Pro Micro & Fio v3 Hookup Guide Datasheet by SparkFun Electronics

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Pro Micro & Fio v3 Hookup Guide

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CONTRIBUTORS: JIMB0

Introduction

Welcome to the new frontier of Arduino-compatible boards, made possible

by the ATmega32U4. No longer does your Arduino need to be harnessed

by an FTDI Cable, or an ATmega8U2, or any chip who’s sole purpose is

acting as an intermediary between your Arduino and your computer.

The SparkFun Pro Micro is a really cool, little development board. It’s an

Arduino-compatible microcontroller, micro-sized, and it accomplishes with

one single chip what old Arduino Unos, Duemilanoves, and Diecimeillas

could never dream of: true USB functionality.

This tutorial also covers the Fio v3, which works a lot like the Pro Micro but

adds features like easy XBee interfacing and LiPo charging.

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Covered In This Tutorial

This tutorial aims to introduce you to both the hardware and firmware sides

of the Pro Micro (and Fio v3). We’ll also dedicate a few pages to helping

install the boards on Windows and Mac. Here’s a summary of what will be

covered:

• Hardware Overview: Pro Micro – An overview of the pinout and

hardware features of the Pro Micro.

• Hardware Overview: Fio v3 – An overview of the pinout and

hardware features of the Fio v3.

• Installing on Windows – How to install the drivers and Arduino addon

on Windows.

• Installing on Mac/Linux – How to install the drivers and Arduino

addon on Mac.

• Example 1: Blinkies – A simple “Hello, world” sketch specifically

suited to the Pro Micro and Fio v3.

• Example 2: HID Mouse and Keyboard – An introduction to the HID

USB capability of the Pro Micro. How to emulate USB keyboards and

mice!

• Troubleshooting and FAQ – Helpful troubleshooting tips and tricks for

getting the most out of the Pro Micro.

Suggested Reading

Before delving into this tutorial, here are some concepts you should be

familiar with. If you’re not, consider checking out the related tutorial first.

• What is Arduino? – An introduction to the Arduino platform and IDE.

• How to Install Arduino – A general installation guide for Arduino.

• Serial Communication – Serial is a great, easy-to-use communication

protocol.

Hardware Overview: Pro Micro

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Before we get into installing and using the Pro Micro, let’s quickly look at

the board – examine its inputs, outputs, and other hardware quirks.

The Pinout

All of the Pro Micro’s I/O and power pins are broken out to two, parallel

headers. Some pins are for power input or output, other pins are dedicated

I/O pins. Further, the I/O pins can have special abilities, like analog input.

Here’s a map of which pin is where, and what special hardware functions it

may have:

Delving a little further into which pins do what…

Power Pins

There are a variety of power and power-related nets broken out:

•RAW is the unregulated voltage input for the Pro Micro. If the board

is powered via USB, the voltage at this pin will be about 4.8V (USB’s

5V minus a schottkey diode drop). On the other hand, if the board is

powered externally, through this pin, the applied voltage can be up to

12V.

•VCC is the voltage supplied to the on-board ATmega32U4. This

voltage will depend on whether you’re using a 3.3V/8MHz Pro Micro

or a 5V/16MHz version, it’ll be either 3.3V or 5V respectively. This

voltage is regulated by the voltage applied to the RAW pin. If the

board is powered through the ‘RAW’ pin (or USB), this pin can be

used as an output to supply other devices.

•RST can be used to restart the Pro Micro. This pin is pulled high by

a 10k&Ohm; resistor on the board, and is active-low, so it must be

connected to ground to initiate a reset. The Pro Micro will remain “off”

until the reset line is pulled back to high.

•GND, of course, is the common, ground voltage (0V reference) for

the system.

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I/O Pins

The Pro Micro’s I/O pins – 18 in all – are multi-talented. Every pin can be

used as a digital input or output, for blinking LEDs or reading button

presses. These pins are referenced in the Arduino IDE via an integer value

between 0 and 21. (The A0-A3 pins can be referenced digitally using either

their analog or digital pin number).

Nine pins feature analog to digital converters (ADCs) and can be used as

analog inputs. These are useful for reading potentiometers or other analog

devices using the analogRead([pin]) function.

There are five pins with pulse width modulation (PWM) functionality, which

allows for a form of analog output using the

analogWrite([pin], [value]) function. These pins are indicated on-board

with a faint, white circle around them.

There are hardware UART (serial), I C, and SPI pins available as well.

These can be used to interface with digital devices like serial LCDs, XBees,

IMUs, and other serial sensors.

The Pro Micro has five external interrupts, which allow you to instantly

trigger a function when a pin goes either high or low (or both). If you attach

an interrupt to an interrupt-enabled pin, you’ll need to know the specific

interrupt that pin triggers: pin 3 maps to interrupt 0, pin 2 is interrupt 1, pin 0

is interrupt 2, pin 1 is interrupt 3, and pin 7 is interrupt 4.

On-Board LEDs

There are three LEDs on the Pro Micro. One red LED indicates whether

power is present.

