uPesy ESP32 Wroom DevKit v2

Simplified version

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

Note

You can put the ESP32 on the paper sheet to better locate the pins. 😉

Full version

I strongly invite you to consult the page on the detailed operation of the ESP32 pins for more information.

Details on pin numbers

You will notice that the pins are numbered out of order, unlike the Arduinos boards. It will be necessary to refer to the pinout to know the pin number and not deduce it from the position of the pin.

There is a link between the Arduino keywords and the ESP32 pins. The connection is between the keywords and the pins of the ESP32, not between the Arduino and the pins of the ESP32. However, this association is incomplete and often a source of errors. It is therefore not recommended to use it, but it can be helpful to know it to adapt more easily a code initially written for an Arduino to an ESP32.

Here is the link when chosen as the type of board ESP32 Dev Module or DOIT ESP32 DEVKIT V1

ESP32 module

The brain of the board is the ESP32 module. It is a powerful microcontroller made by Espressif. On the uPesy board, a WROOM module is used: it contains an ESP32 chip and an elementary circuit to make it operate.

Here are links to the manufacturer’s datasheet:

• WROOM module https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32_datasheet_en.pdf

• Chip ESP32 https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf

USB/UART converter

This converter plays the role of “interpreter” between the computer and the ESP32 module so that they can communicate together. A CP2102 chip from Silicon Labs is used for this task. It is natively supported by Windows, macOS and Linux. There is, therefore, no need to install any particular driver.

Power management

This section of the board is responsible for power management. It contains, among other things, a 3.3V voltage regulator and protection. Its operation will be detailed in the Use section.

Connectivity

The USB-C connector of the board allows for communication with the computer. It will allow uploading a program to send messages.

The two buttons EN and BOOT of the board allow control of the state of the ESP32:

• EN: This button, also called RESET, is used to restart the ESP32 forcefully

• BOOT: Using this button alone is not very useful. It acts on the behavior of the ESP32 during the boot process.

These buttons can manually put the ESP32 in FLASH mode, which allows loading a new program on the ESP32. Usually, the ESP32 automatically goes into this mode when the upload is done via USB with the CP2102 converter.

When :

Connecting........_____....._____....._____....._____....._____....._____....._____....._____....._____....._____

Here is the combination to produce :

• Press and hold the EN and BOOT buttons simultaneously for 2 seconds

• Release the EN button while holding down BOOT for 2 seconds

• Release the BOOT button

Voltage tolerance of the pins

• The ESP32 is a microcontroller that works in 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 .

• The voltage measured by the analog to digital converter must not exceed 3.3V (and not harmful, of course).

Power supply for the uPesy board

When the board is powered, a red LED lights up. There are several ways to power the uPesy ESP32 Wroom DevKit board:

• The easiest way is by USB in 5V, connecting the board to a computer or an external battery (power bank). You can then use the 5V and 3.3V pins to power an electronic circuit.

  Note

  The voltage of the 5V pin comes only from the USB.

• You can also supply the board directly on the pin \(V_{IN}\) with an external power supply. It would help if you remembered to connect the power supply’s ground to the board’s GND pin. There is no 5V voltage on pin 5V, and only 3.3V is available on pin 3V3.

  Warning

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

• You can also use the first two methods at the same time. This means having an external power supply connected to the \(V_{IN}\) pin and the board connected to the computer (the two grounds must be attached) . This is very convenient to talk to the Arduino IDE serial monitor while having the ESP32 powered by another external electronic circuit. The operation is as follows:

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

  • If \(V_{IN}\) > \(V_{USB}\) if the ESP32 is not connected to the external power supply, then the external power supply will be used primarily to power the ESP32.

  Warning

  In case of error, it is also necessary to remain cautious in this power supply mode to avoid irreversible damage to the ESP32 board and/or the USB port of the computer and/or the external power supply. This operation is usually safe on the uPesy board thanks to a protection circuit that prevents reverse power supply currents. Unfortunately, this is not the case for all ESP32 boards.

Integrated protections

The board uPesy ESP32 Wroom DevKit has a protective battery to avoid damaging it. Note that these protections are insufficient to prevent all possible handling errors: the board is not unbreakable.

The board includes the following protections:

• Electrostatic discharge protection on the USB port

• Short circuit protection on the rail \(V_{IN}\) , 5V and 3.3V. Auto-resetting thermal fuses rated for 350 mA are used on the \(V_{IN}\) and 5V. It is, therefore, necessary to avoid drawing too much current on the board. Otherwise, they may be triggered. They are automatically activated and deactivated (polyfuse).

  Warning

  Therefore, you should avoid connecting many motors to the power pins.

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

  Warning

  You can’t supply the ESP32 board directly with 3.3V on pin 3V3.

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

• Reverse polarity protection between \(V_{IN}\) and GND.