Analog input and output

In this section, let us take a look at the commonly used in-built C functions that are used for analog I/O. To begin with we will learn how analog input is measured by the Arduino sketch. An Arduino sketch uses the following function to obtain an analog reading from its analog pins:

analogRead(<pin-number>) 

For example, if we want to read the analog signal value from analog pin A5, we must use the following function call:

int value;                // declare integer variable 
value = analogRead(A5);   // read analog value 

The above function will return an integer value between 0 and 1023, depending upon the voltage value on the pin. The number 0 to 1023 will be proportional to the voltage range of the Arduino Uno board i.e. 0 to 5 volts.

Next we will look at techniques to write analog signals on both analog as well as digital pins. Digital pins that are PWM capable can simulate the behavior of an analog signal, hence the analogWrite() function can be used on a...