The other two LEDs help indicate when data is transferring over USB. A

yellow LED represents USB data coming into (RX) the the Pro Micro, and a

green LED indicates USB data going out (TX).

3.3V or 5V? 8MHz or 16MHz?

Pro Micros come in two flavors, which vary by system voltage and

operating frequency. The standard 5V Pro Micro runs at 16MHz, and is

very comparable to an Arduino Leonardo, while the 3.3V version of the Pro

Micro runs at half the speed (to remain in the safe operating zone at the

lower voltage) – 8MHz.

The operating voltage of your Pro Micro determines the maximum allowable

voltage on any of the I/O pins. For example, if you have a 3.3V Pro Micro,

don’t interface it with something that outputs 5V.

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Don’t forget which version you have! We’ll need to differentiate between the

two when we get to uploading code in Arduino. If you’re not sure which

version you have, check the back corner of the board. One of two boxes

should be checked to indicate the operating voltage.

How to Power the Pro Micro

As the Pro Micro’s main feature is its innate USB functionality, the most

common way to power it is via USB. In this setup, a 5V Pro Micro will be

powered directly from the USB bus and a 3.3V Pro Micro will regulate the

5V supply coming in from USB down. The other end of the USB cable can

be connected to either a computer, USB hub, or a USB wall adapter, which

can (in most cases) provide more power.

Alternatively, if your Pro Micro is living out in the wild, out of reach of USB

cables, it can be powered through either the ‘RAW’ or ‘VCC’ pins. A supply

going into the ‘RAW’ pin will be regulated down to the correct operating

voltage (5V or 3.3V). To be safe, it shouldn’t be any higher than 12V, and it

should be at least 1V more than the Pro Micro’s operating voltage (e.g. >6V

for a 5V Pro Micro).

Pro Micro powered through the RAW pin by a set of four, series AA

batteries.

If you power the Pro Micro through the ‘VCC’ pin, keep in mind that this

signal is unregulated. Only use this if you have a clean, regulated 3.3V or

5V supply to connect to it.

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How, exactly, you power your project is up to you and the demands of your

project. If you’re making something battery powered, you may want to opt

for the 3.3V Pro Micro, which could be powered by a LiPo battery or a

couple alkalines.

Hardware Overview: Fio v3

On this page we’ll examine the hardware half of the Fio v3, looking at the

pinout, layout, and schematic of the board.

The Fio v3 is like an elongated Pro Micro. On one end, it’s shape and

pinouts are similar to it’s ATmega32U4 sibling. The other end of the Fio v3

is what makes it unique: a footprint for an XBee on the bottom, and a LiPo

charging circuit on the top.

The Pinout

All of the Fio v3’s pins are broken out to either side of the board. Some pins

are for power input or output, other pins are dedicated I/O pins. Further, the

I/O pins can have special abilities, like analog input, or serial input/output.

Here’s a map of which pin is where, and what special capabilities it may

have:

Power Pins

The pins labeled ‘3.3V’ break out the operating voltage source of the

ATmega32U4. As long as the board is powered through the white JST

connector or USB, this voltage is regulated down to 3.3V. These pins can

be used as outputs to supply 3.3V to other devices.

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The ‘RST’ pin can be used to restart the Fio. This pin is pulled high by a

10kΩ resistor on the board, and is active-low, so it must be connected to

ground to initiate a reset. The Fio will remain off until the reset line is pulled

back to high.

I/O Pins

Many of the Fio’s I/O pins are multi-talented. Every pin can be used as a

digital input or output, for blinking LEDs or reading button presses. These

pins are referenced in the Arduino IDE via an integer value between 0 and

23. (The A0-A10 pins can be referenced digitally via either their analog pin

number or digital pin number).

Eleven pins feature analog to digital converters (ADCs) and can be used as

analog inputs. These are useful for reading potentiometers or other analog

devices using the analogRead([pin]) function.

There are six pins with pulse width modulation (PWM) functionality, which

allows for a form of analog output using the

analogWrite([pin], [value]) function. These pins are indicated on-board

with a faint white circle around the pin.

There are also hardware UART (serial), I C, and SPI pins available. These

can be used to interface with digital devices like serial LCDs, IMUs, and

other serial sensors.

The Fio v3 has five external interrupts, which allow you to instantly trigger a

function when a pin goes either high or low (or both). If you attach an

interrupt to an interrupt-enabled pin, you’ll need to know the specific

interrupt that pin triggers: pin 3 maps to interrupt 0, pin 2 is interrupt 1, pin 0

is interrupt 2, pin 1 is interrupt 3, and pin 7 is interrupt 4.

On-Board LEDs

There are a variety of LEDs on the Fio, the simplest of which is the red

power indicator. Two LEDs towards the bottom – labeled RX and TX – help

indicate when data is transferring to and from the Fio through USB. A blue

LED represents USB data coming into (‘RX’) the the Pro Micro, and a

yellow LED indicates USB data going out (‘TX’).

