Overview

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When you’re studying something that needs a lot of memorization, like learning a language, prepping for a tough biology exam, or mastering all those pesky built-in Python functions, it’s hard to beat a good old deck of flashcards. It’s the tried and true method of getting tough subjects to stick to your grey matter - especially when you’re on a deadline, and you’ve really got to get this stuff down or you are going to flunk most heinously tomorrow, dude!

But like many old fashioned methods, flashcards can be kind of a pain! You have to spend ages writing them all out on paper, and then somebody knocks them off the table and one goes under the fridge, and then your buddy asks to borrow them but you’re not finished and you’re not going to make him a whole other deck, are you kidding, and now the edges have gotten all bent so they don’t shuffle well any more, and then once you’ve finally gotten everything memorized there’s nothing to do but toss them all out and get started on the next deck. The results may be good, but the process? Frustrating.

Enter the MagTag!

projects_IMG_2910_2.jpg

With CircuitPython, you can type out your flashcards in JSON, and you’ll never be stuck writing and shuffling huge decks of index cards again. You can sort them by chapters, support lots of different international fonts, even share them with your slacker buddy with a simple copy-paste. Maybe not the most old-fashioned anymore, but it’s e-paper, so we’re pretty sure it still counts.

Thanks to Unicode font support in CircuitPython, you can quickly and easily make text for any language using free fonts!

This guide uses the e-paper and other hardware features of the MagTag, but note that it does not use any of the ESP32-S2 networking capabilities (WIFI, etc). Setting up WIFI is included in the installation process for completeness, but the final project will not connect to the internet, so you can skip those steps if you want! Just install Circuitpython and the libraries, and don't worry about secrets.py or the internet tests. If you'd specifically like to do a connected IoT project, we've got lots of other guides to do that - check out the full list Magtag tutorials for ideas!

Parts

The MagTag starter kit comes with a battery and some magnets included. You'll also need to grab a USB C cable separately, if you don't have one:

MagTag dev board with enclosure pieces, four magnet feet, and lipoly battery
The Adafruit MagTag combines the new ESP32-S2 wireless module and a 2.9" grayscale E-Ink display to make a low-power IoT display that can show data on its screen...
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USB Type A to Type C Cable - approx 1 meter / 3 ft long
As technology changes and adapts, so does Adafruit. This  USB Type A to Type C cable will help you with the transition to USB C, even if you're still...
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Alternatively, you can get the parts individually, if you'd like to swap out the battery or omit the magnets.

Angled shot of Adafruit MagTag development board with ESP32-S2 and E-Ink display.
The Adafruit MagTag combines the new ESP32-S2 wireless module and a 2.9" grayscale E-Ink display to make a low-power IoT display that can show data on its screen even when power...
Out of Stock
Out of Stock
Lithium Ion Polymer Battery 3.7v 420mAh with JST 2-PH connector and short cable
Lithium-ion polymer (also known as 'lipo' or 'lipoly') batteries are thin, light, and powerful. The output ranges from 4.2V when completely charged to 3.7V. This...
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Angled shot of four magnet feet.
Got a glorious RGB Matrix project you want to mount and display in your workspace or home? If you have one of the matrix panels listed below, you'll need a pack of these...
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Install CircuitPython

CircuitPython is a derivative of MicroPython designed to simplify experimentation and education on low-cost microcontrollers. It makes it easier than ever to get prototyping by requiring no upfront desktop software downloads. Simply copy and edit files on the CIRCUITPY drive to iterate.

Set Up CircuitPython

Follow the steps to get CircuitPython installed on your MagTag.

Click the link above and download the latest .BIN and .UF2 file

(depending on how you program the ESP32S2 board you may need one or the other, might as well get both)

Download and save it to your desktop (or wherever is handy).

Plug your MagTag into your computer using a known-good USB cable.

A lot of people end up using charge-only USB cables and it is very frustrating! So make sure you have a USB cable you know is good for data sync.

Option 1 - Load with UF2 Bootloader

This is by far the easiest way to load CircuitPython. However it requires your board has the UF2 bootloader installed. Some early boards do not (we hadn't written UF2 yet!) - in which case you can load using the built in ROM bootloader.

Still, try this first!

Try Launching UF2 Bootloader

Loading CircuitPython by drag-n-drop UF2 bootloader is the easier way and we recommend it. If you have a MagTag where the front of the board is black, your MagTag came with UF2 already on it.

