uPesy ESP32 Wrover DevKit

Simplified version

This version, adapted for beginners, presents the main features of the pins.

Full version

For more details on the ESP32 pins, I encourage you to read the ESP32 pinout guide .

Pin tolerance

• The ESP32 is a microcontroller that operates at 3.3V. The logic levels are therefore 0 and 3.3V and not 0 and 5V. That is to say that the output voltage of the GPIO pins is 3.3V, and the input voltage must not exceed 3.3V. The GPIO pins are not designed to have logic levels of 5V.

  Note

  Most modules/sensors can work with 3.3V logic levels, but if this is not the case, you will need level shifters (or possibly voltage divider bridges) to switch from 3.3V to 5V and vice versa.

  Warning

  Since the ESP32 was not designed to receive 5V on these GPIO pins, you can damage the ESP32 pins if they are exposed to this voltage for too long.

• The voltage measured by the ADC must not exceed 3.3V (and not negative, of course).

Powering the uPesy board

There are several ways to power the uPesy ESP32 board Wrover DevKit:

• The easiest way is by USB in 5V, connecting the board to a computer or an external battery (power bank). We can then use the pins 5V and 3V3 of the board to supply an electronic circuit in 5V and 3.3V, respectively. The regulator of the board generates the 3.3V voltage.

• You can also power the board directly on the \(V_{IN}\) pin via an external power supply. You must remember to connect the power supply’s ground to the board’s GND pin. There is no 5V voltage on the 5V pin, and only a 3.3V voltage is available on pin 3V3. Indeed, the 5V voltage comes only from the USB; the board does not have a 5V regulator.

  Warning

  The input voltage on pin \(V_{IN}\) must be between 3.6 and 7V maximum. A voltage around 5V is optimal.

• You can also use the first two methods simultaneously: having an external power supply connected to the \(V_{IN}\) pin while having the board connected to the computer (the two grounds must be attached). This is quite convenient for communicating with the serial monitor of the Arduino IDE while having the ESP32 powered by another external electronic circuit. It functions like so :

  • If \(V_{IN}\) < \(V_{USB}\) , with \(V_{USB}\) =5V, then it is the USB that will be mainly used to power the ESP32.

  • If \(V_{IN}\) > \(V_{USB}\) , then it is the external power supply that will be mainly used to power the ESP32.

  Warning

  You must also be careful with this power supply mode to avoid irreversible damage to the ESP32 board and/or the computer’s USB port and/or the external power supply in case of an error. This operation is usually safe on the uPesy board thanks to a protection circuit that prevents back current in the power supplies. Unfortunately, this is not the case for all ESP32 boards.

Built-in protections

The uPesy ESP32 Wrover Devkit board has a set of protections to avoid damaging it. These protections are insufficient to prevent all possible handling errors: the board is therefore not indestructible.

The board includes the following protections :

• Electrostatic discharge protection on the USB port

• Short circuit protection on the \(V_{IN}\) , 5V and 3.3V rails: Self-resetting thermal fuses of 350 mA are used on the \(V_{IN}\) and 5V rails. It is important to avoid drawing too much current on the board; otherwise, they may trip. They are automatically activated and deactivated (polyfuse).

• Protections against current injections on pins 5V and 3V3 to avoid inadvertently injecting a current on these power supply pins.

• Overvoltage protection on \(V_{IN}\) pin: a passive circuit limits the \(V_{IN}\) voltage; however, the excess will be dissipated as heat and eventually trigger the self-resetting thermal fuse.

• Protection against polarity inversion between \(V_{IN}\) and GND.