I have an ESP-EYE v2.1 module and wanted to connect some more peripherals using GPIO. However, the board doesn't have any GPIO pins available. There are some soldering taps available, labeled DOUT, DIN, CLK and CS, but there is no documentation about these pins. By tracing the leads and referencing the esp32 datasheet I managed to find the following scheme: DOUT -> MTDI -> GPIO 12 (GPIO12) DIN -> GPIO 2 (GPIO2) CLK -> GPIO 0 (GPIO0) CS -> GPIO 19 (GPIO19) Ground is connected to the bottom of the side button, so I now soldered two wires and am using an external LED flash to make pictures using CS and the GND connections. I hope this helps you!