Many developers know that the answer to "How do I debug this microcontroller" is either "JTAG" or "SWD". But what does that mean, exactly? How do you get from "Wiggling wires" to "Programming a chip" and "Halting on breakpoints"? This talk will cover how common debug protocols work starting from signals on physical wires, cover common mechanisms for managing embedded processors, and ending up at talking to various common microcontrollers.