# ESP32 Starter kit and I2C voltage levels

**URL:** <https://forum.sunfounder.com/t/esp32-starter-kit-and-i2c-voltage-levels/3902>\
**Category:** Learning kit for Arduino\
**Created:** [October 15, 2025, 10:35pm UTC](https://forum.sunfounder.com/t/esp32-starter-kit-and-i2c-voltage-levels/3902 "2025-10-15T22:35:39Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Grphon3rd](https://avatars.discourse-cdn.com/v4/letter/g/3da27b/32.png) [@Grphon3rd](https://forum.sunfounder.com/u/Grphon3rd)\
**Post date:** [October 15, 2025, 10:35pm UTC](https://forum.sunfounder.com/t/esp32-starter-kit-and-i2c-voltage-levels/3902/1 "2025-10-15T22:35:39Z")

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Please forgive a newbie question… I purchased the ESP32 starter kit and am having fun. I am a little concerned about the include LED display however. It requires 5V on the VCC pin, but the ESP32 is not 5V tolerant. does the I2C board reduce the voltage on the CLK and SDA pins to 3.3V to keep the arduino happy? I could not find any documentation one way or the other.

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**Author:** ![SunFounder\_Moderator](https://avatars.discourse-cdn.com/v4/letter/s/34f0e0/32.png) [@SunFounder\_Moderator](https://forum.sunfounder.com/u/SunFounder_Moderator)\
**Post date:** [October 16, 2025, 6:20am UTC](https://forum.sunfounder.com/t/esp32-starter-kit-and-i2c-voltage-levels/3902/2 "2025-10-16T06:20:39Z")

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The VCC pin must be connected to 5V: The backlight and driver circuit of the LCD display require a 5V power supply. Connecting it to 3.3V will result in low screen brightness or no display.

The GND pins must share a common ground: The GND of the ESP32 and the GND of the I2C board must be connected together. Otherwise, communication will fail due to inconsistent reference voltages.

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<div class="post-metadata">

**Author:** ![Grphon3rd](https://avatars.discourse-cdn.com/v4/letter/g/3da27b/32.png) [@Grphon3rd](https://forum.sunfounder.com/u/Grphon3rd)\
**Post date:** [October 16, 2025, 11:59am UTC](https://forum.sunfounder.com/t/esp32-starter-kit-and-i2c-voltage-levels/3902/3 "2025-10-16T11:59:14Z")

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My apologies for not asking the question clearly. I realize the VCC pin must be connected to 5V and the grounds are tied together correctly. My question is about the voltage on the CLK and SDA pins. Does the LCD display put 5V or 3.3V on these pins? Also should the pull-up resistor on these pins be tied to 5V or 3.3V ??

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<div class="post-metadata">

**Author:** ![SunFounder\_Moderator](https://avatars.discourse-cdn.com/v4/letter/s/34f0e0/32.png) [@SunFounder\_Moderator](https://forum.sunfounder.com/u/SunFounder_Moderator)\
**Post date:** [October 17, 2025, 6:48am UTC](https://forum.sunfounder.com/t/esp32-starter-kit-and-i2c-voltage-levels/3902/4 "2025-10-17T06:48:23Z")

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The voltage on the SCL/SDA pins of the LCD1602 module is determined by the module’s operating voltage:

If the module is connected to 5V, the pins output 5V.

If the module is connected to 3.3V, the pins output 3.3V.

The pull-up resistors must match the voltage level of the ESP32 pins. It is recommended to connect them to 3.3V.