There are three LEDs tied to the XBee interface in particular: stat, RSSI,

and associate. The red LED labeled ‘ON’ is connected to the XBee’s pin 13

– DIO9 – which is, by default, set to indicate the XBee module’s ON/OFF

status. An ‘RSSI’ LED connects to XBee pin 6 (PWM0) which defaults to

indicate RSSI (received signal strength) – a brighter LED means a stronger

received signal. Lastly, the ‘ASO’ LED connects to XBee pin 15, which will

blink if the module is associated.

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Finally, there’s a yellow LED labeled ‘CHG’ which indicates if an attached

lithium polymer battery is charging. If a battery is not connected to the Fio,

the LED will be in an undefined state, and most likely be illuminated.

How to Power the Fio v3

The suggested power supply for the Fio v3 is any single-cell lithium

polymer (LiPo) battery. These batteries have a nominal voltage of 3.7V,

which is perfect for supplying power to the 3.3V-operating Fio. LiPos are

awesome, because they’re rechargeable and still pack a lot of power into a

tiny space. Any of our single cell LiPos with JST terminators can connect

directly to the Fio’s onboard JST connector.

As an (immobile) alternative to batteries, the Fio can be powered directly

through the USB connector.

Using the LiPo Charger

The Fio v3 has a LiPo charge management circuit (based around the

MCP73831) built onto it, which handles the signal conditioning required to

safely charge a single-cell LiPo battery.

To use the charge circuit, you’ll obviously need a single-cell LiPo battery

plugged into the Fio. Then connect the board up via USB, so the charge

circuit has a primary voltage source to supply charge to the battery.

The ‘CHG’ LED will indicate the status of the battery charge. If it’s on, the

battery is still charging. Once the ‘CHG’ LED goes off, the battery is fully

charged.

The charge circuit is programmed to charge the battery at 500mA, so, to be

safe, the battery should be no smaller than 500mAH in capacity.

Connecting An XBee

The XBee-footprint connectors on the bottom of the Fio v3 are what make it

so unique. This product is designed to provide a simple interface between

Arduino and XBee, as such a few of the XBee pins come wired up to the

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ATmega32U4. Most significantly, the serial interfaces of both devices are

wired – the XBee’s ‘DOUT’ pin is connected to the ATmega32U4’s ‘RX’,

and ‘DIN’ is connected to ‘TX’.

XBee’s are controlled and configured over a serial interface. To learn more

about using XBee’s check out their datasheet and various tutorials for help

getting started with these awesomely simple wireless transceivers.

Installing: Windows

Getting the Pro Micro or Fio v3 set up on your computer and in your

Arduino environment can be difficult. Follow along on this page for a step-

by-step guide through the driver installation and Arduino-enabling process.

Windows Driver Installation

A note to Windows 8 users: Before you can install these drivers, you’ll

need to disable driver signature enforcement. Please check out our quick

Disabling Driver Signature Enforcement tutorial for help with that.

Step 1: Download the Driver

Before plugging your board in, get a head start by downloading the

drivers (check the GitHub Repository for the latest files). The same driver

file works for both the Pro Micro and the Fio v3.

Unzip that zip file, and don’t forget where you’ve left its contents. In that zip

file, you should find an INF file, which contains all the information Windows

needs to install the Pro Micro’s driver.

Step 2: Plug in the Pro Micro / Fio v3

When you initially plug the board in, an “Installing device driver software”

bubble notification should pop up in the lower-right corner of your taskbar.

After the green dot circles the grey box a number of times, you’ll probably

get a sad bubble like this:

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Never fear! Windows just doesn’t know where to find our driver.

Note: Some users have experienced issues when plugging the Pro Micro

into a USB 3.0 port. If you experience issues on USB 3.0 ports, try

switching to use a USB 2.0 port.

Step 3: Open the Device Manager

From here, the most straightforward way to install the driver is through the

Device Manager. To get to the Device Manager, click the Start button, then

open the Control Panel. In the Control Panel, click System and

Maintenance, and then open the Device Manager.

Alternatively, you can open the Run prompt (Windows key+R) and type

‘devmgmt.msc’ and click OK.

In the Device Manager, expand the ‘Other devices’ tree, where you should

find a ‘USB IO Board’ with a yellow warning sign over its icon. Right-click

the ‘USB IO Board’ and select Update Driver Software….

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This should spawn an ‘Update Driver Software - USB IO Board’ window.

Step 4: Finding the Driver

In the first window that pops up, click ‘Browse my computer for driver

software’. On the next window, click ‘Browse…’ to search for the driver

you just downloaded. It should be a folder named ‘SFE32U4_Drivers’. After

you’ve selected the ‘driver’ folder, click OK, then select Next.

Windows will attempt to do its driver install thing, but not before complaining

about the driver being unsigned. It’s safe to select ‘Install this driver

software anyway’ on the warning dialog.

After watching the progress bar beam by a few times, you should get a

happy ‘Windows has successfully updated your driver software’ window.

