Adafruit LED Backpacks User Manual

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Adafruit LED Backpacks

Created by Melissa LeBlanc-Williams

https://learn.adafruit.com/adafruit-led-backpack

Last updated on 2022-10-03 01:18:04 PM EDT

©Adafruit Industries Page 1 of 161

Overview

1.2" 8x8 Matrix

Assembly

Arduino Setup

• Mini 8x8 Matrix Software

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Setting Individual Pixels

• Filling the Entire Matrix

• Shifting the Matrix

• Displaying an Image (Pillow Only)

0.8" 8x8 Matrix

Assembly

Arduino Wiring and Setup

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Setting Individual Pixels

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• Filling the Entire Matrix

• Shifting the Matrix

• Displaying an Image (Pillow Only)

1.2" 16x8 Matrix

Arduino Setup

• 16x8 Matrix Software

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Setting Individual Pixels

• Filling the Entire Matrix

• Shifting the Matrix

• Displaying an Image (Pillow Only)

0.54" Alphanumeric Backpack

Pinouts

• STEMMA QT Revision-Only Features

• STEMMA QT Connectors

• On LED and LED Jumper

• Original and STEMMA QT Version Features

• Header Pin Through-Hole Pads

• Display Pin Through-Hole Pads

• HT16K33 Matrix Driver

• Address Jumper Pins

Assembly

• Attaching the Backpack

• Attaching Header

• Prepare the header strip:

• Add the Backpack:

Arduino Wiring and Setup

• Downloading the Arduino Library

• Wiring STEMMA QT Version

• Wiring Original Version

• Load Demo

• Library Reference

• ASCII data

• Writing Data

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CircuitPython Wiring and Setup

• Wiring STEMMA QT Version

• Wiring Original Version

• HT16K33 Library Installation

Python Wiring and Setup

• Wiring

• Wiring STEMMA QT Version

• Wiring Original Version

• Setup

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Printing Text

• Printing Numbers

• Printing Hexidecimal Values

• Setting Individual Characters

• Setting Individual Segments

• Filling all Segments

• Scrolling Display Manually

• Displaying an Automatic Scrolling Marquee

• Full Example

0.56" 7-Segment Backpack

Assembly and Arduino Wiring

Arduino Setup

• Seven-Segment Backpack Firmware

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Printing Text

• Printing Numbers

• Printing Hexidecimal Values

• Setting Individual Characters

• Setting Individual Segments

• Filling all Segments

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• Scrolling Display Manually

• Displaying the Colon

• Displaying an Automatic Scrolling Marquee

1.2" 7-segment Backpack

Assembly

Arduino Wiring and Setup

• Arduino Wiring - R3 and later

• Arduino Due and Other 3.3v Processors

• Arduino "Classic" Wiring

• Seven-Segment Backpack Firmware

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Printing Text

• Printing Numbers

• Printing Hexidecimal Values

• Setting Individual Characters

• Setting Individual Segments

• Filling all Segments

• Scrolling Display Manually

• Displaying the Colon

• Setting the Left-Side Dots

• Setting the AM/PM Indicator

• Displaying an Automatic Scrolling Marquee

103

107

110

112

Bi-Color 8x8 Matrix

Assembly

Arduino Setup

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

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117

118

121

124

126

• Python Installation of HT16K33 Library

• Pillow Library

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Setting Individual Pixels

• Filling the Entire Matrix

• Shifting the Matrix

• Displaying an Image (Pillow Only)

Bi-Color 24 Bargraph

Assembly

• Soldering on breadboard pins

Arduino Wiring and Setup

CircuitPython Wiring and Setup

• Wiring

• Library Setup

• Bundle Install

Python Wiring and Setup

• Wiring

• Setup

• Python Installation of HT16K33 Library

128

131

132

138

141

143

CircuitPython and Python Usage

• Initialization

• Setting the Brightness

• Setting the Blink Rate

• Setting Individual Bars

• Filling the Entire Bargraph

Connecting Multiple Backpacks

• Wire it Up

• Configure the Address

Changing I2C Address

• Changing Addresses

• Changing the address in your code

F.A.Q.

Downloads

• Software

• Files

• HT16K33 8x16 LED Backpack Breakout

• 8x8 0.8" LED Backpack

• 8x8 1.2" LED Backpack

• 8x8 1.2" Bi-Color LED Backpack

• 16x8 1.2" LED Backpacks

• 0.56" 7-Segment LED Backpack STEMMA QT

145

146

148

151

152

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• Quad 0.56" 7-Segment Original

• Quad 0.54" 14-segment Alphanumeric STEMMA QT Version

• Quad 0.54" 14-segment Alphanumeric Original Version

• Quad 1.2" 7-Segment

• Bicolor 24-Bargraph

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©Adafruit Industries Page 8 of 161

Overview

What's better than a single LED? Lots of LEDs! A fun way to make a small display is to

use an 8x8 matrix(https://adafru.it/aLG) or a 4-digit 7-segment display(https://

adafru.it/aLH). Matrices like these are 'multiplexed' - so to control 64 LEDs you need

16 pins. That's a lot of pins, and there are driver chips like the MAX7219(http://

adafru.it/453) that can control a matrix for you but there's a lot of wiring to set up and

they take up a ton of space. Here at Adafruit we feel your pain! After all, wouldn't it be

awesome if you could control a matrix without tons of wiring? That's where these

adorable LED matrix backpacks come in.

We have them in quite a few flavors!

Adorable Mini 8x8(https://adafru.it/ttf)

•

Classic 1.2" 8x8 (round and square dots)(https://adafru.it/ttA)

•

Mini 1.2" 16x8 (round and square dots)(https://adafru.it/JpF)

•

4-digit 0.56" 7-segment(https://adafru.it/ttB)

•

4-digit 1.2" 7-segment(https://adafru.it/ttC)

•

4-digit 0.54" 14-segment Alphanumeric(https://adafru.it/ttD)

•

Bi-color 8x8(http://adafru.it/902)

•

Bi-color Bargraph(http://adafru.it/1721)

•

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The matrices use a driver chip that does all the heavy lifting for you: They have a built

in clock so they multiplex the display. They use constant-current drivers for ultra-

bright, consistent color (the images above are photographed at the dimmest setting

to avoid overloading our camera!), 1/16 step display dimming, all via a simple I2C

interface. The backpacks come with address-selection jumpers so you can connect

up to four mini 8x8's or eight 7-segments (or a combination, such as four mini 8x8's

and four 7-segments, etc) on a single I2C bus.

The product kit comes with a fully tested and assembled LED backpack, a 4-pin

header and the matrix of your choice. A bit of soldering is required to attach the

matrix onto the backpack but it's very easy to do and only takes about 5 minutes.

©Adafruit Industries Page 10 of 161

Of course, in classic Adafruit fashion, we also have a detailed tutorial showing you

how to solder, wire and control the display. We even wrote a very nice library for the

backpacks so you can get running in under half an hour, displaying images on the

matrix or numbers on the 7-segment. If you've been eyeing matrix displays but

hesitated because of the complexity, his is the solution you've been looking for!

1.2" 8x8 Matrix

This version of the LED backpack is designed for the 1.2" 8x8 matrices. They measure

only 1.2"x1.2" so its a shame to use a massive array of chips to control it. This

backpack solves the annoyance of using 16 pins or a bunch of chips by having an I2C

constant-current matrix controller sit neatly on the back of the PCB. The controller

chip takes care of everything, drawing all 64 LEDs in the background. All you have to

do is write data to it using the 2-pin I2C interface. There are two address select pins

so you can select one of 8 addresses to control up to 8 of these on a single 2-pin I2C

bus (as well as whatever other I2C chips or sensors you like). The driver chip can 'dim'

the entire display from 1/16 brightness up to full brightness in 1/16th steps. It cannot

dim individual LEDs, only the entire display at once.

Assembly

These instruction apply to the 1.2" Matrix only! If you have a Bi-Color or 0.8"

square matrix, follow the links on the left side of the page.

©Adafruit Industries Page 11 of 161

When you buy a pack from Adafruit, it

comes with the fully tested and assembled

backpack as well as a 8x8 matrix in one of

the colors we provide (say, red, yellow or

green). You'll need to solder the matrix

onto the backpack but its an easy task.

WATCH OUT! THE MATRIX MUST BE

INSTALLED THE RIGHT WAY!

First look for the line of text on the side of

the LED matrix

WATCH OUT! THE MATRIX MUST BE

INSTALLED THE RIGHT WAY!

Find the corner of the backpack with a

filled in dot. Make sure that the text on the

side of the matrix is on the same side as

the filled dot

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WATCH OUT! THE MATRIX MUST BE

INSTALLED THE RIGHT WAY!

Slide the matrix into the backpack and flip

it over. Triple check that the text is on the

same side as the From Adafruit text

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Solder in all 16 pins

Then clip the matrix leads short

©Adafruit Industries Page 14 of 161

Now you're ready to wire it up to a

microcontroller. We'll assume you want to

use a 4pin header. You can also of course

solder wires directly. Place a 4-pin piece of

header with the LONG pins down into the

breadboard.

That's it! now you're ready to run the firmware!

Arduino Setup

Place the soldered backpack on top of the

header.

Solder the four pins

You can use these with a 3.3v or 5v microcontroller. Just connect the VCC+ pin is

the same voltage as the logic on your microcontroller.

©Adafruit Industries Page 15 of 161

Mini 8x8 Matrix Software

We wrote a basic library to help you work with the mini 8x8 matrix backpack. The

library is written for the Arduino and will work with any Arduino as it just uses the I2C

pins. The code is very portable and can be easily adapted to any I2C-capable micro.

Wiring to the matrix is really easy

ConnectCLK to the I2C clock - on Arduino UNO thats Analog #5 (or SCL), on the

•

Leonardo its Digital #3, on the Mega its digital #21

ConnectDAT to the I2C data - on Arduino UNO thats Analog #4 (or SDA), on the

•

Leonardo its Digital #2, on the Mega its digital #20

ConnectGNDto common ground

•

ConnectVCC+to power - 5V is best but 3V also seems to work for 3V

•

microcontrollers.

