Prerequisites _are_ required for this in-depth tour through the intriguing worlds of the Arduino Uno and Mega 2560. Few details are too insignificant to remain unexplored here. Coverage includes the internals of: digital I/O, the I2C bus, the SPI bus, the Hardware Serial Library, STK500, STK500v2, interrupts, the boot sequence from power-on to setup() and loop(), analogWrite(), analogRead(), time and delays, the EEPROM Library, PROGMEM, and F().