ESP32-CAM (AI-Thinker)

Fig. 1. ESP32-CAM (AI-Thinker), 2x8 2.54 mm, 27 x 40.5 mm. Hover or tap a signal to light up every pin that carries it.

• There is no USB. Flashing needs an external USB-to-serial adapter on U0TXD and U0RXD, with GPIO0 shorted to GND to enter the bootloader and the short removed before running. The separate MB baseboard does this for you.
• Every pin on the left header is the SD card interface. GPIO 2, 4, 12, 13, 14 and 15 are HS2_DATA0 to DATA3, CMD and CLK. Use the SD slot and the entire left side is gone; give up the SD slot and you get six pins back.
• GPIO4 is the bright white flash LED as well as HS2_DATA1. It will light whenever you drive it, and it is genuinely blinding. The small red LED on GPIO33 is not on the header.
• GPIO12 is a strapping pin that must be LOW at boot. It is also an SD data line, which is why a card inserted at power-up sometimes stops the board starting.
• Power it from 5 V, not 3.3 V. The camera plus WiFi pulls bursts well over 200 mA and the on-board regulator needs the headroom. Brownout resets during the first camera init are nearly always an undersized supply or a thin USB cable.
• The pin marked 3.3V/5V is an output, selectable by a solder jumper on the back. It is not a second input.
• GPIO16 is connected to the PSRAM on boards that have it, so treat it as unavailable rather than free.
• Realistically free pins after the camera and SD are accounted for: GPIO 1, 3 and 16 if you give up serial and PSRAM, or GPIO 2, 4, 12, 13, 14 and 15 if you give up the SD card. Plan the project around that, not around sixteen holes.

• 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.