Next, download theAdafruit LED Backpacklibrary and theAdafruit GFXlibrary from

the Arduino library manager.

Open up the Arduino library manager:

Search for theAdafruit LED Backpacklibrary and install it

Search for theAdafruit GFXlibrary and install it

©Adafruit Industries Page 16 of 161

If using an earlier version of the Arduino IDE (prior to 1.8.10), also locate and install Ad

afruit_BusIO (newer versions will install this dependency automatically).

You should now be able to select the

File→Examples→Adafruit_LEDBackpack→matrix88 example sketch. Upload it to your

Arduino as usual. You should see a basic test program that goes through a bunch of

different drawing routine

We also have a great tutorial on Arduino library installation at:

http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use(https://

adafru.it/aYM)

Once you're happy that the matrix works, you can write your own sketches. The 8x8

matrix supports everything the Adafruit GFX library - drawing pixels, lines, rectancles,

circles, triangles, roundrects, and small bitmaps. For more details check out the GFX

page which will detail all of the GFX routines(https://adafru.it/aPx).

All the drawing routines only change the display memory kept by the Arduino. Don't

forget to call writeDisplay() after drawing to 'save' the memory out to the matrix via

I2C.

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There are also a few small routines that are special to the matrix:

setBrightness(brighness)- will let you change the overall brightness of the entire

•

display. 0 is least bright, 15 is brightest and is what is initialized by the display

when you start. You can call this function at any time to change the brightness of

the -entire- display

blinkRate(rate) - You can blink the entire display. 0 is no blinking. 1, 2 or 3 is for

•

display blinking.You can call this function at any time to change the blink rate of

the -entire- display

The default orientation for graphics

commands on this display places pixel

(0,0) at the top-left when the header is at

the left and Adafruit logo at the right. To

use the matrix as shown above (header at

top, logo at bottom), call

matrix.setRotation(3) before issuing

graphics commands.

CircuitPython Wiring and Setup

Wiring

It's easy to use LED Matrices with CircuitPython and the Adafruit CircuitPython

HT16K33(https://adafru.it/u1E) library. This module allows you to easily write

CircuitPython code to control the display.

You can use this sensor with any CircuitPython microcontroller board.

We'll cover how to wire the LED Matrix to your CircuitPython microcontroller board.

First assemble your LED Matrix.

Connect the LED Matrix to your microcontroller board as shown below.

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Microcontroller 3Vto LED Matrix VIN

Microcontroller GNDto LED MatrixGND

Microcontroller SCLto LED MatrixSCL

Microcontroller SDAto LED MatrixSDA

Download Fritzing Object

https://adafru.it/Ify

Library Setup

To use the LED backpackwith yourAdafruit CircuitPython(https://adafru.it/BlM)board

you'll need to install theAdafruit_CircuitPython_HT16K33(https://adafru.it/u1E) library

on your board.

First make sure you are running thelatest version of Adafruit CircuitPython(https://

adafru.it/tBa)for your board. Next you'll need to install the necessary librariesto use

the hardware--read below and carefully follow the referenced steps to find and install

these libraries from Adafruit's CircuitPython library bundle(https://adafru.it/zdx).

Bundle Install

For express boards that have extra flash storage, like the Feather/Metro M0 express

and Circuit Playground express, you can easily install the necessary libraries with Ada

fruit's CircuitPython bundle(https://adafru.it/zdx). This is an all-in-one package that

includes the necessary libraries to use the LED backpack display with CircuitPython.

For details on installing the bundle, read about CircuitPython Libraries(https://

adafru.it/ABU).

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/

Metro M0 basic you'll need to manually install the necessary libraries(https://adafru.it/

ABU) from the bundle:

adafruit_ht16k33•

©Adafruit Industries Page 19 of 161

adafruit_bus_device

•

If your board supports USB mass storage, like the M0-based boards, then simply drag

the files to the board's file system.Note on boards without external SPI flash, like a

Feather M0 or Trinket/Gemma M0, you might run into issues on Mac OSX with hidden

files taking up too much space when drag and drop copying,see this page for a

workaround(https://adafru.it/u1d).

Before continuing make sure your board's lib folder or root filesystem has at least

theadafruit_ht16k33 andadafruit_bus_devicefolders/modules copied over.

Python Wiring and Setup

Wiring

It's easy to use LED Matrices with Python and the Adafruit CircuitPython HT16K33(htt

ps://adafru.it/u1E) library. This library allows you to easily write Python code to control

the display.

We'll cover how to wire the LED Matrix to your Raspberry Pi. First assemble your LED

Matrix.

Since there's dozens of Linux computers/boards you can use we will show wiring for

Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to

see whether your platform is supported(https://adafru.it/BSN).

Connect the LED Matrix as shown below to your Raspberry Pi.

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Raspberry Pi 3.3VtoLED Matrix VIN

Raspberry Pi GNDto LED MatrixGND

Raspberry Pi SCLto LED MatrixSCL

Raspberry Pi SDAto LED MatrixSDA

Download Fritzing Object

https://adafru.it/Ifz

Setup

You'll need to install the Adafruit_Blinka library that provides the CircuitPython

support in Python. This may also require enabling I2C on your platform and verifying

you are running Python 3. Since each platform is a little different, and Linux changes

often, please visit the CircuitPython on Linux guide to get your computer ready(https:

//adafru.it/BSN)!

Python Installation of HT16K33 Library

Once that's done, from your command line run the following command:

pip3 install adafruit-circuitpython-ht16k33

•

If your default Python is version 3 you may need to run 'pip' instead. Just make sure

you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

If that complains about pip3 not being installed, then run this first to install it:

sudo apt-get install python3-pip

•

©Adafruit Industries Page 21 of 161

Pillow Library

We also need PIL, the Python Imaging Library, to allow using text with custom fonts.

There are several system libraries that PIL relies on, so installing via a package

manager is the easiest way to bring in everything:

sudo apt-get install python3-pil

•

That's it. You should be ready to go.

CircuitPython and Python Usage

The following section will show how to control the LED backpackfrom the board's

Python prompt / REPL. You'll walk through how to control the LED display and learn

how to use the CircuitPython module built for the display.

Firstconnect to the board's serial REPL(https://adafru.it/Awz)so you are at the

CircuitPython>>>prompt.

Initialization

First you'll need to initialize the I2C bus for your board. It's really easy, first import the

necessary modules. In this case, we'll use board and Matrix8x8 .

Then just use board.I2C() to create the I2C instance using the default SCL and

SDA pins (which will be marked on the boards pins if using a Feather or similar

Adafruit board).

Then to initialize the matrix, you just pass i2c in.

import board from adafruit_ht16k33.matrix import Matrix8x8

i2c = board.I2C() matrix = Matrix8x8(i2c)

If you bridged the address pads on the back of the display, you could pass in the

address. The addresses for the HT16K33 can range between 0x70 and 0x77

depending on which pads you have bridged, with 0x70 being used if you haven't

©Adafruit Industries Page 22 of 161

bridged any of them. For instance, if you bridge only the A0 pad, you would use

0x71 like this:

matrix = Matrix8x8(i2c, address=0x71)

Setting the Brightness

You can set the brightness of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/16 increments betw

een 0 and 1.0 with 1.0 being the brightest. So to set the display to half brightness, you

would use the following:

matrix.brightness = 0.5

Setting the Blink Rate

You can set the blink rate of the display, but changing it will set the brightness of the

entire display and not individual pixels. If can be adjusted in 1/4 incrementsbetween 0

and 3with 3 being the fastest blinking. So to set the display to blink at full speed, you

would use the following:

matrix.blink_rate = 3

Setting Individual Pixels

To set individual pixels to on, you simply treat the matrix object as a

multidimensional list and set it to 1.

matrix[0, 0] = 1 matrix[4, 4] = 1 matrix[7, 7] = 1

Filling the Entire Matrix

To fill the entire matrix, just use the fill() function and pass in either 0 or 1 depending

on whether you want all pixels off or on. For instance, if you wanted to set everything

to on, you would use:

matrix.fill(1)

©Adafruit Industries Page 23 of 161

Shifting the Matrix

To shift the pixels on the matrix, there are 5 functions you can use. The main function,

called shift(), is used to shift the pixels, up, down, left, right, or even diagonally. By

passing a positive number, it will shift the pixels right/up and passing a negative

number will shift them left/down. For instance:

matrix.shift(2, 0) # shift pixels to the right by 2 matrix.shift(-1, 0) # shift pixels to the left by 1 matrix.shift(0, -3) # shift pixels down by 3 matrix.shift(-2, 2) # shift pixels left by 2 and up by 2

You can pass True as a third parameter to loop all the pixels that get shifted off over

to the other side.

matrix.shift(2, 0, True) # loop pixels to the right by 2 matrix.shift(-1, 0, True) # loop pixels to the left by 1 matrix.shift(0, -3, True) # loop pixels down by 3 matrix.shift(-2, 2, True) # loop pixels left by 2 and up by 2

Additionally, there are a few convenience functions that will shift the pixels by one.

These can also be passed a value of True to loop the pixels.

matrix.shift_up() # Shift pixels up matrix.shift_left() # Shift pixels left matrix.shift_down() # Shift pixels down matrix.shift_right() # Shift pixels right matrix.shift_up(True) # Loop pixels up matrix.shift_left(True) # Loop pixels left matrix.shift_down(True) # Loop pixels down matrix.shift_right(True) # Loop pixels right

Displaying an Image (Pillow Only)

Additionally, when using with the Raspberry Pi, you can use the Pillow library to

display an image to the Matrix. The image will need to be the same exact size as the

Matrix. In this case, it should be 8x8 pixels. As an example, you can save the image

below asmyimage.png.

Download Image

https://adafru.it/ICR

©Adafruit Industries Page 24 of 161

Then if you want to display the image calledmyimage.png, you would use something

like this:

import board from PIL import Image from adafruit_ht16k33 import matrix

matrix = matrix.Matrix8x8(board.I2C())

image = Image.open("myimage.png") matrix.image(image)

0.8" 8x8 Matrix

This version of the LED backpack is designed for these very cute miniature 8x8

matrices. They measure only 0.8"x0.8" so its a shame to use a massive array of chips

to control it. This backpack solves the annoyance of using 16 pins or a bunch of chips

by having an I2C constant-current matrix controller sit neatly on the back of the PCB.

