Depending on your needs, the following subjects will also be relevant. Tutorials and other reference materials on these are available at the Arduino website.

• Communication buses
  • Serial
  • SPI
  • Wire, a.k.a I2C
• Interrupts
  • External
  • Timers
  • Multiple external
• Watchdog timers
• Libraries
  • 7-segment displays
  • LCD displays
  • Switch matrices