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--- arduino:arduino_crash_course:digital_input [2012/11/12 18:29] – [Software debouncing] mithat
+++ arduino:arduino_crash_course:digital_input [2017/12/06 01:13] (current) – [Digital Input] mithat
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 The Arduino literature refers to "digital" inputs, and while this is strictly accurate, a better name for these kinds of inputs is "Boolean" or "logical" inputs. However, we will use the more common "digital input" to avoid confusion.
-An Arduino digital input is one that responds to two different levels; anything above a certain voltage (but lower than the Arduino's supply voltage) is considered HIGH, and anything below a certain voltage (but not below 0 volts) is considered LOW. Anything in between is not defined. The threshold levels will vary with specific Arduino implementation, so to learn what they are you should consult the documentation.
+An Arduino digital input is one that responds to two different levels: anything above a certain threshold is considered HIGH, and anything below a certain voltage is considered LOW. Anything in between is not defined. The threshold levels will vary with specific Arduino implementation, so to learn what they are you should consult the documentation.
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-Typically, digital input signals are designed so that when HIGH they have a value equal to the supply voltage and when LOW they are equal to 0 volts.
+Digital output signals are typically designed so that when HIGH they have a value equal to the supply voltage and when LOW they are equal to 0 volts.
-We've already seen an example of Arduino digital inputs in the [[arduino:arduino_crash_course:basic_interaction|Basic Interaction]] examples. Here is the LightSwitchPullup2.ino example but using some additional variable types that better match the role of the variables.
+We've already seen an example of Arduino digital inputs in the [[arduino:arduino_crash_course:basic_interaction|Basic Interaction]] examples. Here is the ''LightSwitchPullup2.ino'' example but using an additional variable type that better matches the role of the ''buttonState'' variable. Variables of type ''boolean'' can store the values ''true'' and ''false''. Since the button has two states, pushed and not pushed, using a variable that can store only two states, ''true'' and ''false'' makes sense. We have chosen to let ''true'' correspond to the button's "pushed" and ''false'' correspond to "not pushed." It is typical for variables used to store digital inputs be of type ''boolean''.
+We have also added the ''const'' modifier to the ''pushButtonPin'' and  ''ledPin'' variables to say that their values won't change in the program. In fact, when you add the ''const'' modifier to a variable declaration, the value of the variable //can't// change.
 <file c LightSwitchPullup2a.ino>