The CHIP_PU (Chip PowerUp) pin on ESP32 family processors such as the ESP32S2 is equivalent to the EN (enable) or ~RST pin on other microcontrollers.
When CHIP_PU is pulled high (i.e. to 3.3V), the ESP32 is enabled and will run the firmware.
When CHIP_PU is pulled low (i.e. to GND), the ESP32 is disabled and shut down and will not run the firmware.
In other words, in most applications you want to connect a 10kOhm resistor from CHIP_PU to 3.3V and – if needed – a reset button from the CHIP_PU pin to GND. You can not operate the ESP32S2 without a pullup resistor . This is clearly stated in the ESP32S2 datasheet, section 2.2:
Note: Do not leave the CHIP_PU pin floating.
On the ESP32S2-WROOM-I module, the CHIP_PU is directly connected to the module’s EN pin wut