Protect ESP32 from Overvoltage via External UART Connection

[leansolution]

I have a TJC HMI display similar to Nextion. It communicates with the ESP32 through UART. The display operates at 5V, but the specification table indicates that the Tx and RX pin voltages are 3.3V, which is acceptable for the ESP32.

Before connecting the display to the ESP32, I checked the voltage using a digital multimeter (DMM). The yellow wire corresponds to the RX pin, which is currently showing a 3.28 voltage reading. Which seems to be Okay

But when I connect the Tx pin of TJC with DMM, it shows 4.58V, which is alarming for ESP32

Am I testing the right way, or am I doing it wrong? Your suggestions matter. I want to protect my ESP32

[jim-p]

See this topic for the answer. Why are you asking the same question again?

ESD Protection for UART and I2C

I am designing a PCB board that features the ESP32 as the microcontroller. The UART pins will connect to an external HMI LCD, specifically the TJC (a Chinese version of Nextion), through a screw terminal. Additionally, I have included a screw terminal for connecting external I2C sensors. [image] ESD events can occur when someone touches the screw terminal, potentially damaging my MCU. One way in my Mind is to use TVS Diodes [image] However, I am worried that adding resistors might slow do…

[sonofcy]

If in doubt, use a level shifter, assuming the ESP32 isn't already damaged.