Indicator lights above the d0/rX and d1/tX labels flash, showing that the Arduino is powered and offering a simple light-based output for testing code without connecting any modules.

Indicator lights above the d0/rX and d1/tX labels flash, showing that the Arduino is powered and offering a simple light-based output for testing code without connecting any modules.

How fast does your heart beat? It’s a tough question to answer, because our heart rate changes all the time depending on what we’re doing and how our body is behaving. However, ...