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What are the Functions of the Pro Micro Pinout?

A Pro Micro is a microcontroller board developed by Sparkfun. The Pro Micro is a costly microcontroller board and as such, clones of this board serve as a lower-cost alternative. This board features a micro USB port which allows testing and programming with a computer.

Although the Arduino Pro Micro is very small, its functions are similar to that of a regular Arduino board. You can use this board in a number of applications. Some projects like USB trackpad, electric bike, USB joystick, and automatic pill dispenser make use of the Pro Micro board. Let’s focus more on the Arduino Pro Micro pin out.

Pro Micro Pinout

All input/output power pins of Pro Micro are in two classes. Some pins are dedicated I/o pins while others are for power output or input. Also, the input/output pins feature some unique characteristics such as analog input.

Functions of each Pro Micro Pinout

Let’s look at the functions of each pin.

Power pins

RST: This can restart the Pro Micro board. RST pins must connect to the ground in order to begin a reset. The microcontroller will be “off” until you pull back the reset line to high.

RAW: This is Pro Micro’s unregulated voltage input. If a USB is powering this board, the voltage of this pin will be around 4.8V. Meanwhile, the applied voltage can be about 12V if the board gets power from an external source.

VCC: The on-board ATmega32U4 has a voltage which is known as VCC. The version of the Pro Micro you are using will determine the voltage. If the version is 5V/16MHz or 3.3V/8MHz, the voltage will be 5V or 3.3V respectively. The voltage used by the RAW pin will regulate this voltage.

GND: This is the ground voltage for this board.

I/O Pins

There are 18 input/output pins in the Pro Micro board. These pins serve several purposes, hence they are multipurpose pins. You can use each pin as a digital output or input, to read button presses, or blink LEDs. Furthermore, you can reference these pins in the Arduino IDE through an integer value between the range of 0 and 21.

Nine out of the 18 pins have analog to digital converters and can serve as analog inputs. These pins are good for reading analog devices or potentiometers. Five pins have pulse width modulation function, which enables a form of analog output. These pins have a white circle around them which helps in identifying them.

Other pins like SPI, UART, I2C are available also. They can interface with digital devices such as IMUs, LCDs, and other serial sensors. The Pro Micro features five external interrupts which enable users to initiate a function when the pin becomes low or high. There is a particular interrupt that is triggered when the interrupt-enable pin attaches to an interrupt.

On-Board LEDs

Pro Micro has three LEDs which display different colors. The red LED shows if power is present, the yellow LED indicates when the Pro Micro is receiving USB data (RX), and the green LED shows outgoing USB data (TX).

How do you Power the Pro Micro?

Since the USB functionality of the Pro Micro board is its main feature, the best way to power it is through USB. We will use the 5V Pro Micro as an example. A USB bus will be powering the 5V Pro Micro and a 3.3V Pro Micro will control the power supply from the USB. You can connect the end of the USB cable to a computer or a USB adapter.

However, if there are no USB cables around, you can use VCC or RAW pins to power your Pro Micro. The RAW pin will regulate the power supply it is receiving to an appropriate operating voltage. This voltage should not be more than 12V to be on the safe side.  Also, it should be 1V more than the operating voltage of the Pro Micro i.e (>4V for a Pro Micro of 3V).

Note that the signal will not regulate when the Pro Micro is powered via the VCC pin. You should only make use of the VCC if there is a regulated 5V or 3.3V to connect it. Overall, the requirements of your project will simply determine how you power it. If your project will be powered by battery, you can use a 3.3V Pro Micro.

Operating Frequency and System Voltage of Pro Micros

Pro Micro vary in terms of operating frequency and system voltage. The 5V Pro Micro has an operating frequency of 16MHz while the 3.3V Pro Micro runs at a frequency of 8MHz. There are some factors that determine the maximum voltage of Sparkfun Pro Micro pinout. One of such factors is the operating voltage. For instance, don’t interface a 3.3V Pro Micro with a project that outputs 5V. 

Arduino Pro Micro Pinout

Digital I/O pins

The Pro Micro has 12 digital I/O pins that can serve as output or input according to the requirement. Digital I/O pins can be ON or OFF. These pins get 5V when they are ON and get 0V whenever they are OFF.

Analog pins

These pins are some of Sparkfun Pro Micro pinout. Analog pins get any values unlike digital pins that have two values.

UART pins

They support UART serial communication with two pins that receive and transmit serial data. UART pins are suitable for transfer of serial data.

PMW pins

There are five different PMW channels on the Pro Micro board. Pro Micro creates analog results when you trigger PMW pins.

SPI pins

Pro Micro has an SPI that helps to layout communication between some peripheral devices and microcontroller.

Is Arduino Pro Micro different from Arduino Micro?

The Arduino Pro Micro and Arduino Micro have Atmega32U4 microcontrollers, their functions differ. Pro Micro doesn’t have an ICSP header and a reset button while Arduino Micro has them. Also, pro Micro has fewer pins compared to Arduino Micro. When using the Pro Micro, the SPI interface can’t be in slave mode. This is because Pro Micro can’t offer AREF.


The Pro Micro pinout includes many pins. Each of these pins has their unique purpose. We hope you understand how these pins work.

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