4 Channel Bi-directional Level Translator

Each channel uses a BSS138 MOSFET with pull-up resistors on both sides, translating signals in both directions between a low-voltage side (LV, e.g. 3.3 V) and a high-voltage side (HV, e.g. 5 V). Because it is bidirectional, it works on open-drain buses such as I2C as well as UART and slower SPI and GPIO lines, with no direction pin to manage. Power the LV and HV pins from the two system rails, tie the grounds together and route each signal through one channel. It is the usual way to connect 3.3 V boards such as the ESP32 or Raspberry Pi to 5 V sensors, displays and Arduino boards.