And the ‘Device Manager’ should have a new entry for the ‘SparkFun Pro

Micro (COM ##)’ (or ‘SparkFun Fio V3 (COM##)’ if you have one of those)

under the ‘Ports’ tree.

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Take note of which COM port your Pro Micro was assigned. We’ll need it

soon.

Installing the Arduino Addon

We’re still not completely ready for Arduino, but this is the final stretch.

Before you can use the ProMicro in the Arduino IDE, you need to enable it

and activate some super-secret Arduino files.

To begin, download this zip folder, and unzip its contents into a

‘hardware’ directory within your Arduino sketchbook.

Note: These Arduino addon files only work with Arduino 1.5 and up. If

you're using an earlier version of Arduino, either update (and get some

cool new features), or download the older version of the Addon.

Where’s your Arduino sketchbook? Well, by default, it should an ‘Arduino’

folder in your home directory, but to double check you can go to ‘File’ >

‘Preferences’ within Arduino and check the ‘Sketchbook location’ text box.

Just make sure you close all Arduino windows once you’re done.

Once you’ve unzipped that folder into the ‘hardware’ folder within your

Arduino sketchbook (you may actually have to create a hardware folder),

your directory structure should look something like this:

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The structure of this directory is critical – it should look something like

“Arduino/hardware/[manufacturer]/[architecture]”, in this case

[manufacturer] is “sparkfun”, and [architecture] is “avr.”

There’s a lot going on in that addon, but one of the most important files is

‘boards.txt’, which will add a few new entries to your ‘Tools > Board’ menu.

To double-check that the board definitions have been added to Arduino,

open up Arduino, and check under the ‘Tools > Board’ menu. There

should be some new entires for ‘SparkFun Pro Micro 8MHz/3.3V’,

‘SparkFun Pro Micro 16MHz/5V’, and other 32U4 boards.

Notice there are two options for Pro Micro - 8MHz and 16MHz. It’s very

important that you select the Pro Micro option that matches your

board’s voltage and speed. Don’t know which board you have? Check the

bottom of the board, where you should find either a ‘5V’ or ‘3.3V’ box

checked.

You should also see your Pro Micro’s COM port under the ‘Tools > Serial

Port’ menu. Select it, and head over to the Example 1 page where we’ll

upload our first piece of code.

Installing: Mac & Linux

If you’re using Mac or Linux, follow the steps below to get your Pro Micro

(or Fio v3) ready to go on your computer. We’re not going to name names

here, but installing the Pro Micro on Mac OS X and Linux is a lot easier

than on other OS’s…

Following these directions is critical to getting your Pro Micro supported

within your Arduino environment!

Board Installation

When you initially plug your Pro Micro into a Mac, it’ll pop up a “Keyboard

Setup Assistant” window. This stems from the Pro Micro’s ability to emulate

an HID USB device (e.g. keyboards and mice) – the Mac thinks your Pro

Micro is a human input device (which it could be! but isn’t yet).

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There’s nothing to configure in this window, so just click the big, red, ‘X’ to

close it.

That’s all there is to it! The CDC (communication device class) portion of

your Pro Micro (the part that handles USB to Serial conversion) should

automatically install on your computer.

Installing the Arduino Addon

In order to use the Pro Micro or Fio v3 in your Arduino IDE, you need to add

a few board definition files to it. That’s what we’ll do in this section. Begin by

downloading the Pro Micro addon files.

Note: These Arduino addon files only work with Arduino 1.5 and up. If

you're using an earlier version of Arduino, either update (and get some

cool new features), or download the older version of the Addon.

With that downloaded, follow these steps to enable the Pro Micro in your

Arduino environment:

1. The addon files are supplied in a zip folder, so you’ll need to extract

the files within first.

2. Find your Arduino sketchbook folder. If you don’t know where it is,

you can locate your sketchbook by looking at the preferences dialog

in your Arduino IDE.

3. If there isn’t already one, create a folder in your sketchbook called

‘hardware’.

4. Copy the ‘sparkfun’ folder that was unzipped in the first step into the

‘hardware’ folder.

◦Your directory structure should look something like

“Arduino/hardware/sparkfun/avr.”

5. Restart Arduino, and look under the Tools > Board menu. You should

see a few new options, including ‘SparkFun Pro Micro 5V/16MHz’,

‘SparkFun Pro Micro 3.3V/8MHz’, and ‘'SparkFun Fio V3 3.3V/8MHz’.

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If the boards are visible, select the option that matches your board. If you

have a Pro Micro, make sure you select the correct operating speed and

voltage! Then head over to the next page where we’ll upload our first

sketch!

Example 1: Blinkies!

The Arduino-standard Blink sketch won’t have any visible effect on the Pro

Micro – there’s no LED on pin 13. In fact, the only LEDs on the board are

the power indicator, and RX/TX blinkies. Unlike other Arduino boards,

though, we can control the RX/TX LEDs in our sketch. So let’s get blinking!

