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KEY TAKE AWAY POINTS:
Typically just 2 values
In programming, usually as integer 1/0
On physical circuit, usually as voltage HIGH (3V) / LOW(GND)
Outputting a digital signal "digital write pin [ ] to (0/1)"
Inputting a digital signal "digital read pin [ ]"
Never leave a digital PIN floating, undefined digital input/output pin ends as random result
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Analog Signal, Digital Signal
Analog Signal, Digital Signal
Signals as in Life
Signals as in Life
Snapshot from Dictionary boxes on Google
Signals in Electronics
Signals in Electronics
In electronics, a signal is carried by electromagnetic or electrical current, often represented by a time-varying Voltage that is carrying information.
2 types of signals: Analog and Digital signals.
Analog Signal
Analog Signal
Represents continuous values. At any given time it represents a value within a continuous range. Produce a smooth and continuous curve, no discrete value changes.
Often used to represent changes in natural light, sound, temperature, position, pressure, or other physical phenomena.
Digital Signal
Digital Signal
Represents data as a sequence of discrete values. At any given time it can only take on at the most one of a finite number of values.
Used in all digital electronics, including computing equipment and data transmission devices. Typical case in computer is simply only 2 values.
Digital Signal Presentation
Digital Signal Presentation
For Digital Signaling, there must be a clear answer from the 2 values! Unspecified answer means uncertain random result, which creates troubles!
Programming
Integer number 1/0
Physics
Voltage HIGH/LOW
Input-Process-Output Model
Input-Process-Output Model
Floating Pin❓ - Random Input❗
Floating Pin❓ - Random Input❗
"digital read pin [ ]" reads in the input from pin (voltage), which must be safely managed. Idle input from pin (voltage) is floating, unless it's explicitly pulled up/down.
Pull Up/Down by Software (internal)
Pull Up/Down by Software (internal)
Use software to activate built-in pull up/down resistor, not always available.
Pull Up/Down by Hardware (external)
Pull Up/Down by Hardware (external)
Pull it up/down by a pulling-resistor wired externally.
De-bouncing when it Matters
De-bouncing when it Matters
Digital input often has "bouncing issue", keep in mind about the non-ideal physical phenomenon, de-bounce the jitter as needed.
Initialize on Start
Initialize on Start
Before any "digital write pin [ ] to (0/1)", the initial output to pin (voltage) is floating!
It's good practice to always initialize the starting state on start.
Persisting Output - As it was, until Changed
Persisting Output - As it was, until Changed
After a "digital write pin [ ] to (0/1)", the resulted output to pin (voltage) persists, unless changed by another new command
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