Launch UF2 by double-clicking the Reset button (the one next to the USB C port). You may have to try a few times to get the timing right.

If the UF2 bootloader is installed, you will see a new disk drive appear called MAGTAGBOOT

Copy the UF2 file you downloaded at the first step of this tutorial onto the MAGTAGBOOT drive

If you're using Windows and you get an error at the end of the file copy that says Error from the file copy, Error 0x800701B1: A device which does not exist was specified. You can ignore this error, the bootloader sometimes disconnects without telling Windows, the install completed just fine and you can continue. If its really annoying, you can also upgrade the bootloader (the latest version of the UF2 bootloader fixes this warning)

Your board should auto-reset into CircuitPython, or you may need to press reset. A CIRCUITPY drive will appear. You're done! Go to the next pages.

Option 2 - Use esptool to load BIN file

If you have an original MagTag with while soldermask on the front, we didn't have UF2 written for the ESP32S2 yet so it will not come with the UF2 bootloader.

You can upload with esptool to the ROM (hardware) bootloader instead!

Follow the initial steps found in the Run esptool and check connection section of the ROM Bootloader page to verify your environment is set up, your board is successfully connected, and which port it's using.

In the final command to write a binary file to the board, replace the port with your port, and replace "firmware.bin" with the the file you downloaded above.

The output should look something like the output in the image.

Press reset to exit the bootloader.

Your CIRCUITPY drive should appear!

You're all set! Go to the next pages.

Option 3 - Use Chrome Browser To Upload BIN file

If for some reason you cannot get esptool to run, you can always try using the Chrome-browser version of esptool we have written. This is handy if you don't have Python on your computer, or something is really weird with your setup that makes esptool not run (which happens sometimes and isn't worth debugging!) You can follow along on the Web Serial ESPTool page and either load the UF2 bootloader and then come back to Option 1 on this page, or you can download the CircuitPython BIN file directly using the tool in the same manner as the bootloader.

CircuitPython Internet Test

One of the great things about the ESP32 is the built-in WiFi capabilities. This page covers the basics of getting connected using CircuitPython.

The first thing you need to do is update your code.py to the following. 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 code.py file to your CIRCUITPY drive.

Download Project Bundle
Copy Code 
# SPDX-FileCopyrightText: 2020 Brent Rubell for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import ipaddress
import ssl
import wifi
import socketpool
import adafruit_requests

# URLs to fetch from
TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
JSON_QUOTES_URL = "https://www.adafruit.com/api/quotes.php"
JSON_STARS_URL = "https://api.github.com/repos/adafruit/circuitpython"

# Get wifi details and more from a secrets.py file
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

print("ESP32-S2 WebClient Test")

print("My MAC addr:", [hex(i) for i in wifi.radio.mac_address])

print("Available WiFi networks:")
for network in wifi.radio.start_scanning_networks():
    print("\t%s\t\tRSSI: %d\tChannel: %d" % (str(network.ssid, "utf-8"),
            network.rssi, network.channel))
wifi.radio.stop_scanning_networks()

print("Connecting to %s"%secrets["ssid"])
wifi.radio.connect(secrets["ssid"], secrets["password"])
print("Connected to %s!"%secrets["ssid"])
print("My IP address is", wifi.radio.ipv4_address)

ipv4 = ipaddress.ip_address("8.8.4.4")
print("Ping google.com: %f ms" % (wifi.radio.ping(ipv4)*1000))

pool = socketpool.SocketPool(wifi.radio)
requests = adafruit_requests.Session(pool, ssl.create_default_context())

print("Fetching text from", TEXT_URL)
response = requests.get(TEXT_URL)
print("-" * 40)
print(response.text)
print("-" * 40)

print("Fetching json from", JSON_QUOTES_URL)
response = requests.get(JSON_QUOTES_URL)
print("-" * 40)
print(response.json())
print("-" * 40)

print()

print("Fetching and parsing json from", JSON_STARS_URL)
response = requests.get(JSON_STARS_URL)
print("-" * 40)
print("CircuitPython GitHub Stars", response.json()["stargazers_count"])
print("-" * 40)

print("done")
View on GitHub

Your CIRCUITPY drive should resemble the following.

CIRCUITPY

To get connected, the next thing you need to do is update the secrets.py file.