Upload the RX/TX Blinky Sketch

Copy and paste the code below, and upload* it to your Pro Micro.

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/*ProMicroTestCode

by:NathanSeidle

modifiedby:JimLindblom

SparkFunElectronics

date:September16,2013

license:PublicDomainpleaseusethiscodehoweveryo

u'dlike.

It'sprovidedasalearningtool.

ThiscodeisprovidedtoshowhowtocontroltheSparkFun

ProMicro'sTXandRXLEDswithinasketch.Italsoserves

toexplainthedifferencebetweenSerial.print()and

Serial1.print().

int RXLED=17;//TheRXLEDhasadefinedArduinopin

//TheTXLEDwasnotsolucky,we'llneedtousepredefined

//macros(TXLED1,TXLED0)tocontrolthat.

//(WecouldusethesamemacrosfortheRXLEDtooRXLED1,

//andRXLED0.)

void setup()

{

pinMode(RXLED,OUTPUT);//SetRXLEDasanoutput

//TXLEDissetasanoutputbehindthescenes

Serial.begin(9600);//Thispipestotheserialmonitor

Serial1.begin(9600);//ThisistheUART,pipestosensorsatt

achedtoboard

}

void loop()

{

Serial.println("Helloworld");//Print"HelloWorld"toth

eSerialMonitor

Serial1.println("Hello!");//Print"Hello!"overhardwareU

ART

digitalWrite(RXLED,LOW);//settheLEDon

TXLED0;//TXLEDisnottiedtoanormallycontrolledpin

delay(1000);//waitforasecond

digitalWrite(RXLED,HIGH);//settheLEDoff

TXLED1;

delay(1000);//waitforasecond

}

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With the code uploaded you should see the RX and TX LEDs take turns

blinking on and off every second. You can also open up the serial monitor

(set to 9600 bps) and see every programmer’s favorite two-word phrase.

Understanding the Sketch

The RX LED is tied to Arduino’s pin 17. You can control it just as you would

any other digital pin. Set it as an OUTPUT , and

digitalWrite([pin],[level]) it HIGH or LOW . The TX LED was not

provided as an Arduino-defined pin, unfortunately, so you’ll have to use a

pair of macros to control it. TXLED1 turns the LED on, and TXLED0 turns

the LED off.

In that sketch, you’ll also notice a pair of Serial initialization statements:

Serial.begin(9600) , Serial1.begin(9600) . That ‘1’ makes a huge

difference. Think of the Pro Micro having two separate serial ports. The one

without the ‘1’ is for communication to and from the computer over USB;

this is what is visible in the Serial Monitor. The Serial1 port is a bonafide,

hardware UART, where your Pro Micro can talk to any serial-enabled piece

of hardware.

If you open up the Serial Monitor, you should only see ‘Hello world’

printed. ‘Hello!’ is being sent out over the hardware UART, where,

presumably, nothing is listening. This begs the age-old question: “if a Pro

Micro is saying ‘Hello!’ over the hardware serial port, and nothing is there to

hear it, does the Pro Micro really say anything at all?.”

Why Does My Board Re-Enumerate Every

Upload?

In order to communicate serially, the Pro Micro emulates a virtual serial

port. Actually, it emulates two different serial ports – one for the bootloader,

and one for the sketch. Since the bootloader and sketch run individually.

Only one of these serial ports is visible at any one time.

When you click ‘Upload’ in the Arduino IDE, the Pro Micro resets itself and

starts its bootloader program. (The bootloader is a low-level program on

the Pro Micro which enables self-programming via serial.) To our operating

system, the bootloader looks like a completely different device, so it gets its

own serial port number. While the Pro Micro is being programmed, the

bootloader serial port will be open. When the sketch upload is finished, the

bootloader will exit, that serial port will be closed, and the regular Pro Micro

serial port will open up.

What this all boils down to is the fact that you have to be patient with Pro

Micros. Every time you upload a new sketch, your OS will need to work its

driver magic before you can open up the COM port. This can take a few

seconds after the code has finished uploading.

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* Note for Windows users: The first time you upload a sketch, it may fail

and give you an error. On top of that Windows will pop up that familiar

‘Device driver software was not successfully installed’ notification. Don’t let

this worry you too much. If you get the error, wait about a minute, and try

uploading again.

Hopefully the upload will succeed the second time, but if it continues to fail,

check out the how to enter the bootloader section of the FAQ. Windows

needs to install the same driver we’ve already installed for the Pro Micro’s

bootloader, but it’s unable to get everything set up before the bootloader

exits.

Example 2: HID Mouse and Keyboard

By far, the Pro Micro’s most revolutionary feature (as far as Arduinos go) is

its true USB functionality. The Pro Micro can be programmed to emulate

any USB device you could imagine. You can even program it to act just like

a mouse, keyboard, or other HID-class USB device.

What is HID? It’s one of the many defined USB device classes. Every USB

device is assigned a class, which defines what its general purpose is. There

are loads of classes – printers, hubs, speakers, and webcams to mention a

few, but in this example we’ll be emulating HID – Human Interface Device.

