Problems connecting I2C devices
Problems that arise when the I2C peripheral board is powered by 5 volts and the MCU to which it is connected is powered by 3.3 volts.
Things become problematic if we have to connect a peripheral device powered by 5V, such as an LCD
display, compatible HD44780, with a MCU powered by 3.3V and not 5V tolerant, such as an ESP. If the I2C
LCD board has two pull-up resistors mounted on the 5V, they must be removed and two external resistors
connected to the 3.3V of the ESP mounted. It is true that the presence of the pull-up resistor limits the
current on the ESP input, but the chip could be damaged after some time.
display, compatible HD44780, with a MCU powered by 3.3V and not 5V tolerant, such as an ESP. If the I2C
LCD board has two pull-up resistors mounted on the 5V, they must be removed and two external resistors
connected to the 3.3V of the ESP mounted. It is true that the presence of the pull-up resistor limits the
current on the ESP input, but the chip could be damaged after some time.
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