Secrets File

We expect people to share tons of projects as they build CircuitPython WiFi widgets. What we want to avoid is people accidentally sharing their passwords or secret tokens and API keys. So, we designed all our examples to use a secrets.py file, that is on your CIRCUITPY drive, to hold secret/private/custom data. That way you can share your main project without worrying about accidentally sharing private stuff.

The initial secrets.py file on your CIRCUITPY drive should look like this:

Download Project Bundle
Copy Code 
# SPDX-FileCopyrightText: 2020 Adafruit Industries
#
# SPDX-License-Identifier: Unlicense

# This file is where you keep secret settings, passwords, and tokens!
# If you put them in the code you risk committing that info or sharing it

secrets = {
    'ssid' : 'home_wifi_network',
    'password' : 'wifi_password',
    'aio_username' : 'my_adafruit_io_username',
    'aio_key' : 'my_adafruit_io_key',
    'timezone' : "America/New_York", # http://worldtimeapi.org/timezones
    }
View on GitHub

Inside is a Python dictionary named secrets with a line for each entry. Each entry has an entry name (say 'ssid') and then a colon to separate it from the entry key ('home_wifi_network') and finally a comma (,).

At a minimum you'll need to adjust the ssid and password for your local WiFi setup so do that now!

As you make projects you may need more tokens and keys, just add them one line at a time. See for example other tokens such as one for accessing GitHub or the Hackaday API. Other non-secret data like your timezone can also go here, just cause its called secrets doesn't mean you can't have general customization data in there!

For the correct time zone string, look at http://worldtimeapi.org/timezones and remember that if your city is not listed, look for a city in the same time zone, for example Boston, New York, Philadelphia, Washington DC, and Miami are all on the same time as New York.

Of course, don't share your secrets.py - keep that out of GitHub, Discord or other project-sharing sites.

Don't share your secrets.py file, it has your passwords and API keys in it!

If you connect to the serial console, you should see something like the following:

adafruit_products_1__screen__Users_brentrubell__screen_.png

In order, the example code...

Checks the ESP32's MAC address.

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print("My MAC addr:", [hex(i) for i in wifi.radio.mac_address])

Performs a scan of all access points and prints out the access point's name (SSID), signal strength (RSSI), and channel.

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print("Avaliable WiFi networks:")
for network in wifi.radio.start_scanning_networks():
    print("\t%s\t\tRSSI: %d\tChannel: %d" % (str(network.ssid, "utf-8"),
            network.rssi, network.channel))
wifi.radio.stop_scanning_networks()

Connects to the access point you defined in the secrets.py file, prints out its local IP address, and attempts to ping google.com to check its network connectivity. 

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print("Connecting to %s"%secrets["ssid"])
wifi.radio.connect(secrets["ssid"], secrets["password"])
print(print("Connected to %s!"%secrets["ssid"]))
print("My IP address is", wifi.radio.ipv4_address)

ipv4 = ipaddress.ip_address("8.8.4.4")
print("Ping google.com: %f ms" % wifi.radio.ping(ipv4))

The code creates a socketpool using the wifi radio's available sockets. This is performed so we don't need to re-use sockets. Then, it initializes a a new instance of the requests interface - which makes getting data from the internet really really easy.

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pool = socketpool.SocketPool(wifi.radio)
requests = adafruit_requests.Session(pool, ssl.create_default_context())

To read in plain-text from a web URL, call requests.get - you may pass in either a http, or a https url for SSL connectivity. 

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print("Fetching text from", TEXT_URL)
response = requests.get(TEXT_URL)
print("-" * 40)
print(response.text)
print("-" * 40)

Requests can also display a JSON-formatted response from a web URL using a call to requests.get. 

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print("Fetching json from", JSON_QUOTES_URL)
response = requests.get(JSON_QUOTES_URL)
print("-" * 40)
print(response.json())
print("-" * 40)

Finally, you can fetch and parse a JSON URL using requests.get. This code snippet obtains the stargazers_count field from a call to the GitHub API.

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print("Fetching and parsing json from", JSON_STARS_URL)
response = requests.get(JSON_STARS_URL)
print("-" * 40)
print("CircuitPython GitHub Stars", response.json()["stargazers_count"])
print("-" * 40)

OK you now have your ESP32 board set up with a proper secrets.py file and can connect over the Internet. If not, check that your secrets.py file has the right ssid and password and retrace your steps until you get the Internet connectivity working!

