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Connecting 5V LCD and 3.3V OLED to Same I2C Pins on NodeMCU ESP8266

Travisek 804 3
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  • #1 19193037
    Travisek
    Level 5  
    Hi, I have a nodemcu v3 esp8266.

    The 2x16 LCD display is powered by VCC = 5 V, while the 0.96'' OLED is powered by 3.3 V.

    I have an I2C converter attached to the LCD display, the OLED also uses I2C.

    Knowing that the LCD is connected under 5 V and the OLED under 3.3 V - can I connect both displays under the same SCL and SDA pins to the ESP (D1 and D2) ?

    Thanks
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  • #2 19193136
    lucass17
    Level 14  
    There will probably be no communication with the 5V LCD, because in the datasheet note in the first better LCD the logical one starts at 3.5V. You need to use a converter or circuit that will match the logic levels.
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  • #3 19193353
    khoam
    Level 42  
    Travisek wrote:
    For the LCD display I have an I2C converter attached , the OLED also uses I2C.
    Knowing that the LCD is connected under 5 V and the OLED under 3.3 V - can I connect both displays under the same SCL and SDA pins to the ESP (D1 and D2)?
    .
    As long as there will be 3V3 logic states on the I2C lines on the NodeMCU side and there is already a 5V/3V3 logic level converter on the LCD side, then you can.
  • #4 19253495
    504651921
    Level 15  
    I managed to run the LCD without a converter - the only problem was getting the bias correct - but I got around that a bit by running the LCD in single line mode (different refresh rate) and everything is readable.
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