The controller chip takes care of everything, drawing all 64 LEDs in the background.

All you have to do is write data to it using the 2-pin I2C interface. There are two

address select pins so you can select one of 4 addresses to control up to 4 of these

on a single 2-pin I2C bus (as well as whatever other I2C chips or sensors you like).

The driver chip can 'dim' the entire display from 1/16 brightness up to full brightness in

1/16th steps. It cannot dim individual LEDs, only the entire display at once.

©Adafruit Industries Page 25 of 161

Assembly

These instruction apply to the 0.8" Matrix only! If you have a Bi-Color or 1.2"

square matrix, follow the links on the left side of the page.

When you buy a pack from Adafruit, it

comes with the fully tested and assembled

backpack as well as a 8x8 matrix in one of

the colors we provide (say, red, yellow or

green). You'll need to solder the matrix

onto the backpack but its an easy task.

©Adafruit Industries Page 26 of 161

Remove the parts from packaging and

place the LED matrix OVER the silkscreen

side. It can go 'either way' - the matrix is

symmetric so as long as it goes onto the

front it will work in any orientation. Do not

solder the matrix over the chip on the back

of the backpack - it will not work then!

Turn the backpack over so its sitting flat on

the matrix.

Solder all 16 pins.

©Adafruit Industries Page 27 of 161

Clip the long pins.

Now you're ready to wire it up to a

microcontroller. We'll assume you want to

use a 4pin header. You can also of course

solder wires directly. Place a 4-pin piece of

header with the LONG pins down into the

breadboard.

©Adafruit Industries Page 28 of 161

Place the soldered backpack on top of the

header.

Solder 'em!

That's it! now you're ready to run the firmware!

Arduino Wiring and Setup

You can use these with a 3.3v or 5v microcontroller. Just connect the VCC+ pin is

the same voltage as the logic on your microcontroller.

We wrote a basic library to help you work with the mini 8x8 matrix backpack. The

library is written for the Arduino and will work with any Arduino as it just uses the I2C

pins. The code is very portable and can be easily adapted to any I2C-capable micro.

Wiring to the matrix is really easy

ConnectCLK to the I2C clock - on Arduino UNO thats Analog #5 (or SCL), on the

•

Leonardo its Digital #3, on the Mega its digital #21

ConnectDAT to the I2C data - on Arduino UNO thats Analog #4 (or SDA), on the

•

Leonardo its Digital #2, on the Mega its digital #20

ConnectGNDto common ground

•

©Adafruit Industries Page 29 of 161

ConnectVCC+to power - 5V is best but 3V also seems to work for 3V

•

microcontrollers.

Next, download theAdafruit LED Backpacklibrary and theAdafruit GFXlibrary from

the Arduino library manager.

Open up the Arduino library manager:

Search for theAdafruit LED Backpack library and install it

Search for theAdafruit GFXlibrary and install it

If using an earlier version of the Arduino IDE (prior to 1.8.10), also locate and install Ad

afruit_BusIO (newer versions will install this dependency automatically).

Once you've restarted you should be able to select the

File→Examples→Adafruit_LEDBackpack→matrix88 example sketch. Upload it to your

Arduino as usual. You should see a basic test program that goes through a bunch of

different drawing routines

©Adafruit Industries Page 30 of 161

We also have a great tutorial on Arduino library installation at:

http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use(https://

adafru.it/aYM)

Once you're happy that the matrix works, you can write your own sketches. The 8x8

matrix supports everything the Adafruit GFX library - drawing pixels, lines, rectancles,

circles, triangles, roundrects, and small bitmaps. For more details check out the GFX

page which will detail all of the GFX routines(https://adafru.it/aPx).

All the drawing routines only change the display memory kept by the Arduino. Don't

forget to call writeDisplay() after drawing to 'save' the memory out to the matrix via

I2C.

There are also a few small routines that are special to the matrix:

setBrightness(brighness)- will let you change the overall brightness of the entire

•

display. 0 is least bright, 15 is brightest and is what is initialized by the display

when you start

blinkRate(rate) - You can blink the entire display. 0 is no blinking. 1, 2 or 3 is for

•

display blinking.

©Adafruit Industries Page 31 of 161

CircuitPython Wiring and Setup

Wiring

It's easy to use LED Matrices with CircuitPython and the Adafruit CircuitPython

HT16K33(https://adafru.it/u1E) library. This module allows you to easily write

CircuitPython code to control the display.

You can use this sensor with any CircuitPython microcontroller board.

We'll cover how to wire the LED Matrix to your CircuitPython microcontroller board.

First assemble your LED Matrix.

Connect the LED Matrix to your microcontroller board as shown below.

Microcontroller 3Vto LED Matrix VIN

Microcontroller GNDto LED MatrixGND

Microcontroller SCLto LED MatrixSCL

Microcontroller SDAto LED MatrixSDA

Download Fritzing Object

https://adafru.it/Ify

Library Setup

To use the LED backpackwith yourAdafruit CircuitPython(https://adafru.it/BlM)board

you'll need to install theAdafruit_CircuitPython_HT16K33(https://adafru.it/u1E) library

on your board.

First make sure you are running thelatest version of Adafruit CircuitPython(https://

adafru.it/tBa)for your board. Next you'll need to install the necessary librariesto use

©Adafruit Industries Page 32 of 161

the hardware--read below and carefully follow the referenced steps to find and install

these libraries from Adafruit's CircuitPython library bundle(https://adafru.it/zdx).

Bundle Install

For express boards that have extra flash storage, like the Feather/Metro M0 express

and Circuit Playground express, you can easily install the necessary libraries with Ada

fruit's CircuitPython bundle(https://adafru.it/zdx). This is an all-in-one package that

includes the necessary libraries to use the LED backpack display with CircuitPython.

For details on installing the bundle, read about CircuitPython Libraries(https://

adafru.it/ABU).

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/

Metro M0 basic you'll need to manually install the necessary libraries(https://adafru.it/

ABU) from the bundle:

adafruit_ht16k33

•

adafruit_bus_device

•

If your board supports USB mass storage, like the M0-based boards, then simply drag

the files to the board's file system.Note on boards without external SPI flash, like a

Feather M0 or Trinket/Gemma M0, you might run into issues on Mac OSX with hidden

files taking up too much space when drag and drop copying,see this page for a

workaround(https://adafru.it/u1d).

Before continuing make sure your board's lib folder or root filesystem has at least

theadafruit_ht16k33 andadafruit_bus_devicefolders/modules copied over.

©Adafruit Industries Page 33 of 161

Python Wiring and Setup

Wiring

It's easy to use LED Matrices with Python and the Adafruit CircuitPython HT16K33(htt

ps://adafru.it/u1E) library. This library allows you to easily write Python code to control

the display.

We'll cover how to wire the LED Matrix to your Raspberry Pi. First assemble your LED

Matrix.

Since there's dozens of Linux computers/boards you can use we will show wiring for

Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to

see whether your platform is supported(https://adafru.it/BSN).

Connect the LED Matrix as shown below to your Raspberry Pi.

Raspberry Pi 3.3VtoLED Matrix VIN

Raspberry Pi GNDto LED MatrixGND

Raspberry Pi SCLto LED MatrixSCL

Raspberry Pi SDAto LED MatrixSDA

Download Fritzing Object

https://adafru.it/Ifz

Setup

You'll need to install the Adafruit_Blinka library that provides the CircuitPython

support in Python. This may also require enabling I2C on your platform and verifying

you are running Python 3. Since each platform is a little different, and Linux changes

often, please visit the CircuitPython on Linux guide to get your computer ready(https:

//adafru.it/BSN)!

©Adafruit Industries Page 34 of 161

Python Installation of HT16K33 Library

Once that's done, from your command line run the following command:

pip3 install adafruit-circuitpython-ht16k33

•

If your default Python is version 3 you may need to run 'pip' instead. Just make sure

you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

If that complains about pip3 not being installed, then run this first to install it:

sudo apt-get install python3-pip

•

Pillow Library

We also need PIL, the Python Imaging Library, to allow using text with custom fonts.

There are several system libraries that PIL relies on, so installing via a package

manager is the easiest way to bring in everything:

sudo apt-get install python3-pil

•

That's it. You should be ready to go.

CircuitPython and Python Usage

The following section will show how to control the LED backpackfrom the board's

Python prompt / REPL. You'll walk through how to control the LED display and learn

how to use the CircuitPython module built for the display.

Firstconnect to the board's serial REPL(https://adafru.it/Awz)so you are at the

CircuitPython>>>prompt.

Initialization

First you'll need to initialize the I2C bus for your board. It's really easy, first import the

necessary modules. In this case, we'll use board and Matrix8x8 .

©Adafruit Industries Page 35 of 161

Then just use board.I2C() to create the I2C instance using the default SCL and

SDA pins (which will be marked on the boards pins if using a Feather or similar

Adafruit board).

Then to initialize the matrix, you just pass i2c in.

import board from adafruit_ht16k33.matrix import Matrix8x8

i2c = board.I2C() matrix = Matrix8x8(i2c)

If you bridged the address pads on the back of the display, you could pass in the

address. The addresses for the HT16K33 can range between 0x70 and 0x77

depending on which pads you have bridged, with 0x70 being used if you haven't

bridged any of them. For instance, if you bridge only the A0 pad, you would use

0x71 like this:

matrix = Matrix8x8(i2c, address=0x71)

Setting the Brightness

You can set the brightness of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/16 increments betw

een 0 and 1.0 with 1.0 being the brightest. So to set the display to half brightness, you

would use the following:

matrix.brightness = 0.5

Setting the Blink Rate

You can set the blink rate of the display, but changing it will set the brightness of the

entire display and not individual pixels. If can be adjusted in 1/4 incrementsbetween 0

and 3with 3 being the fastest blinking. So to set the display to blink at full speed, you

would use the following:

matrix.blink_rate = 3

©Adafruit Industries Page 36 of 161

Setting Individual Pixels

To set individual pixels to on, you simply treat the matrix object as a

multidimensional list and set it to 1.

matrix[0, 0] = 1 matrix[4, 4] = 1 matrix[7, 7] = 1

Filling the Entire Matrix

To fill the entire matrix, just use the fill() function and pass in either 0 or 1 depending

on whether you want all pixels off or on. For instance, if you wanted to set everything

to on, you would use:

matrix.fill(1)

Shifting the Matrix

To shift the pixels on the matrix, there are 5 functions you can use. The main function,

called shift(), is used to shift the pixels, up, down, left, right, or even diagonally. By

passing a positive number, it will shift the pixels right/up and passing a negative

number will shift them left/down. For instance:

You can pass True as a third parameter to loop all the pixels that get shifted off over

to the other side.