Getting The Date & Time

A very common need for projects is to know the current date and time. Especially when you want to deep sleep until an event, or you want to change your display based on what day, time, date, etc. it is

Determining the correct local time is really really hard. There are various time zones, Daylight Savings dates, leap seconds, etc. Trying to get NTP time and then back-calculating what the local time is, is extraordinarily hard on a microcontroller just isn't worth the effort and it will get out of sync as laws change anyways.

For that reason, we have the free adafruit.io time service. Free for anyone with a free adafruit.io account. You do need an account because we have to keep accidentally mis-programmed-board from overwhelming adafruit.io and lock them out temporarily. Again, it's free!

There are other services like WorldTimeAPI, but we don't use those for our guides because they are nice people and we don't want to accidentally overload their site. Also, there's a chance it may eventually go down or also require an account.

Step 1) Make an Adafruit account

It's free! Visit https://accounts.adafruit.com/ to register and make an account if you do not already have one

Step 2) Sign into Adafruit IO

Head over to io.adafruit.com and click Sign In to log into IO using your Adafruit account. It's free and fast to join.

Step 3) Get your Adafruit IO Key

Click on My Key in the top bar

adafruit_products_image.png

You will get a popup with your Username and Key (In this screenshot, we've covered it with red blocks)

adafruit_products_image.png

Go to your secrets.py file on your CIRCUITPY drive and add three lines for aio_username, aio_key and timezone so you get something like the following:

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# This file is where you keep secret settings, passwords, and tokens!
# If you put them in the code you risk committing that info or sharing it

secrets = {
    'ssid' : 'home_wifi_network',
    'password' : 'wifi_password',
    'aio_username' : 'my_adafruit_io_username',
    'aio_key' : 'my_adafruit_io_key',
    'timezone' : "America/New_York", # http://worldtimeapi.org/timezones
    }

The timezone is optional, if you don't have that entry, adafruit.io will guess your timezone based on geographic IP address lookup. You can visit http://worldtimeapi.org/timezones to see all the time zones available (even though we do not use Worldtime for time-keeping, we do use the same time zone table).

Step 4) Upload Test Python Code

This code is like the Internet Test code from before, but this time it will connect to adafruit.io and get the local time

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import ipaddress
import ssl
import wifi
import socketpool
import adafruit_requests
import secrets


TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
JSON_QUOTES_URL = "https://www.adafruit.com/api/quotes.php"
JSON_STARS_URL = "https://api.github.com/repos/adafruit/circuitpython"

# Get wifi details and more from a secrets.py file
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

# Get our username, key and desired timezone
aio_username = secrets["aio_username"]
aio_key = secrets["aio_key"]
location = secrets.get("timezone", None)
TIME_URL = "https://io.adafruit.com/api/v2/%s/integrations/time/strftime?x-aio-key=%s&tz=%s" % (aio_username, aio_key, location)
TIME_URL += "&fmt=%25Y-%25m-%25d+%25H%3A%25M%3A%25S.%25L+%25j+%25u+%25z+%25Z"

print("ESP32-S2 Adafruit IO Time test")

print("My MAC addr:", [hex(i) for i in wifi.radio.mac_address])

print("Available WiFi networks:")
for network in wifi.radio.start_scanning_networks():
    print("\t%s\t\tRSSI: %d\tChannel: %d" % (str(network.ssid, "utf-8"),
            network.rssi, network.channel))
wifi.radio.stop_scanning_networks()

print("Connecting to %s"%secrets["ssid"])
wifi.radio.connect(secrets["ssid"], secrets["password"])
print("Connected to %s!"%secrets["ssid"])
print("My IP address is", wifi.radio.ipv4_address)

ipv4 = ipaddress.ip_address("8.8.4.4")
print("Ping google.com: %f ms" % wifi.radio.ping(ipv4))

pool = socketpool.SocketPool(wifi.radio)
requests = adafruit_requests.Session(pool, ssl.create_default_context())

print("Fetching text from", TIME_URL)
response = requests.get(TIME_URL)
print("-" * 40)
print(response.text)
print("-" * 40)

After running this, you will see something like the below text. We have blocked out the part with the secret username and key data!

adafruit_products_image.png

Note at the end you will get the date, time, and your timezone! If so, you have correctly configured your secrets.py and can continue to the next steps!

