ESP32 DevKit V1 (30-pin)

Fig. 1. ESP32 DevKit V1 (30-pin), 2x15 2.54 mm, 51 x 28 mm. Hover or tap a signal to light up every pin that carries it.

• GPIO34, 35, 36 and 39 are input only. No output driver and no internal pull-up or pull-down, so every button on them needs an external resistor.
• ADC2 (GPIO 0, 2, 4, 12, 13, 14, 15, 25, 26, 27) is taken over by the radio. Anything you read while WiFi is connected has to be on ADC1: GPIO 32 to 39.
• GPIO12 must be LOW at boot. It selects the flash voltage, and a pull-up there stops the board starting at all. It is the worst pin on the module to hang a device on.
• Other strapping pins: GPIO0 low enters flash mode (the BOOT button), GPIO2 must be low or floating, GPIO5 and GPIO15 are pulled high at boot and emit a PWM burst as they do.
• GPIO6 to GPIO11 wire to the SPI flash inside the module. They are not on the 30-pin header, and the 38-pin version that does expose them should not be used.
• Any output-capable pin can do PWM: the LEDC block has 16 channels and routes to any GPIO, so the usual PWM pin lists do not apply.
• VIN takes 5 V. The onboard regulator handles about 600 mA, and the radio pulls 250 mA spikes, so a thin USB cable shows up as random reboots.

• Drive a pin and read one

  ESP-IDF v5

  #include "driver/gpio.h"
  
  gpio_reset_pin(GPIO_NUM_2);    /* clears any leftover mux setting */
  gpio_set_direction(GPIO_NUM_2, GPIO_MODE_OUTPUT);
  gpio_set_level(GPIO_NUM_2, 1);
  
  gpio_config_t in = {
      .pin_bit_mask = 1ULL << GPIO_NUM_4,
      .mode         = GPIO_MODE_INPUT,
      .pull_up_en   = GPIO_PULLUP_ENABLE,
      .intr_type    = GPIO_INTR_NEGEDGE,
  };
  gpio_config(&in);

  pin_bit_mask is 64-bit. Writing 1 << GPIO_NUM_34 instead of 1ULL << overflows a 32-bit int and silently configures nothing.

Table 1. Pin assignments.