The ATmega32U4 takes care of the USB-hardware hurdle, but we’ve still

got to clear the firmware one. Time for some example code!

USB Keyboards Made Simple

To emulate a USB keyboard, we’ll be making use of the Keyboard class.

Here are some of the functions made available to us by this class:

•Keyboard.write(char) - This function will send a single character

over USB. The character passed can be any standard, printable,

ASCII-defined character: 0-9, a-z, A-Z, space, symbols, etc. Here’s

an example line of code:

Keyboard.write('z')//Thiswillsendasingle'z'charactertoyourcomputer.

•Keyboard.print(string) - If you need to perform a series a

Keyboard.write() ’s, consider using just a single

Keyboard.print() . This works similar to Serial.print() – give it a

string of characters and it’ll send that stream of characters over USB.

Keyboard.println(string) is also defined, if you want a

newline/linefeed to close out your string. An example:

Keyboard.print("Hello,world");//This'llsendyourcomputeran'H',followedby'e',followedby...

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•Keyboard.press(byte) and Keyboard.release(byte) give you more

precise control over key presses. They do exactly what you’d expect.

One presses a button down, the other releases a button. Make sure

you release any buttons you press, otherwise you’ll encounter some

wiggyness on your computer.

That’s it. You don’t need to include any libraries or anything, just invoke any

of those functions. Here’s an example sketch to try it out:

int buttonPin=9;//Setabuttontoanypin

void setup()

{

pinMode(buttonPin,INPUT);//Setthebuttonasaninput

digitalWrite(buttonPin,HIGH);//Pullthebuttonhigh

}

void loop()

{

if (digitalRead(buttonPin)== 0)//ifthebuttongoeslow

{

Keyboard.write('z');//senda'z'tothecomputerviaKe

yboardHID

delay(1000);//delaysotherearen'takajillionz's

}

}

In this sketch, connecting pin 9 to ground will make the Pro Micro spit out

a ‘z’ character. If you have a simple, momentary button handy, tie one end

to pin 9 and the other to ground. Otherwise, just use a wire to short 9 to

GND.

After a Keyboard.write() or Keyboard.print() function has been

performed by the Pro Micro, your computer will have to decide what to do

with it. What your computer does with that character, or string of characters,

is entirely dependent on what program it’s running at the time. If you have a

text editor open and active, it’ll print it out there.

USB Mouse Functionality

That covers about half of USB HID library. How about we add a mouse to

the mix now? Implementing a USB HID mouse requires a few more

functions, but it’s still crazy simple. There are five functions provided by

Arduino’s HID class that can be used to implement a mouse:

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•Mouse.move(x, y, wheel) tells the computer to move the mouse a

certain number of pixels along either the x, y and/or wheel axis. Each

variable can be any value between -128 and +127, with negative

numbers moving the cursor down/left, positive numbers move the

right/up.

•Mouse.press(b) sends a down-click on a button or buttons. The

button(s) will remain “pressed” until you call Mouse.release(b) . The

bvariable is a single byte, each bit of which represents a different

button. You can set it equal to any of the following, or OR (|) them

together to click multiple buttons at once:

◦MOUSE_LEFT - Left Mouse button

◦MOUSE_RIGHT - Right Mouse button

◦MOUSE_MIDDLE - Middle mouse button

◦MOUSE_ALL - All three mouse buttons

•Mouse.click(b) sends a down-click (press) followed immediately by

an up-click (release) on button(s) b. For example, to click the left

and right buttons simultaneously, try this:

Mouse.click(MOUSE_LEFT|MOUSE_RIGHT);//Pressandreleasetheleftandrightmousebuttons

Here’s some example code to show off these functions:

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/*HIDJoystickMouseExample

by:JimLindblom

date:1/12/2012

license:MITLicenseFeelfreetousethiscodeforanyp

urpose.

Norestrictions.Justkeepthislicenseifyougoontous

ethis

codeinyourfutureendeavors!Reuseandshare.

Thisisverysimplisticcodethatallowsyoutoturnthe

SparkFunThumbJoystick(http://www.sparkfun.com/products/9

032)

intoanHIDMouse.Theselectbuttononthejoystickisse

tup

asthemouseleftclick.