Additionally, there are a few convenience functions that will shift the pixels by one.

These can also be passed a value of True to loop the pixels.

matrix.shift_up() # Shift pixels up matrix.shift_left() # Shift pixels left matrix.shift_down() # Shift pixels down

©Adafruit Industries Page 37 of 161

matrix.shift_right() # Shift pixels right matrix.shift_up(True) # Loop pixels up matrix.shift_left(True) # Loop pixels left matrix.shift_down(True) # Loop pixels down matrix.shift_right(True) # Loop pixels right

Displaying an Image (Pillow Only)

Additionally, when using with the Raspberry Pi, you can use the Pillow library to

display an image to the Matrix. The image will need to be the same exact size as the

Matrix. In this case, it should be 8x8 pixels. As an example, you can save the image

below asmyimage.png.

Download Image

https://adafru.it/ICR

Then if you want to display the image calledmyimage.png, you would use something

like this:

import board from PIL import Image from adafruit_ht16k33 import matrix

matrix = matrix.Matrix8x8(board.I2C())

image = Image.open("myimage.png") matrix.image(image)

©Adafruit Industries Page 38 of 161

1.2" 16x8 Matrix

With the 16x8 LED Matrix we've doubled your project's matrix capacity by making it

super easy to get two separate 8x8 matrices onto one handy board! This version of

the LED backpack is designed for two of the 1.2" 8x8 matrices. They measure only

1.2"x1.2" so its a shame to use a massive array of chips to control it. This backpack

solves the annoyance of using 32 pins or a bunch of chips by having an I2C constant-

current matrix controller sit neatly on the back of the PCB. The controller chip takes

care of everything, drawing all 128 LEDs in the background. All you have to do is write

data to it using the 2-pin I2C interface. There are two address select pins so you can

select one of 8 addresses to control up to 8 of these on a single 2-pin I2C bus (as

well as whatever other I2C chips or sensors you like). The driver chip can 'dim' the

entire display from 1/16 brightness up to full brightness in 1/16th steps. It cannot dim

individual LEDs, only the entire display at once.

Assembling the 1.2" 16x8 backpack is nearly the same as the 1.2" 8x8, so you can follo

w that page(https://adafru.it/LAT) for directions,only difference is there’s two matrices

to install now.

The printed-on edge of the matrices face the white dots on the PCB, and there’s a

single set of address selection pads; the pair is addressed as one larger unit, not set

independently.

©Adafruit Industries Page 39 of 161

Arduino Setup

You can use these with a 3.3v or 5v microcontroller. Just connect the VCC+ pin is

the same voltage as the logic on your microcontroller.

16x8 Matrix Software

We wrote a basic library to help you work with the 16x8 matrix backpack. The library is

written for the Arduino and will work with any Arduino as it just uses the I2C pins. The

code is very portable and can be easily adapted to any I2C-capable micro.

Wiring to the matrix is really easy

ConnectCLK to the I2C clock - on Arduino UNO thats Analog #5 (or SCL), on the

•

Leonardo its Digital #3, on the Mega its digital #21

ConnectDAT to the I2C data - on Arduino UNO thats Analog #4 (or SDA), on the

•

Leonardo its Digital #2, on the Mega its digital #20

ConnectGNDto common ground

•

ConnectVCC+to power - 5V is best but 3V also seems to work for 3V

•

microcontrollers.

Next, download theAdafruit LED Backpacklibrary and theAdafruit GFXlibrary from

the Arduino library manager.

Open up the Arduino library manager:

©Adafruit Industries Page 40 of 161

Search for theAdafruit LED Backpacklibrary and install it

Search for theAdafruit GFXlibrary and install it

If using an earlier version of the Arduino IDE (prior to 1.8.10), also locate and install Ad

afruit_BusIO (newer versions will install this dependency automatically).

You should now be able to select the

File→Examples→Adafruit_LEDBackpack→matrix88 example sketch. Upload it to your

Arduino as usual. You should see a basic test program that goes through a bunch of

different drawing routine

We also have a great tutorial on Arduino library installation at:

http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use(https://

adafru.it/aYM)

©Adafruit Industries Page 41 of 161

Once you're happy that the matrix works, you can write your own sketches. The 8x8

matrix supports everything the Adafruit GFX library - drawing pixels, lines, rectancles,

circles, triangles, roundrects, and small bitmaps. For more details check out the GFX

page which will detail all of the GFX routines(https://adafru.it/aPx).

All the drawing routines only change the display memory kept by the Arduino. Don't

forget to call writeDisplay() after drawing to 'save' the memory out to the matrix via

I2C.

There are also a few small routines that are special to the matrix:

setBrightness(brighness)- will let you change the overall brightness of the entire

•

display. 0 is least bright, 15 is brightest and is what is initialized by the display

when you start. You can call this function at any time to change the brightness of

the -entire- display

blinkRate(rate) - You can blink the entire display. 0 is no blinking. 1, 2 or 3 is for

•

display blinking.You can call this function at any time to change the blink rate of

the -entire- display

©Adafruit Industries Page 42 of 161

The default orientation for graphics

commands on this display places pixel

(0,0) at the top-left when the header is at

the left and Adafruit logo at the right. To

use the matrix as shown above (header at

top, logo at bottom), call

matrix.setRotation(3) before issuing

graphics commands.

CircuitPython Wiring and Setup

Wiring

It's easy to use LED Matrices with CircuitPython and the Adafruit CircuitPython

HT16K33(https://adafru.it/u1E) library. This module allows you to easily write

CircuitPython code to control the display.

You can use this sensor with any CircuitPython microcontroller board.

We'll cover how to wire the LED Matrix to your CircuitPython microcontroller board.

First assemble your LED Matrix.

Connect the LED Matrix to your microcontroller board as shown below.

Microcontroller 3Vto LED Matrix VIN

Microcontroller GNDto LED MatrixGND

Microcontroller SCLto LED MatrixSCL

Microcontroller SDAto LED MatrixSDA

Download Fritzing Object

https://adafru.it/IB5

©Adafruit Industries Page 43 of 161

Library Setup

To use the LED backpackwith yourAdafruit CircuitPython(https://adafru.it/BlM)board

you'll need to install theAdafruit_CircuitPython_HT16K33(https://adafru.it/u1E) library

on your board.

First make sure you are running thelatest version of Adafruit CircuitPython(https://

adafru.it/tBa)for your board. Next you'll need to install the necessary librariesto use

the hardware--read below and carefully follow the referenced steps to find and install

these libraries from Adafruit's CircuitPython library bundle(https://adafru.it/zdx).

Bundle Install

For express boards that have extra flash storage, like the Feather/Metro M0 express

and Circuit Playground express, you can easily install the necessary libraries with Ada

fruit's CircuitPython bundle(https://adafru.it/zdx). This is an all-in-one package that

includes the necessary libraries to use the LED backpack display with CircuitPython.

For details on installing the bundle, read about CircuitPython Libraries(https://

adafru.it/ABU).

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/

Metro M0 basic you'll need to manually install the necessary libraries(https://adafru.it/

ABU) from the bundle:

adafruit_ht16k33

•

adafruit_bus_device

•

If your board supports USB mass storage, like the M0-based boards, then simply drag

the files to the board's file system.Note on boards without external SPI flash, like a

Feather M0 or Trinket/Gemma M0, you might run into issues on Mac OSX with hidden

files taking up too much space when drag and drop copying,see this page for a

workaround(https://adafru.it/u1d).

Before continuing make sure your board's lib folder or root filesystem has at least

theadafruit_ht16k33 andadafruit_bus_devicefolders/modules copied over.

©Adafruit Industries Page 44 of 161

Python Wiring and Setup

Wiring

It's easy to use LED Matrices with Python and the Adafruit CircuitPython HT16K33(htt

ps://adafru.it/u1E) library. This library allows you to easily write Python code to control

the display.

We'll cover how to wire the LED Matrix to your Raspberry Pi. First assemble your LED

Matrix.

Since there's dozens of Linux computers/boards you can use we will show wiring for

Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to

see whether your platform is supported(https://adafru.it/BSN).

Connect the LED Matrix as shown below to your Raspberry Pi.

Raspberry Pi 3.3Vto LED MatrixVIN

Raspberry Pi GNDto LED MatrixGND

Raspberry Pi SCLto LED MatrixSCL

Raspberry Pi SDAto LED MatrixSDA

©Adafruit Industries Page 45 of 161

Download Fritzing Object

https://adafru.it/IB6

Setup

You'll need to install the Adafruit_Blinka library that provides the CircuitPython

support in Python. This may also require enabling I2C on your platform and verifying

you are running Python 3. Since each platform is a little different, and Linux changes

often, please visit the CircuitPython on Linux guide to get your computer ready(https:

//adafru.it/BSN)!

Python Installation of HT16K33 Library

Once that's done, from your command line run the following command:

pip3 install adafruit-circuitpython-ht16k33

•

If your default Python is version 3 you may need to run 'pip' instead. Just make sure

you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

If that complains about pip3 not being installed, then run this first to install it:

sudo apt-get install python3-pip

•

Pillow Library

We also need PIL, the Python Imaging Library, to allow using text with custom fonts.

There are several system libraries that PIL relies on, so installing via a package

manager is the easiest way to bring in everything:

sudo apt-get install python3-pil

•

That's it. You should be ready to go.

