASTER their capabilities.

  5. #5
    Join Date
    Dec 2005
    Posts
    1,073

    Default Re: Interfacing with Arduino I2C LCD

    Quote Originally Posted by Heckler View Post
    You, on your third post, have managed to be rude and condecending to someone here who has over 5 thousand posts to their credit.
    None of which have been critical or condescending.

  6. #6
    Join Date
    May 2007
    Posts
    604

    Default Re: Interfacing with Arduino I2C LCD

    Quote Originally Posted by dhouston View Post
    None of which have been critical or condescending.
    Agreed +1.
    Why pay for overpriced toys when you can have
    professional grade tools for FREE!!!

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