*/

int horzPin= A0;//Analogoutputofhorizontaljoystickpin

int vertPin= A1;//Analogoutputofverticaljoystickpin

int selPin=9;//selectbuttonpinofjoystick

int vertZero,horzZero;//Storestheinitialvalueofeacha

xis,usuallyaround512

int vertValue,horzValue;//Storescurrentanalogoutputof

eachaxis

const int sensitivity= 200;//Highersensitivityvalue=sl

owermouse,shouldbe<=about500

int mouseClickFlag=0;

void setup()

{

pinMode(horzPin,INPUT);//Setbothanalogpinsasinputs

pinMode(vertPin,INPUT);

pinMode(selPin,INPUT);//setbuttonselectpinasinput

digitalWrite(selPin,HIGH);//Pullbuttonselectpinhigh

delay(1000);//shortdelaytoletoutputssettle

vertZero= analogRead(vertPin);//gettheinitialvalues

horzZero= analogRead(horzPin);//Joystickshouldbeinne

utralpositionwhenreadingthese

}

void loop()

{

vertValue= analogRead(vertPin) vertZero;//readvertica

loffset

horzValue= analogRead(horzPin) horzZero;//readhorizon

taloffset

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Page 22 of 27

if (vertValue!= 0)

Mouse.move(0,vertValue/sensitivity,0);//movemouseo

nyaxis

if (horzValue!= 0)

Mouse.move(horzValue/sensitivity,0,0);//movemouseo

nxaxis

if ((digitalRead(selPin)== 0)&& (!mouseClickFlag))//if

thejoystickbuttonispressed

{

mouseClickFlag=1;

Mouse.press(MOUSE_LEFT);//clicktheleftbuttondown

}

else if ((digitalRead(selPin))&&(mouseClickFlag))//ifthe

joystickbuttonisnotpressed

{

mouseClickFlag=0;

Mouse.release(MOUSE_LEFT);//releasetheleftbutton

}

}

This sketch is set up so that an analog joystick connected to analog pins A0

and A1 can be used to move your mouse cursor.

The loop() of this code continuously monitors the horizontal and vertical

analog values of the joystick and sends the Mouse.move() command based

on what it reads. It’ll move the mouse in steps, depending on what the

sensitivity variable is set to. With sensitivity set to 2, the cursor will move in

either 1 or 2 pixel steps.

The select switch on the joystick is used to control the mouse left click.

Notice this code is using Mouse.press() and Mouse.release() , rather

than just calling a single Mouse.click() . This requires a bit more coding,

but it allows you to do things like drag-and-drop, double click, etc.

For more HID example code, check out the Arduino-supplied examples

under the ‘File’ > ‘Examples’ > ‘09.USB’ menu.

Troubleshooting and FAQ

On this page you’ll find troubleshooting tips and FAQs. Here’s a directory of

the subjects covered:

•Troubleshooting

◦Serial Port Not Showing Up in “Tools > Board” menu

◦How to Reset to Bootloader

◦How to Revive a “Bricked” Pro Micro

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h ‘Pvess noomanev mud! comma” mode am code user code Page 23 of 27

•Frequently Asked Questions

◦What are VIDs and PIDs?

◦How Can I Change the VID and PID on an ATmega32U4?

◦Why Does my ATmega32U4 Board Show up Twice in the

Device Manager?

◦How Does the IDE Know Which COM Port to Use?

◦How Do I Reinstall the Bootloader?

Serial Port Not Showing Up in ‘Tools > Board’

The Pro Micro can be a finicky little thing. There are a few series of events

that can lead to its serial port being removed from the Arduino IDE’s Serial

Port selection menu. If you can’t see your Pro Micro’s serial port, give these

steps a try:

1. Close all Arduino windows. (Don’t forget to save!)

2. Unplug Pro Micro from your computer.

3. Wait a few seconds for the device to be detached.

4. Plug Pro Micro back in.

5. Open Arduino back up, check the Serial Ports menu again.

Reset to Bootloader

We ship the Pro Micro with a modified version of the Arduino Leonardo

bootloader, with one major enhancement. When a Leonardo (or any device

using the “stock” bootloader) is externally reset, it goes back into the

bootloader…and waits there eight seconds before it starts running the

sketch. For some embedded projects, waiting eight seconds before a

program runs isn’t acceptable, so we modified the bootloader run time.

Leonardo bootloader on reset functionality.

When a Pro Micro is externally reset (by pulling the RST pin low), it’ll only

briefly (<750ms) start the bootloader before continuing on to the sketch. If

you need the bootloader to run longer, resetting twice quickly will get the

Pro Micro to enter bootloader mode for eight seconds.

Pro Micro and Fio v3 reset functionality. Press reset twice, quickly to enter

bootloader mode.

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Page 24 of 27 A USB Device Nok Recognized “ X one am: use dmts ll'uhed n. rimming-nah” mum-mm um mam am run recognize n Fm .mm. 'm whiny INS pmlm mun"; msugL

Resetting the Pro Micro’s, in particular, can be tricky, because there’s no

reset button. The ‘RST’ pins needs to be connected to ground to initiate a

reset. This can be done with a small piece of wire, or an externally

connected button.

Why would you need to enter bootloader mode in the first place. Glad you

asked…

How to Revive a “Bricked” Pro Micro

Incorporating all of the USB tasks on a single chip is an awesome feature

that makes the Pro Micro and boards like it truly unique. But it also places

more stress on a single chip, and if anything goes wrong with that chip, the

board becomes nearly unusable. It’s not uncommon for Pro Micro’s to

become “bricked” and unprogrammable. But, in most cases, the bricking is

reversible!