©Adafruit Industries Page 46 of 161

CircuitPython and Python Usage

The following section will show how to control the LED backpackfrom the board's

Python prompt / REPL. You'll walk through how to control the LED display and learn

how to use the CircuitPython module built for the display.

Firstconnect to the board's serial REPL(https://adafru.it/Awz)so you are at the

CircuitPython>>>prompt.

Initialization

First you'll need to initialize the I2C bus for your board. It's really easy, first import the

necessary modules. In this case, we'll use board and MatrixBackpack16x8 .

Then just use board.I2C() to create the I2C instance using the default SCL and

SDA pins (which will be marked on the boards pins if using a Feather or similar

Adafruit board).

Then to initialize the matrix, you just pass i2c in.

import board from adafruit_ht16k33.matrix import MatrixBackpack16x8

i2c = board.I2C() matrix = MatrixBackpack16x8(i2c)

If you bridged the address pads on the back of the display, you could pass in the

address. The addresses for the HT16K33 can range between 0x70 and 0x77

depending on which pads you have bridged, with 0x70 being used if you haven't

bridged any of them. For instance, if you bridge only the A0 pad, you would use

0x71 like this:

matrix = MatrixBackpack16x8(i2c, address=0x71)

Setting the Brightness

You can set the brightness of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/16 increments betw

een 0 and 1.0 with 1.0 being the brightest. So to set the display to half brightness, you

would use the following:

©Adafruit Industries Page 47 of 161

display.brightness = 0.5

Setting the Blink Rate

You can set the blink rate of the display, but changing it will set the brightness of the

entire display and not individual pixels. If can be adjusted in 1/4 incrementsbetween 0

and 3with 3 being the fastest blinking. So to set the display to blink at full speed, you

would use the following:

display.blink_rate = 3

Setting Individual Pixels

To set individual pixels to on, you simply treat the matrix object as a

multidimensional list and set it to 1.

matrix[0, 0] = 1 matrix[4, 4] = 1 matrix[7, 7] = 1

Filling the Entire Matrix

To fill the entire matrix, just use the fill() function and pass in either 0 or 1 depending

on whether you want all pixels off or on. For instance, if you wanted to set everything

to on, you would use:

matrix.fill(1)

Shifting the Matrix

To shift the pixels on the matrix, there are 5 functions you can use. The main function,

called shift(), is used to shift the pixels, up, down, left, right, or even diagonally. By

passing a positive number, it will shift the pixels right/up and passing a negative

number will shift them left/down. For instance:

©Adafruit Industries Page 48 of 161

You can pass True as a third parameter to loop all the pixels that get shifted off over

to the other side.

Additionally, there are a few convenience functions that will shift the pixels by one.

These can also be passed a value of True to loop the pixels.

Here's what shifting a smiley face to the right looks like:

Displaying an Image (Pillow Only)

Additionally, when using with the Raspberry Pi, you can use the Pillow library to

display an image to the Matrix. The image will need to be the same exact size as the

Matrix. In this case, it should be 16x8 pixels. As an example, you can save the image

below asmyimage.png.

Download Image

https://adafru.it/ICS

©Adafruit Industries Page 49 of 161

Then if you want to display the image calledmyimage.png, you would use something

like this:

import board from PIL import Image from adafruit_ht16k33 import matrix

matrix = matrix.MatrixBackpack16x8(board.I2C())

image = Image.open("myimage.png") matrix.image(image)

0.54" Alphanumeric Backpack

This version of the LED backpack is designed for two dual 14-segment "Alphanumeric"

displays. These 14-segment displays normally require 18 pins (4 'characters' and 14

total segments each) This backpack solves the annoyance of using 18 pins or a bunch

of chips by having an I2C constant-current matrix controller sit neatly on the back of

the PCB. The controller chip takes care of everything, drawing all the LEDs in the

background. All you have to do is write data to it using the 2-pin I2C interface.

There are three address select pins so you can select one of 8 addresses to control

up to 8 of these on a single 2-pin I2C bus (as well as whatever other I2C chips or

sensors you like). The driver chip can 'dim' the entire display from 1/16 brightness up

to full brightness in 1/16th steps. It cannot dim individual LEDs, only the entire display

at once.

©Adafruit Industries Page 50 of 161

To get you going fast, we have revised this popular board to be the same size and

pinout as before but now with twoSTEMMA QT connectors(https://adafru.it/JqB)on

either side that are compatible with theSparkFun Qwiic(https://adafru.it/Fpw)I2C

connectors. This allows you to make solderless connections between your

development board and the HT16K33 or to chain it with a wide range of other sensors

and accessories using acompatible cable(https://adafru.it/JnB).

There are two versions of this board - the STEMMA QT version shown above, and

the original header-only version shown below. Code works the same on both!

©Adafruit Industries Page 51 of 161

Pinouts

There are a number of features on the 0.54" Alphanumeric Backpack.

STEMMA QT Revision-Only Features

These features are only available on the STEMMA QT revision.

STEMMA QT Connectors

The default I2C address is 0x70.

TheSTEMMA QT connectors(https://

adafru.it/Ft4) provide a solder-free way to

connect this backpack to development

boards with STEMMA QT connectors, or to

other things, with various associated

accessories(https://adafru.it/Qgf).

©Adafruit Industries Page 52 of 161

On LED and LED Jumper

On LED - On the left side of the back of

the board is a little green LED labeled On.

This LED lights up when the board is

successfully powered.

LED jumper - To the right of the On LED is

a jumper labeled LED. If you wish to

disable the On LED, you can cut the trace

between the two pads. To enable it again,

use solder to reconnect the two pads.

Original and STEMMA QT Version Features

These features are available on both versions. There is one header pin difference

between the two, which is explained in the next section. Everything else is the same.

Header Pin Through-Hole Pads

If you prefer to use a breadboard, there are through-hole header pin pads along the

top of the board in the middle.

The default I2C address is 0x70.

©Adafruit Industries Page 53 of 161

On both versions:

VIO/VCC - This is power for the backpack.

It can be 3V-5V. To power the backpack,

give it the same power as the logic level of

your microcontroller - e.g. for a 5V

microcontroller like Arduino, use 5V.

GND - This is common ground for power

and logic.

SCL - This is the I2C clock pin. Connect it

to your microcontroller I2C clock line. This

pin is level shifted so you can use 3-5V

logic, and there's a10K pullupon this pin.

SDA - This is the I2C data pin. Connect it

to your microcontroller I2C data line. This

pin is level shifted so you can use 3-5V

logic, and there's a10K pullupon this pin.

©Adafruit Industries Page 54 of 161

On the STEMMA QT revision ONLY:

VHi - This pin allows you to provide 5V to only the 14-segment displays when

•

using a 3V device to control the backpack. If you're using a 3V device and you

want your displays to be brighter, you can maintain the 3V I2C power level, and

connect 5V to the VHi pin to make the 14-segment displays have a brighter look.

On the original version ONLY:

Vi2c - This is the I2C voltage, which sets the logic level to I2C. Connect this pin

•

to the voltage pin on your device that matches the device's logic level. For

example, if you're using a 3.3V microcontroller, connect it to 3.3V.

©Adafruit Industries Page 55 of 161

Display Pin Through-Hole Pads

These two rows of through-hole pads are

for soldering the alphanumeric LED

displays onto the backpack. See the

Assembly page(https://adafru.it/11dU) for

details on attaching the displays properly.

©Adafruit Industries Page 56 of 161

HT16K33 Matrix Driver

The chip located in the center of the back

of the backpack is the HT16K33 matrix

driver, which drives the 14-segment LED

displays.

©Adafruit Industries Page 57 of 161

Address Jumper Pins

On the back of the board are three

address jumpers, labeled A0, A1, and A2.

These jumpers allow you to chain up to 8

of these boards on the same pair of I2C

clock and data pins. To do so, you solder

the jumpers "closed" in various

combinations by connecting the two pads.

The default I2C address is 0x70. The other

address options can be calculated by

“adding” the A0/A1/A2 to the base of

0x70.

A0 sets the lowest bit with a value of 1, A1 sets the next bit with a value of 2 and A2

sets the next bit with a value of 4. The final address is 0x70 + A2 + A1 + A0 which

would be 0x77.

So for example if A2 is soldered closed and A0 is soldered closed, the address is 0x7

0 + 4 + 1 = 0x75.

If only A0 is soldered closed, the address is 0x70 + 1 = 0x71

If only A1 is soldered closed, the address is 0x70 + 2 = 0x72

If only A2 is soldered closed, the address is 0x70 + 4 = 0x74

©Adafruit Industries Page 58 of 161

The table below shows all possible addresses, and whether the pin(s) should be high

(closed) or low (open).

Assembly

Attaching the Backpack

The assembly photos below are the original version. Assembly is the same for both

the original version and the STEMMA QT version.

This assembly is the same on the STEMMA QT version of the backpack!

When you buy a pack from Adafruit, it

comes with the fully tested and assembled

backpack as well as two dual 14-segment

display in one of the colors we provide

(say, red, yellow, blue or green). You'll

need to solder the matrix onto the

backpack but it's an easy task.

Remove the parts from packaging and

place the LED matrices OVER the

silkscreen side. DO NOT PUT THE

DISPLAY ON UPSIDE DOWN OR IT WONT

WORK!! Check the image below to make

sure the 'decimal point' dots are on the

bottom, matching the silkscreen.

©Adafruit Industries Page 59 of 161

Turn the backpack over so it is sitting flat

on the matrix.

©Adafruit Industries Page 60 of 161

Solder all of the pins!

©Adafruit Industries Page 61 of 161

Clip the long pins.

©Adafruit Industries Page 62 of 161

Attaching Header

Check your work, making sure each pin is

nicely soldered, and there's no cold solder

joints or shorted pins

Prepare the header strip:

Cut the strip to length if necessary. It will

be easier to solder if you insert it into a

breadboard - long pins down

Add the Backpack:

Place the backpack board over the pins so

that the short pins poke through the

breakout pads

©Adafruit Industries Page 63 of 161

Solder all 5 pins!

That's it! now you're ready to run the firmware on your Arduino!

Arduino Wiring and Setup

Downloading the Arduino Library

We wrote a basic library to help you work with the alphanumeric backpack. The

library is written for the Arduino and will work with any Arduino as it just uses the I2C

pins. The code is very portable and can be easily adapted to any I2C-capable micro.