Simple Flashcards

We’ll start off by working through a quick app that just does the very basics we need to study. It’ll load up some cards out of a JSON file, shuffle them, and go through them one at a time as you press the D button on the MagTag. In the next section, we’ll add some fancier features, like sorting your cards into categories, and letting you pick which ones you’d like to study per session.

In this code, we’ll be using a PCF font for international character sets. PCF fonts offer a little extra efficiency compared to raw BDF (bitmap) fonts, so they’re easier to fit on CircuitPython drives. We’ll be using one today for the Japanese Hiragana and Katakana characters used in this deck.

Installing Project Code

To use with CircuitPython, you need to first install a few libraries, into the lib folder on your CIRCUITPY drive. Then you need to update code.py with the example script.

Thankfully, we 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, open the directory MagTag_Flashcards/basic/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your CIRCUITPY drive.

Your CIRCUITPY drive should now look similar to the following image:

CIRCUITPY
Download Project Bundle
Copy Code 
# SPDX-FileCopyrightText: 2021 Anne Barela for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import time
import json
import terminalio
import digitalio
import random
from adafruit_magtag.magtag import MagTag

# Set up the magtag
print("Magtag Basic Flashcards")
magtag = MagTag()

# Import cards
cards = {}
with open("deck.json") as fp:
    cards = json.load(fp)

# Create a text area
magtag.add_text(
    text_font="yasashi20.pcf",
    text_position=(
        magtag.graphics.display.width // 2,
        magtag.graphics.display.height // 2,
    ),
    line_spacing=0.85,
    text_anchor_point=(0.5, 0.5),
)

# Set up buttons
cur_btn = False
prev_btn = False

while True:
    # Shuffle the deck
    cards = sorted(cards, key=lambda _: random.random())
    for card in cards:

        # Show the first side and wait for the D button
        text = ''.join(magtag.wrap_nicely(card[0], 20))
        magtag.set_text(text)
        while True:
            cur_btn = magtag.peripherals.button_d_pressed
            if cur_btn and not prev_btn:
                print("Show Result")
                time.sleep(0.1)
                break
            prev_btn = cur_btn

        # Show the second side and wait for the D button
        text = '\n'.join(magtag.wrap_nicely(card[1], 11))
        text += '\n'
        text += '\n'.join(magtag.wrap_nicely(card[2], 20))
        print(text)
        magtag.set_text(text)
        while True:
            cur_btn = magtag.peripherals.button_d_pressed
            if cur_btn and not prev_btn:
                print("Next Card")
                time.sleep(0.1)
                break
            prev_btn = cur_btn
View on GitHub

Example Deck

In addition, here's an example "deck" of cards, written in JSON. In case you've never used JSON before, it stands for JavaScript Object Notation: it's a format of writing data (like arrays and key-value pairs) that was originally derived from Javascript but is now commonly used across many different programming languages. In this example deck file, we create a list of lists, using square brackets [] to enclose the lists and commas , to separate list elements.

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[
    ["Monday","げつ　ようび","Getsu yōbi"],
    ["Tuesday","か　ようび","Ka yōbi"],
    ["Wednesday","すい　ようび","Sui yōbi"],
    ["Thursday","もく　ようび","Moku yōbi"],
    ["Friday","きん　ようび","Kin yōbi"],
    ["Saturday","ど　ようび","Do yōbi"],
    ["Sunday","にち　ようび","Nichi yōbi"]
]

This particular example is written for studying Japanese, but it should work fine for any topic you want - Spanish, geography, code reference, obscure Star Trek trivia, whatever. Just make sure to tweak the text-displaying parts of the code if you add or remove “sections” of the card structure.

How does it work?

Let's walk through this code step by step. First, we import all the required libraries, and create an object for the magtag that contains all the library features, like detecting button presses. We'll also tell the Serial Port we've started up the program.

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import time
import json
import terminalio
import digitalio
import random
from adafruit_magtag.magtag import MagTag

# Set up the magtag
print("Magtag Basic Flashcards")
magtag = MagTag()

Then, we use the json library to open our deck file, and interpret the JSON syntax into a list-of-lists that we can use in Python. 