The most common source of Pro Micro “bricking” is uploading code to it

with an incorrectly set board (e.g. programming a 16MHz/5V Pro Micro

with the board set to 8MHz/3.3V). Also, make sure your sketch doesn’t

mess with the ATmega32U4’s PLLCSR register, or any other register that

sets up USB functionality on the ATmega32U4. The Pro Micro will actually

take code compiled for the wrong operating speed, but when it tries to re-

enumerate, you’ll be greeted with a notification like this:

To revive the Pro Micro, you’ll need to find a way to upload a sketch to it

with the board option correctly set. We can do this with a little help from the

bootloader.

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Page 25 of 27

First, you’ll need to set the serial port to the bootloader. But that port is

only visible when the board is in bootloader mode, so pull the reset line low

twice quickly to invoke the bootloader reset feature discussed above. On

Pro Micro’s, or other devices which don’t have a reset button, you can

either use a wire to quickly short ‘RST’ to ‘GND’ twice, or wire up a

temporary reset button. While the Pro Micro is in the bootloader change

the ‘Tools > Serial Port’ menu to the bootloader COM port. Quick! You’ve

only got eight seconds. On Windows, the bootloader’s COM port number is

usually one number higher than the Pro Micro’s regular port number.

With the serial port set, we’re just about ready to re-upload our sketch. But

first, double check that the board is correctly set. Then reset to

bootloader again, and quickly upload your sketch. Again, you’ll have to be

quick…you’ve only got eight seconds. It may help to press the Upload

keybind – CTRL+U / CMD+U – immediately after resetting.

It can take a few tries to get the timing right. Since the code has to compile

first, it may help to hit upload first and then reset.

Frequently Asked Questions

If you’re having technical difficulties with your Pro Micro or Fio v3, see if any

of the answers to these FAQs help. If not, please get in touch with our tech

support team.

What are VID and PIDs?

VID is short for ‘Vender Identification’ and PID is short for ‘Part

Identification’. In other words, this pair of IDs defines the device. This is

how your computer knows what you’ve plugged in, what drivers to use with

it, what COM port is assigned to it, etc. All native USB devices have a

VID/PID.

All SparkFun ATmega32U4 boards share the same VID – 0x1B4F, and

they all have unique PIDs. 5V Pro Micros lay claim to PIDs 0x9205 and

0x9206 (one for the bootloader, one for the sketch). 3.3V Pro Micros will

show up as 0x9203 and 0x9204 for bootloader and sketch, respectively.

And the Fio v3 has 0xF100 and 0xF101.

How Can I Change the VID and PID on an ATMega32U4

Board?

Every time you upload code the VID and PID are uploaded to the device.

These values are located in the ‘boards.txt’ file and will therefore be

determined by the board you have selected. Keep in mind that if you select

the wrong board you will get the wrong VID/PID uploaded which means the

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Page 26 of 27

computer can’t recognize, and program the board. The VID/PID for the

bootloader is part of the bootloader file. To change this you will need to

recompile the bootloader with the new VID/PID, and upload it.

Why Does my ATMega32U4 Board Show up Twice in Device

Manager?

Both the bootloader and the sketch have their own VID/PIDs. When you

plug in a board the bootloader starts running for a few seconds, and you will

see the board show up in Device Manager based on those VID/PIDs. After

a few seconds, the sketch will start running, and you will see Device

Manager disconnect from the bootloader and connect to the sketch.

How Does the IDE Know Which COM Port to Use?

When the IDE resets the board, the COM port is disconnected from the

computer. The IDE then looks for a new COM port. This is the port it uses.

This is one of those weird things Arduino did to get things to work on this

chip.

How Do I Reinstall the Bootloader?

Check out or reinstalling the bootloader tutorial, which should work for both

ATMega32U4 and ATMega328 boards. If you have the tools to do so,

reinstalling the bootloader is often easier then trying to stay in the

bootloader. Since reinstalling the bootloader puts the board back in factory

settings this will reset the VID/PID numbers allowing your board to work

again.

Resources & Going Further

Thanks for checking out our Pro Micro and Fio v3 Hookup Guide! If you’re

looking for more resources related to these boards, here are some links:

• Pro Micro Schematic

• Pro Micro EAGLE Files

• Fio v3 Schematic

• Fio v3 EAGLE Files

• ATmega32U4 Datasheet

• ATmega32U4 Arduino Addon GitHub Repository

Going Further

Thanks for reading along with our Pro Micro hookup guide! Hopefully now

you’re fully prepared to begin using the Pro Micro in a project of your own.

Here are some tutorials that might be worth checking out as you continue

down the rabbit hole:

• Exploring XBees and XCTU

• Arduino Programming 101

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Page 27 of 27 htrps://lcam.sparkfun.cKym/tutorials/pro-micro--ﬁo—v3—hookup—guidc 2/12/2015

• Arduino Comparison Guide

• Connecting Arduino to Processing

• Using the Arduino Pro Mini 3.3V

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Pro Micro & Fio v3 Hookup Guide Datasheet by SparkFun Electronics

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