Begin by downloading our Adafruit LED Backpack library (https://adafru.it/aLI)and the

Adafruit GFX library(https://adafru.it/aJa) from the Arduino library manager.

Open up the Arduino library manager:

Search for theAdafruit LED Backpacklibrary and install it

©Adafruit Industries Page 64 of 161

When asked to install dependencies, click Install all.

We also have a great tutorial on Arduino library installation at:

http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use(https://

adafru.it/aYM)

You can use these with a 3.3v or 5v microcontroller. Just make sure the Vi2c pin

is the same voltage as the logic on your microcontroller.

Wiring STEMMA QT Version

Here is an example of the STEMMA QT version wired to a Metro using the STEMMA

QT connector on the backpack.

Board 5Vto backpack Vio (red wire)

Board GNDto backpack GND (black wire)

Board SCLto backpack SCL (yellow wire)

Board SDAto backpack SDA (blue wire)

©Adafruit Industries Page 65 of 161

Here is an example of the STEMMA QT version wired to a Metro using a solderless

breadboard. This example also includes how to wire up the VHi pin, which makes the

LEDs appear brighter.

Board 5Vto backpack Vio (long red wire)

Board GNDto backpack GND (black wire)

Board SCLto backpack SCL (yellow wire)

Board SDAto backpack SDA (blue wire)

Backpack VIO to backpack VHi (short red

wire)

Wiring Original Version

Connect CLK to the I2C clock - on Arduino

UNO thats Analog #5 (or SCL), on the

Leonardo it's Digital #3, on the Mega it's

digital #21

Connect DAT to the I2C data - on Arduino

UNO thats Analog #4 (or SDA), on the

Leonardo it's Digital #2, on the Mega it's

digital #20

Connect GND to common ground

Connect VCC+ to power - 5V is best but

3V will work if that's all you've got (it will

be dimmer)

Connect Vi2c to your microcontroller's

logic level (3-5V) - If you're using an

Arduino, this is almost certainly 5V. If its a

3V Arduino such as a Due, connect it to 3V

Both Vi2c and Vcc MUST be connected to

3 to 5VDC! Vcc is for the LED driver power,

Vi2c is what sets the logic level for

communication to the chip.

©Adafruit Industries Page 66 of 161

Load Demo

Restart the Arduino IDE and load up the File→Adafruit_LEDBackpack→quadalphanum

demo

Upload to your Arduino, and open up the Serial console at 9600 baud speed. You'll

see each digit light up all the segments, then the display will scroll through the 'font

table' showing every character that it knows how to display. Finally, you'll get a notice

to start typing into the serial console. Type a message and hit return, you'll see it

scroll onto the display!

©Adafruit Industries Page 67 of 161

Library Reference

For the quad displays, we have a special object that can handle ascii data for easy

printing.

You can create the object with

Adafruit_AlphaNum4 alpha4 = Adafruit_AlphaNum4();

There's no arguments or pins because the backpacks use the fixed I2C pins.

By default, the address is 0x70, but you can pass in the I2C address used when you

initialize the display with begin

alpha4.begin(0x70); // pass in the address

Next up, the segments can be turned on/off for each digit by writing the 'raw' bitmap

you want, for example, all the LEDs off on digit #3 is

alpha4.writeDigitRaw(3, 0x0);

All the segments on for digit #0 is

alpha4.writeDigitRaw(0, 0x3FFF);

This is the segment map:

©Adafruit Industries Page 68 of 161

the 16 bit digit you pass in for raw image has this mapping:

0 DP N M L K J H G2 G1 F E D C B A

The first bit isn't used, you can make it 0 or 1

To turn on just the A segment, use 0x0001

To turn on just the G1 segment, use 0x0040

ASCII data

If you're just looking to print 'text' you can use our font table, just pass in an ASCII

character!

For example, to set digit #0 to A call:

alpha4.writeDigitAscii(0, 'A')

Writing Data

Don't forget to 'write' the data to the display with

alpha4.writeDisplay();

That's what actually 'sets' the data onto the LEDs!

©Adafruit Industries Page 69 of 161

CircuitPython Wiring and Setup

It's easy to use LED AlphaNumeric Displays with CircuitPython and the Adafruit

CircuitPython HT16K33(https://adafru.it/u1E) library. This module allows you to easily

write CircuitPython code to control the display.

You can use this backpack with any CircuitPython microcontroller board.

First assemble your AlphaNumeric Display(https://adafru.it/11dU).

Wiring STEMMA QT Version

Here is an example of the STEMMA QT version wired to a Feather RP2040 using the

STEMMA QT connector on the backpack.

Board 3.3Vto backpack Vio (red wire)

Board GNDto backpack GND (black wire)

Board SCLto backpack SCL (yellow wire)

Board SDAto backpack SDA (blue wire)

Here is an example of the STEMMA QT version wired to a Feather RP2040 using a

solderless breadboard. This example also includes how to wire up the VHi pin, which

makes the LEDs appear brighter.

Board 5Vto backpack Vio (red wire

connected along the bottom of the

Feather)

Board GNDto backpack GND (black wire)

Board SCLto backpack SCL (yellow wire)

Board SDAto backpack SDA (blue wire)

Board USB to backpack VHi (red wire

connected along the top of the Feather)

Wiring Original Version

Connect the AlphaNumeric Display to your microcontroller board as shown below.

Microcontroller 3Vto AlphaNumeric

Display I2C VIN

Microcontroller 3Vto AlphaNumeric

DisplayVIN

Microcontroller GNDto AlphaNumeric

DisplayGND

Microcontroller SCLto AlphaNumeric

DisplaySCL

Microcontroller SDAto AlphaNumeric

DisplaySDA

HT16K33 Library Installation

To use with CircuitPython, you need to first install the HT16K33 library, and its

dependencies, into thelibfolder on yourCIRCUITPYdrive. Then you need to

updatecode.pywith the example script.

Thankfully, you can do this in one go. In the example below, click theDownload

Project Bundlebutton below to download the necessary libraries and thecode.pyfile

in a zip file. Extract the contents of the zip file, and copy theentirelibfolderand thec

ode.pyfile to yourCIRCUITPYdrive.

YourCIRCUITPY/libfolder should contain the following folders:

adafruit_bus_device/

•

adafruit_ht16k33/

•

# SPDX-FileCopyrightText: 2022 Kattni Rembor for Adafruit Industries # SPDX-License-Identifier: MIT

import time import board from adafruit_ht16k33 import segments

# Create the display object. # Display connected to STEMMA QT connector. display = segments.Seg14x4(board.STEMMA_I2C()) # Display connected to I2C pins. # display = segments.Seg14x4(board.I2C())

# This section displays four 0's across the display. The code shows four # different ways to use the set_digit_raw function. Each is labeled below. # 16-bit Hexadecimal number display.set_digit_raw(0, 0x2D3F) time.sleep(0.2) # 16-bit Binary number display.set_digit_raw(1, 0b0010110100111111) time.sleep(0.2) # 8-bit Binary Tuple display.set_digit_raw(2, (0b00101101, 0b00111111)) time.sleep(0.2) # 8-bit Hexadecimal List display.set_digit_raw(3, [0x2D, 0x3F]) time.sleep(0.2)

# Delay between. time.sleep(2)

# Scroll "Hello, world!" across the display. Setting the loop parameter to false allows you to # tell the marquee function to run only once. By default, marquee loops indefinitely. display.marquee("Hello, world!", loop=False)

# Delay between. time.sleep(2)

# Scroll special characters, uppercase and lowercase letters, and numbers across # the display in a loop. This section will continue to run indefinitely. display.marquee("".join(chr(character) for character in range(ord("!"), ord("z") +

1)))

Python Wiring and Setup

Wiring

It's easy to use AlphaNumeric Displays with Python and the Adafruit CircuitPython

HT16K33(https://adafru.it/u1E) library. This library allows you to easily write Python

code to control the display.

This section will cover how to wire the AlphaNumeric Display to your Raspberry Pi.

First assemble your AlphaNumeric Display.

Since there's dozens of Linux computers/boards you can use, this guide will just show

wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on

Linux to see whether your platform is supported(https://adafru.it/BSN).

Connect the AlphaNumeric Display as shown below to your Raspberry Pi.

Wiring STEMMA QT Version

Here is an example of wiring the STEMMA QT version of the backpack to a Raspberry

Pi using the STEMMA QT connector.

Pi GNDto backpack GND (black wire)

Pi 3.3Vto backpack VIO (red wire)

Pi SDAto backpack SDA (blue wire)

Pi SCLto backpack SCL (yellow wire)

Here is an example of wiring the STEMMA QT version of the backpack using a

solderless breadboard. This example also includes how to wire up the VHi pin, which

makes the LEDs appear brighter.

Wiring Original Version

Pi GNDto backpack GND (black wire)

Pi 3.3Vto backpack VIO (lower red wire)

Pi SDAto backpack SDA (blue wire)

Pi SCLto backpack SCL (yellow wire)

Pi 5V to backpack VHi (upper red wire)

Raspberry Pi 3.3Vto AlphaNumeric

Display I2C VIN

Raspberry Pi 3.3Vto AlphaNumeric

DisplayVIN

Raspberry Pi GNDto AlphaNumeric

DisplayGND

Raspberry Pi SCLto AlphaNumeric

DisplaySCL

Raspberry Pi SDAto AlphaNumeric

DisplaySDA

Setup

You'll need to install the Adafruit_Blinka library that provides the CircuitPython

support in Python. This may also require enabling I2C on your platform and verifying

you are running Python 3. Since each platform is a little different, and Linux changes

often, please visit the CircuitPython on Linux guide to get your computer ready(https:

//adafru.it/BSN)!

Python Installation of HT16K33 Library

Once that's done, from your command line run the following command:

pip3 install adafruit-circuitpython-ht16k33•

If your default Python is version 3 you may need to run 'pip' instead. Just make sure

you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

If that complains about pip3 not being installed, then run this first to install it:

sudo apt-get install python3-pip

•

Pillow Library

You also need PIL, the Python Imaging Library, to allow using text with custom fonts.

