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Thread: Teensy Audio and I2C serial converter for LCD screen

  1. #1

    Teensy Audio and I2C serial converter for LCD screen


    I would like to get a Teensy Audio Board working together with LCD screen running over I2C with a Serial Converter board (

    The LCD screen needs 5v so is there anything specific I need to do to get this working properly?

    I have both 5v and 3.3v on my breadboard.

    At the moment I am trying to run the Teensy3.0/3.1/LC I2C Scanner sketch but I am not getting any results on the serial monitor.

    I have 4.7k pullup resistors on the SDA and SCL to 3.3v and 5v going to the screen.

    I have tried the lcd without the teensy audio board and am getting the same problem... so I think I am asking about 2 separate issues - 1. getting the i2c to work, and 2. getting it to work with the audio board.

    Thanks for any advice or help!


  2. #2
    Sorry, I realized I wasn't pulling pin 11 to ground, so it is now running the scanner test correctly and it shows ACK on Addr 0x27

    I'm not having any luck getting the LCD to work though, any advice much appreciated

    <added> what is happening now is that when I try to upload this hello world sketch:

    #include <Wire.h> 
    #include <LiquidCrystal_I2C.h>
    LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x20 for a 16 chars and 2 line display
    void setup()
      lcd.init();                      // initialize the lcd 
      // Print a message to the LCD.
      lcd.print("Hello, world!");
    void loop()
    The LCD screen just goes black. No backlights or anything. When I run the I2C scanner I get the blue backlight and the white cursors OK.

    As mentioned in my first post, I have the Serial Converter VCC going to 5v and the 4.7k pullup resitors going to 3.3V but I'm not sure if tat is right. I have removed the audio board from the setup and still get the same problem.

    I'm also not sure if I will be able to use the 5V LCD screen on the same I2C pins as the audio board when I get the LCD screen to work.
    Last edited by Robhilken; 04-26-2016 at 08:17 AM.

  3. #3
    It seems it was just a matter of finding the right library. This one worked -

  4. #4
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Glad to see you found a working lib.

    These cheap Chinese products with so little info can be a real challenge. Without a schematic or even the part number of the chip they used, guesswork is needed....

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