The ESP32 is a low-cost microcontroller System-on-a-Chip (SoC). An SoC is a microcontroller that integrates a computer's or device's components into a single chip. The ESP32 includes a microprocessor, memory, various interfaces and peripherals, and integrated WiFi and Bluetooth capabilities. To use the ESP32 microcontroller in various industrial products and applications like temperature controllers, motor controls, object sensing/detection, and visual alarm indicators, an understanding of basic input/output electronic circuit interfaces is required. A basic I/O primer will allow the development and testing of control application code to be created by the software developer. This talk will explain basic I/O interfacing circuit techniques using electrical and electronic components like tactile pushbutton switches, transistors, and sensors. The talk will include operating electromechanical and solid state relays (SSR) using an ESP32 microcontroller. Circuit diagrams and basic microcontroller code will be presented in this talk.