Our next topic concerns connecting an SD card to our Arduino board and reading data from the SD card. We will also learn how to write data to the SD card. Before learning reading or writing, we need to know about data logging. In Arduino, we can connect sensors, and sensors can sense something. For instance, a humidity sensor can measure the humidity in the air, or a temperature sensor can determine the temperature of the environment. All the information from the sensors comes to the Arduino as the fluctuation of a few numbers (usually voltage). We will discuss sensors later. Our point is, the numbers sometimes need to be stored. Let's imagine we need to measure the humidity of different locations and collect data from at least 500 places. We don't want to go to 500 places with our Arduino board connected to the PC. Other than uploading the code and visualizing the output, an Arduino can be used alone. We can connect an SD card and the sensors to the Arduino, and power it with...