There are several system libraries that PIL relies on, so installing via a package

manager is the easiest way to bring in everything:

sudo apt-get install python3-pil

•

That's it. You should be ready to go.

CircuitPython and Python Usage

The following section will show how to control the LED backpackfrom the board's

Python prompt / REPL. You'll walk through how to control the LED display and learn

how to use the CircuitPython module built for the display.

Firstconnect to the board's serial REPL(https://adafru.it/Awz)so you are at the

CircuitPython>>>prompt.

Initialization

First you'll need to initialize the I2C bus for your board. It's really easy, first import the

necessary modules. In this case, you'll use board and Seg14x4 .

Then just use board.I2C() to create the I2C instance using the default SCL and

SDA pins (which will be marked on the boards pins if using a Feather or similar

Adafruit board).

Then to initialize the display, you just pass i2c in.

import board from adafruit_ht16k33.segments import Seg14x4

i2c = board.I2C() display = Seg14x4(i2c)

If you bridged the address pads on the back of the display, you could pass in the

address. The addresses for the HT16K33 can range between 0x70 and 0x77

depending on which pads you have bridged, with 0x70 being used if you haven't

bridged any of them. For instance, if you bridge only the A0 pad, you would use

0x71 like this:

display = Seg14x4(i2c, address=0x71)

If you intend to chain multiple displays together, you will need to alter the address of

subsequent boards by bridging the address pins in various combinations(https://

adafru.it/11eg). If you have an unsoldered board, and a board with the A0 pad solder-

bridged, you would initialise the two displays as follows.

display = Seg14x4(i2c, address=(0x70, 0x71))

To add further displays, ensure the address is different on all of them(https://adafru.it/

11eg), and initialise it the same way as above, but add more comma-separated

addresses to the address=() tuple.

Setting the Brightness

You can set the brightness of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/16 increments betw

een 0 and 1.0 with 1.0 being the brightest. So to set the display to half brightness, you

would use the following:

display.brightness = 0.5

Setting the Blink Rate

You can set the blink rate of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/4 increments betwe

en 0 and 3 with 3 being the fastest blinking. So to set the display to blink at full

speed, you would use the following:

display.blink_rate = 3

Printing Text

To print text to the display, you just use the print function. So if you want to print

ABCD, you would use the following:

display.print("ABCD")

Printing Numbers

Printing numbers is done similar to printing text, except without the quotes, though

you can still print numbers in a string as well.

display.print(1234)

Printing Hexidecimal Values

To print hexidecimal values, you use the print_hex function:

display.print_hex(0x1A2B)

Setting Individual Characters

To set individual characters, you simply treat the display object as a list and set it

tothe value that you would like.

display[0] = '1' display[1] = '2' display[2] = 'A' display[3] = 'B'

Setting Individual Segments

To set individual segments to turn on or off, you would use the set_digit_raw function

to pass the digit that you want to change and the bitmask. This can be really useful

for creating your own characters. The bitmask corresponds to the following diagram.

The highest bit is not used, so an X represents that spot to indicate that.

The bitmask is a 16-bit number that can be passed in as a single Hexidecimal,

Decimal, or binary number. It can also be passed in as a list or tuple containing 2

separate 8-bit numbers. Here are some of the ways to set the digits. All of these

different methods create a box with an X in the center:

display.set_digit_raw(0, 0x2D3F) display.set_digit_raw(1, 0b0010110100111111) display.set_digit_raw(2, (0b00101101, 0b00111111)) display.set_digit_raw(3, [0x2D, 0x3F])

Filling all Segments

To fill the entire display, just use the fill() function and pass in either 0 or 1 depending

on whether you want all segments off or on. For instance, if you wanted to set

everything to on, you would use:

display.fill(1)

Scrolling Display Manually

If you want to scroll the displayed data to the left, you can use the scroll()

function. You can pass in the number of places that you want to scroll. The right-most

digit will remain unchanged and you will need to set that manually. After scrolling, you

will need to call the show function. For example if you wanted to print an A and then

scroll it over to spaces, you would do the following.

display.print("A") display.scroll(2) display[3] = " " display.show()

Displaying an Automatic Scrolling Marquee

To make displaying long text easier, you can use the marquee function. You just pass

it the full string. Optionally, you can pass it the amount of delay between each

character:

display.marquee("This is a really long string ")

By default it is 0.25 seconds, but you can change this by providing a second

parameter. You can optionally pass False for a third parameter if you would not like

to have it loop. So if you wanted each character to display for half a second and didn't

want it to loop, you would use the following:

display.marquee('This is a really long string ', 0.5, False)

Full Example

Click Download Project Bundle below to download a full examplecode.py and

necessary libraries to run it.

# SPDX-FileCopyrightText: 2022 Kattni Rembor for Adafruit Industries # SPDX-License-Identifier: MIT

import time import board from adafruit_ht16k33 import segments

# Create the display object. # Display connected to STEMMA QT connector. display = segments.Seg14x4(board.STEMMA_I2C()) # Display connected to I2C pins. # display = segments.Seg14x4(board.I2C())

# Delay between. time.sleep(2)

1)))

0.56" 7-Segment Backpack

This version of the LED backpack is designed for these big bright 7-segment displays.

These 7-segment displays normally require 13 pins (5 'characters' and 8 total

segments each) This backpack solves the annoyance of using 13 pins or a bunch of

chips by having an I2C constant-current matrix controller sit neatly on the back of the

PCB. The controller chip takes care of everything, drawing all the LEDs in the

background. All you have to do is write data to it using the 2-pin I2C interface. There

are three address select pins so you can select one of 8 addresses to control up to 8

of these on a single 2-pin I2C bus (as well as whatever other I2C chips or sensors you

like). The driver chip can 'dim' the entire display from 1/16 brightness up to full

brightness in 1/16th steps. It cannot dim individual LEDs, only the entire display at

once.

To get you going fast, we have revised this popular board to be the same size and

pinout as before but now with two STEMMA QT connectors(https://adafru.it/JqB)on

either side that are compatible with theSparkFun Qwiic(https://adafru.it/Fpw)I2C

connectors. This allows you to make solderless connections between your

development board and the HT16K33 or to chain it with a wide range of other sensors

and accessories using acompatible cable(https://adafru.it/JnB).

Assembly and Arduino Wiring

For the STEMMA QT version, you can solder the headers on, or you can simply use a

STEMMA QT cable!

Backpack + (VCC) to microcontroller 5V (if

using a board with 5V logic, otherwise use

3V for boards with 3V logic) (red wire)

Backpack - (GND) to microcontroller GND

(black wire)

Backpack D (SDA) to microcontroller SDA

(blue wire)

Backpack C (SCL) to microcontroller SCL

(yellow wire)

To assemble the LED backpack, follow along below.

Soldering the 7-segment display is the same for the STEMMA QT version and the

original version.

When you buy a pack from Adafruit, it

comes with the fully tested and assembled

backpack as well as a 7-segment display in

one of the colors we provide (say, red,

yellow, blue or green). You'll need to

solder the matrix onto the backpack but

it's an easy task.

Remove the parts from packaging and

place the LED matrix OVER the silkscreen

side.DO NOT PUT THE DISPLAY ON

UPSIDE DOWN OR IT WONT WORK!!

Check the image below to make sure the

'decimal point' dots are on the bottom,

matching the silkscreen.

Turn the backpack over so it is sitting flat

on the matrix.

Solder all 14 pins.

Clip the long pins.

Now you're ready to wire it up to a

microcontroller. We'll assume you want to

use a 4pin header. You can also of course

solder wires directly. Place a 4-pin piece of

header with the LONG pins down into the

breadboard.

Place the soldered backpack on top of the

header and Solder 'em!

That's it! now you're ready to run the firmware!

Arduino Setup

You can use these with a 3.3v or 5v microcontroller. Just connect the VCC+ pin is

the same voltage as the logic on your microcontroller.

Seven-Segment Backpack Firmware

We wrote a basic library to help you work with the 7-segment backpack. The library is

written for the Arduino and will work with any Arduino as it just uses the I2C pins. The

code is very portable and can be easily adapted to any I2C-capable micro.

Wiring to the matrix is really easy

Connect CLK to the I2C clock - on Arduino UNO thats Analog #5 (or SCL), on the

•

Leonardo it's Digital #3, on the Mega it's digital #21

Connect DAT to the I2C data - on Arduino UNO thats Analog #4 (or SDA), on the

•

Leonardo it's Digital #2, on the Mega it's digital #20

Connect GND to common ground

•

Connect VCC+ to power - 5V is best but 3V also seems to work for 3V

•

microcontrollers.

Next, download theAdafruit LED Backpacklibrary and theAdafruit GFXlibrary from

the Arduino library manager.

Open up the Arduino library manager:

Search for theAdafruit LED Backpacklibrary and install it

Search for theAdafruit GFXlibrary and install it

If using an earlier version of the Arduino IDE (prior to 1.8.10), also locate and install Ad

afruit_BusIO (newer versions will install this dependency automatically).

Once you've restarted you should be able to select the

File→Examples→Adafruit_LEDBackpack→sevenseg example sketch. Upload it to your

Arduino as usual. You should see a basic test program that goes through a bunch of

different routines.

We also have a great tutorial on Arduino library installation at:

http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use(https://

adafru.it/aYM)

Once you're happy that the matrix works, you can write your own sketches.

There's a few ways you can draw to the display. The easiest is to just call print - just

like you do with Serial

print(variable,HEX) - this will print a hexidecimal number, from 0000 up to FFFF

•

print(variable,DEC) or print(variable) - this will print a decimal integer, from 0000

•

up to 9999

If you need more control, you can call writeDigitNum(location, number) - this will write

the number (0-9) to a single location. Location #0 is all the way to the left, location #2

is the colon dots so you probably want to skip it, location #4 is all the way to the right.

If you want a decimal point, call writeDigitNum(location, number, true) which will paint

the decimal point. To draw the colon, usedrawColon(true or false)

If you wanteven more control, you can call writeDigitRaw(location,bitmask) to draw a

raw 8-bit mask (as stored in a uint8_t) to that location.

