I know this might sound really easy, but is it? We roughly assume all pins are GPIO and then categorize them into Digital and Analog. That’s not quite the case. This episode will explain exactly what they are, the differences, and the use cases.
What is GPIO?
Stands for General Purpose Input and Output. A GPIO pin is a pin that can be configured by software for general-purpose digital input or output. For simplicity, we can call them “interactive pins” because not every pin on a microcontroller is user-programmable. For instance, you have Power & Ground Pins (VCC, 5V, 3.3V and GND) and then System Pins like RESET and oscillator pins.
So, while many digital and analog-capable pins can also be GPIOs, the exact capabilities depend on the microcontroller.
Analog pins
In microcontrollers, there are in-between pins. These pins are both analog-capable and digital. When you write your code, you act like a train conductor flipping a track switch. If you configure the pin as ANALOG_INPUT, the chip routes the electrical signal to the analog converter. If you configure it as DIGITAL_INPUT, it routes it to the digital logic. Meaning, any pin that has analog capabilities can usually also be configured to handle digital logic.
Digital Pins
These are pins that deal with logic states, typically represented as 0s and 1s. Self-explanatory. It accepts digital logic, where you’d delve into the fascinating world of logic gates (ELE308 and MTE304). Now, on a microcontroller, there are certain pins that are strictly digital. Unlike the “in-between” pins, you can’t use them as analog inputs because they don’t have an ADC connection.
An example of this would be PWM pins. Even though PWM is used to simulate an analog output, the physical signal leaving the pin is 100% digital (in its own way).
When to use Digital or Analog Pins.
Digital pins are perfect for components that only have two states; completely ON or completely OFF. For instance, reading states such as detecting if a button is pressed or released, reading data from sensors, or simple outputs such as toggling an LED on and off, triggering buzzers, and then data transfers using various communication protocols.
You’d use PWM-capable pins when controlling components that need variable power or an analog-like output, such as DC motors, dimming LEDs, and sending precise timing pulses to position a mechanism at a specific angle.
And finally, analog inputs are used whenever you need to measure the real world, because it doesn’t do 1s and 0s. An example of this would be potentiometers, where you need to read the position of a knob or joystick, measuring a room’s temperature, and a little advanced use case would be in generating smooth audio signals without using PWM. Don’t worry if anyone is giving you mixed signals, just do a Fourier analysis.😉
