sparkfun MicroMod ESP32 Hook-Up Manual page 6

PinOut Notes
The ESP32 MicroMod has a few quirks. The ESP32's GPIO pins provide a lot of flexibility with what each pin can
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be used for. Whether it's I C, I S, SPI, UART, or PWM, the ESP32 MicroMod can do just about everything!
However, with that flexibility and a fixed number of GPIO pins, the ESP32 isn't able to do it all at the same time.
Below is a list of protocols the ESP32 supports, but pay close attention to the pins used, because some pins are
assigned to two or possibly three functions.
Strapping Pins
One of the unique aspects of the ESP32 is the strapping pins. When the ESP32 comes out of reset, or as power is
supplied, there are a few pins which control the behavior of the board. For a detailed description of these pins,
check out the ESP32 Boot Mode Selection page on espressif's GitHub page. As a summary the strapping pins
are:
GPIO 0
Having GPIO 0 pulled low as the ESP32 comes out of reset will enter the serial bootloader. Otherwise, the board
will run the program stored in flash. On the MicroMod Processor, this pin is pulled high externally through a 10k
resistor, and is connected to the boot button on the carrier boards, which can pull the pin low.
GPIO 2
Having GPIO 2 pulled high as the ESP32 comes out of reset will prevent the board from entering the serial
bootloader. On the MicroMod Processor, this pin is connected to the status LED (active high) and does not
interfere with the board from being able to enter the serial bootloader.
GPIO 12
If driven high, the flash voltage (VDD_SDIO) is set to 1.8V. If unconnected or pulled low, VDD_SDIO is set to 3.3V.
The flash IC used on the MicroMod Processor has a minimum voltage of 2.7V, which would create a brownout
condition and might corrupt the data stored to the flash, or simply prevent the program from running. On the
ESP32 MicroMod Processor, this pin is connected to PWM1.
GPIO 15