All the drawing routines only change the display memory kept by the Arduino. Don't

forget to call writeDisplay() after drawing to 'save' the memory out to the matrix via

I2C.

There are also a few small routines that are special to the backpack:

setBrightness(brightness)- will let you change the overall brightness of the entire

•

display. 0 is least bright, 15 is brightest and is what is initialized by the display

when you start

blinkRate(rate) - You can blink the entire display. 0 is no blinking. 1, 2 or 3 is for

•

display blinking.

CircuitPython Wiring and Setup

Wiring

It's easy to use LED 7-Segment Displays with CircuitPython and the Adafruit

CircuitPython HT16K33(https://adafru.it/u1E) library. This module allows you to easily

write CircuitPython code to control the display.

You can use this sensor with any CircuitPython microcontroller board.

We'll cover how to wire the 7-Segment Display to your CircuitPython microcontroller

board. First assemble your 7-Segment Display.

Connect the 7-Segment Display to your microcontroller board as shown below.

Microcontroller 3Vto 7-Segment Display

VIN (red wire)

Microcontroller GNDto 7-Segment Display

GND (black wire)

Microcontroller SCLto 7-Segment Display

SCL (yellow wire)

Microcontroller SDAto 7-Segment Display

SDA (blue wire)

Download Fritzing Object

https://adafru.it/ICk

Library Setup

To use the LED backpackwith yourAdafruit CircuitPython(https://adafru.it/BlM)board

you'll need to install theAdafruit_CircuitPython_HT16K33(https://adafru.it/u1E) library

on your board.

First make sure you are running thelatest version of Adafruit CircuitPython(https://

adafru.it/tBa)for your board. Next you'll need to install the necessary librariesto use

the hardware--read below and carefully follow the referenced steps to find and install

these libraries from Adafruit's CircuitPython library bundle(https://adafru.it/zdx).

Bundle Install

For express boards that have extra flash storage, like the Feather/Metro M0 express

and Circuit Playground express, you can easily install the necessary libraries with Ada

fruit's CircuitPython bundle(https://adafru.it/zdx). This is an all-in-one package that

includes the necessary libraries to use the LED backpack display with CircuitPython.

For details on installing the bundle, read about CircuitPython Libraries(https://

adafru.it/ABU).

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/

Metro M0 basic you'll need to manually install the necessary libraries(https://adafru.it/

ABU) from the bundle:

adafruit_ht16k33

•

adafruit_bus_device

•

If your board supports USB mass storage, like the M0-based boards, then simply drag

the files to the board's file system.Note on boards without external SPI flash, like a

Feather M0 or Trinket/Gemma M0, you might run into issues on Mac OSX with hidden

files taking up too much space when drag and drop copying,see this page for a

workaround(https://adafru.it/u1d).

Before continuing make sure your board's lib folder or root filesystem has at least

theadafruit_ht16k33 andadafruit_bus_devicefolders/modules copied over.

Python Wiring and Setup

Wiring

It's easy to use 7-Segment Displays with Python and the Adafruit CircuitPython

HT16K33(https://adafru.it/u1E) library. This library allows you to easily write Python

code to control the display.

We'll cover how to wire the 7-Segment Display to your Raspberry Pi. First assemble

your 7-Segment Display.

Since there's dozens of Linux computers/boards you can use we will show wiring for

Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to

see whether your platform is supported(https://adafru.it/BSN).

Connect the 7-Segment Display as shown below to your Raspberry Pi.

Raspberry Pi 3.3Vto 7-Segment Display

VIN (red wire)

Raspberry Pi GNDto 7-Segment Display

GND (black wire)

Raspberry Pi SCLto 7-Segment Display

SCL (yellow wire)

Raspberry Pi SDAto 7-Segment Display

SDA (blue wire)

Download Fritzing Object

https://adafru.it/ICl

Setup

You'll need to install the Adafruit_Blinka library that provides the CircuitPython

support in Python. This may also require enabling I2C on your platform and verifying

you are running Python 3. Since each platform is a little different, and Linux changes

often, please visit the CircuitPython on Linux guide to get your computer ready(https:

//adafru.it/BSN)!

Python Installation of HT16K33 Library

Once that's done, from your command line run the following command:

pip3 install adafruit-circuitpython-ht16k33

•

If your default Python is version 3 you may need to run 'pip' instead. Just make sure

you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

If that complains about pip3 not being installed, then run this first to install it:

sudo apt-get install python3-pip

•

Pillow Library

We also need PIL, the Python Imaging Library, to allow using text with custom fonts.

There are several system libraries that PIL relies on, so installing via a package

manager is the easiest way to bring in everything:

sudo apt-get install python3-pil

•

That's it. You should be ready to go.

CircuitPython and Python Usage

The following section will show how to control the LED backpackfrom the board's

Python prompt / REPL. You'll walk through how to control the LED display and learn

how to use the CircuitPython module built for the display.

Firstconnect to the board's serial REPL(https://adafru.it/Awz)so you are at the

CircuitPython>>>prompt.

Initialization

First you'll need to initialize the I2C bus for your board. It's really easy, first import the

necessary modules. In this case, we'll use board and Seg7x4 .

Then just use board.I2C() to create the I2C instance using the default SCL and

SDA pins (which will be marked on the boards pins if using a Feather or similar

Adafruit board).

Then to initialize the display, you just pass i2c in.

import board from adafruit_ht16k33.segments import Seg7x4

i2c = board.I2C() display = Seg7x4(i2c)

If you bridged the address pads on the back of the display, you could pass in the

address. The addresses for the HT16K33 can range between 0x70 and 0x77

depending on which pads you have bridged, with 0x70 being used if you haven't

bridged any of them. For instance, if you bridge only the A0 pad, you would use

0x71 like this:

display = Seg7x4(i2c, address=0x71)

Setting the Brightness

You can set the brightness of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/16 increments betw

een 0 and 1.0 with 1.0 being the brightest. So to set the display to half brightness, you

would use the following:

display.brightness = 0.5

Setting the Blink Rate

You can set the blink rate of the display, but changing it will set the brightness of the

entire display and not individual segments. If can be adjusted in 1/4 increments betwe

en 0 and 3 with 3 being the fastest blinking. So to set the display to blink at full

speed, you would use the following:

display.blink_rate = 3

Printing Text

To print text to the display, you just use the print function. For the 7-segment display,

valid characters are 0-9, letters A-F, a period, and a hyphen. So if we want to print

ABCD, we would use the following:

display.print("ABCD")

Printing Numbers

Printing numbers is done similar to printing text, except without the quotes, though

you can still print numbers in a string as well.

display.print(1234)

Printing Hexidecimal Values

To print hexidecimal values, you use the print_hex function:

display.print_hex(0x1A2B)

Setting Individual Characters

To set individual characters, you simply treat the display object as a list and set it

tothe value that you would like.

display[0] = '1' display[1] = '2' display[2] = 'A' display[3] = 'B'

Setting Individual Segments

To set individual segments to turn on or off, you would use the set_digit_raw function

to pass the digit that you want to change and the bitmask. This can be really useful

for creating your own characters. The bitmask corresponds to the following diagram:

The bitmask is a single 8-bit number that can be passed in as a single Hexidecimal,

Decimal, or binary number. This will use a couple different methods to display

8.8.EE :

display.set_digit_raw(0, 0xFF) display.set_digit_raw(1, 0b11111111) display.set_digit_raw(2, 0x79) display.set_digit_raw(3, 0b01111001)

Filling all Segments

To fill the entire display, just use the fill() function and pass in either 0 or 1 depending

on whether you want all segments off or on. For instance, if you wanted to set

everything to on, you would use:

display.fill(1)

Scrolling Display Manually

If you want to scroll the displayed data to the left, you can use the scroll()

function. You can pass in the number of places that you want to scroll. The right-most

digit will remain unchanged and you will need to set that manually. After scrolling, you

will need to call the show function. For example if you wanted to print an A and then

scroll it over to spaces, you would do the following.

display.print("A") display.scroll(2) display[3] = " " display.show()

Displaying the Colon

There are a couple of different ways to display a colon on the 7-segment display. The

first and easiest way is to use the print function:

display.print("12:30")

The other way to control it is to access the colon with the colon property and set it to

True or False :

display.colon = False

Displaying an Automatic Scrolling Marquee

To make displaying long text easier, we've added a marquee function. You just pass it

the full string. Optionally, you can pass it the amount of delay between each

character. This may be useful for displaying an IP address, a phone number, or other

numeric data:

display.marquee('192.168.100.102... ')

By default it is 0.25 seconds, but you can change this by providing a second

parameter. You can optionally pass False for a third parameter if you would not like

to have it loop. So if you wanted each character to display for half a second and didn't

want it to loop, you would use the following:

display.marquee('192.168.100.102... ', 0.5, False)

1.2" 7-segment Backpack

These backpacks drive the massive 1.2" 7-segment modules. With 2 leds per segment

these make a gorgeous and impressive display. The 7-segment displays normally

require 16 pins to drive. This backpack uses an I2C constant-current matrix controller

on the back of the PCB, so you only need 2 pins to drive it!

The controller chip takes care of multiplexing all the LEDs in the background. All you

have to do is write data to it using the 2-pin I2C interface. There are three address

select pins so you can select one of 8 addresses to control up to 8 of these on a

single 2-pin I2C bus (as well as whatever other I2C chips or sensors you like). The

driver chip can 'dim' the entire display from 1/16 brightness up to full brightness in

1/16th steps. It cannot dim individual LEDs, only the entire display at once.

Assembly

When you buy a pack from Adafruit, it

comes with the fully tested and assembled

backpack as well as a 7-segment display in

one of the colors we provide (say, red,

yellow, blue or green). You'll need to

solder the matrix onto the backpack but its

an easy task.

Remove the parts from packaging and

place the LED matrix OVER the silkscreen

side. DO NOT PUT THE DISPLAY ON

UPSIDE DOWN OR IT WONT WORK!!

Check the image below to make sure the

'decimal point' dots are in the same

location as the ones on the silkscreen.

Turn the backpack over so its sitting flat on

the matrix and ready to solder.

Adafruit LED Backpacks User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual