This project demonstrates controlling a sequence of 6 LEDs on an Arduino UNO, but with a twist: the core LED control logic is implemented using inline AVR assembly language within the Arduino C++ environment.
This is an evolution of a previous project that accomplished the same LED sequencing task purely in C++. About a month or two ago, it was all digitalWrite(). Now? Now we're talking directly to the metal!
- Sequentially lights up 6 LEDs.
- Utilizes inline AVR assembly for the primary LED control logic.
- Demonstrates bit-shifting (
lsl) in assembly to select which LED to illuminate. - Directly manipulates hardware I/O ports (
PORTB) from assembly. - Shows how to pass data (the
countervariable) from C++ to assembly. - Properly preserves and restores register states (
push/pop) used by the assembly block.
- Arduino UNO (or compatible)
- 6 x LEDs (any color)
- 6 x Current-limiting resistors (e.g., 220Ω - 330Ω, appropriate for your LEDs and 5V)
- Breadboard
- Jumper wires
As seen in the image, the LEDs are connected to Arduino digital pins 8 through 13. These pins correspond to PORTB (PB0 to PB5) on the ATmega328P microcontroller.
- LED 1 (controlled by PB0/D8): Connect Anode to Digital Pin 8 via a resistor. Cathode to GND.
- LED 2 (controlled by PB1/D9): Connect Anode to Digital Pin 9 via a resistor. Cathode to GND.
- LED 3 (controlled by PB2/D10): Connect Anode to Digital Pin 10 via a resistor. Cathode to GND.
- LED 4 (controlled by PB3/D11): Connect Anode to Digital Pin 11 via a resistor. Cathode to GND.
- LED 5 (controlled by PB4/D12): Connect Anode to Digital Pin 12 via a resistor. Cathode to GND.
- LED 6 (controlled by PB5/D13): Connect Anode to Digital Pin 13 via a resistor. Cathode to GND.
Ensure all LED cathodes share a common ground with the Arduino.
- Arduino IDE
- The AVR-GCC toolchain (this is included with the Arduino IDE)