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# Import cards
cards = {}
with open("deck.json") as fp:
    cards = json.load(fp)

As the last part of our setup, we create a text object to hold the sides of our flashcard. This uses the Yasashi 20 point PCF font, which contains both english and Japanese Hira and Katakana characters (no Kanji, though, sadly - that's a bit too much for the size of the Magtag's memory).

We'll put it right in the center of the screen.

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# Create a text area
magtag.add_text(
    text_font="yasashi20.pcf",
    text_position=(
        magtag.graphics.display.width // 2,
        magtag.graphics.display.height // 2,
    ),
    line_spacing=0.85,
    text_anchor_point=(0.5, 0.5),
)

To actually change the sides of the card, and to move to the next card, we'll need to detect when a magtag button is pressed.

The magtag library contains the attribute magtag.peripherals.button_d_pressed, which will tell us whether the D button is currently up or down. But this value by itself isn't able to detect when the button is pressed. To do that, we'll create a couple of memory variables:

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cur_btn = False
prev_btn = False

Whenever we want to wait for a button press, we'll enter a short while loop, and do nothing until we see the button change from an "up" state to a "down" state.

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while True:
    cur_btn = magtag.peripherals.button_d_pressed
    if cur_btn and not prev_btn:
        print("Show Result")
        time.sleep(0.1)
        break
    prev_btn = cur_btn

Before we actually start using the deck, we want to make sure it isn't in the same order every time. Circuitpython doesn't have access to the random.shuffle() function, but we can fake it by using the built in function sorted() and indexes from random.random() to achieve the same effect. 

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cards = sorted(cards, key=lambda _: random.random())

When we want to display text, we use the built in magtag set_text function. By using wrap_nicely, we can make sure that the card text won't ever go off the side of the magtag - note that characters from other languages (like Hiragana) can be larger than roman ones, so expect to change the length parameter based on the kind of text you want to display.

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# Example Hira wrapping (fewer characters)
text = '\n'.join(magtag.wrap_nicely(card[1], 11))
# Example Roman wrapping (more characters)
text += '\n'.join(magtag.wrap_nicely(card[2], 20))
# Set the contents of the text field
magtag.set_text(text)

We combine all these elements into the program's final main loop, which will run through the cards in a random order forever, waiting on user button presses to move forward.

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while True:
    # Shuffle the deck
    cards = sorted(cards, key=lambda _: random.random())
    for card in cards:

        # Show the first side and wait for the D button
        text = ''.join(magtag.wrap_nicely(card[0], 20))
        magtag.set_text(text)
        while True:
            cur_btn = magtag.peripherals.button_d_pressed
            if cur_btn and not prev_btn:
                print("Show Result")
                time.sleep(0.1)
                break
            prev_btn = cur_btn

        # Show the second side and wait for the D button
        text = '\n'.join(magtag.wrap_nicely(card[1], 11))
        text += '\n'
        text += '\n'.join(magtag.wrap_nicely(card[2], 20))
        print(text)
        magtag.set_text(text)
        while True:
            cur_btn = magtag.peripherals.button_d_pressed
            if cur_btn and not prev_btn:
                print("Next Card")
                time.sleep(0.1)
                break
            prev_btn = cur_btn

Complicated Flashcards

Our simple flashcard app already has some advantages over physical cards. But there are other features we could add. We might want to narrow down the cards we want to study, or sort them into topics, and it would be nice to revisit cards that we got wrong and want to study again. We're also missing a lot of basic UI features like labels and feedback.

In this expanded example, we'll add some new features to make this app a little more advanced, such as:

  • A new JSON format to support multiple "chapters" of a deck
  • A simple menu, allowing us to pick specific parts of our deck to study from
  • New text areas to label the buttons and give the user more directions
  • NeoPixel feedback after a user hits a button (a nice-to-have, since the e-paper screen is sloooow)
  • Automatically add cards the user marks as "forgotten" back into the deck to be studied again.

Installing Project Code

To use with CircuitPython, you need to first install a few libraries, into the lib folder on your CIRCUITPY drive. Then you need to update code.py with the example script.

Thankfully, we 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, open the directory MagTag_Flashcards/chapters/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your CIRCUITPY drive.

Your CIRCUITPY drive should now look similar to the following image:

CIRCUITPY
Download Project Bundle
Copy Code 
# SPDX-FileCopyrightText: 2021 Anne Barela for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import time
import json
import terminalio
import digitalio
import random
from adafruit_display_shapes.rect import Rect
from adafruit_magtag.magtag import MagTag
magtag = MagTag()

# ---------------------------------
# Prepare text regions
# ---------------------------------

# Fetch list of chapters
MAX_LLEN = 8
data = {}
with open("deck.json") as fp:
    data = json.load(fp)
chap_list = list(data.keys())
num_chap = len(chap_list)
list_len = min(num_chap,MAX_LLEN)

# Print list of chapters
for i in range(list_len):
    magtag.add_text(
        text_font=terminalio.FONT,
        text_position=(10, 3+(i*10)),
        line_spacing=1.0,
        text_anchor_point=(0, 0), # Top left
        is_data=False,            # Text will be set manually
    )
    if i == 0:
        magtag.set_text("> " + chap_list[i], i, auto_refresh=False)
    else:
        magtag.set_text("  " + chap_list[i], i, auto_refresh=False)

# Add button labels at the bottom of the screen
BUTTON_TEXT_IDX = list_len
magtag.graphics.splash.append(Rect(0, magtag.graphics.display.height - 14,
                                   magtag.graphics.display.width,
                                   magtag.graphics.display.height, fill=0x0))
magtag.add_text(
    text_font=terminalio.FONT,
    text_position=(3, magtag.graphics.display.height - 14),
    text_color=0xFFFFFF,
    line_spacing=1.0,
    text_anchor_point=(0, 0), # Top left
    is_data=False,            # Text will be set manually
)
magtag.set_text("Select        Up          Down        Begin",
                BUTTON_TEXT_IDX, auto_refresh=False)

# Add message label at the top of the screen
MSG_TEXT_IDX = list_len + 1
magtag.add_text(
    text_font=terminalio.FONT,
    text_position=(3, magtag.graphics.display.height - 30),
    line_spacing=1.0,
    text_anchor_point=(0, 0), # Top left
    is_data=False,            # Text will be set manually
)
magtag.set_text("Press Begin to default to all chapters", MSG_TEXT_IDX)

# Empty text region for card displays
CARD_TEXT_IDX = list_len + 2
magtag.add_text(
    text_font="yasashi20.pcf",
    text_position=(
        magtag.graphics.display.width // 2,
        magtag.graphics.display.height // 2,
    ),
    line_spacing=0.85,
    text_anchor_point=(0.5, 0.5),
)

# Button management
curr_btns = [False] * 4
prev_btns = [False] * 4
BTN_A = 0
BTN_B = 1
BTN_C = 2
BTN_D = 3
def update_button(idx, pressed):
    curr_btns[idx] = pressed
    if curr_btns[idx] and not prev_btns[idx]:
        print("Exit menu")
        return True
    prev_btns[idx] = curr_btns[idx]
    return False

# Cursor settings
cursor_pos = 0
list_offset = 0
selected = [False] * num_chap
btn_updated = False

# ---------------------------------
# Program Loop
# ---------------------------------

while True:

    # ---------------------------------
    # Chapter Select
    # ---------------------------------

    while True:
        if btn_updated:
            # Clear default message only when items are selected
            if any(selected):
                magtag.set_text("", MSG_TEXT_IDX, auto_refresh=False)
            else:
                magtag.set_text("Press Begin to default to all chapters",
                                MSG_TEXT_IDX, auto_refresh=False)

            magtag.peripherals.neopixels.fill((128, 0, 0))
            for i in range(list_len):
                prefix = ""
                if i == cursor_pos:
                    prefix += ">"
                else:
                    prefix += " "
                if selected[i + list_offset]:
                    prefix += "*"
                else:
                    prefix += " "
                magtag.set_text(prefix + chap_list[i+list_offset],
                                i, auto_refresh=False)
            magtag.refresh()
            magtag.peripherals.neopixels.fill((0, 0, 0))
            btn_updated = False
        # UP
        if update_button(BTN_B, magtag.peripherals.button_b_pressed):
            cursor_pos -= 1
            btn_updated = True
        # DOWN
        if update_button(BTN_C, magtag.peripherals.button_c_pressed):
            cursor_pos += 1
            btn_updated = True
        # SELECT
        if update_button(BTN_A, magtag.peripherals.button_a_pressed):
            selected[cursor_pos + list_offset] = not selected[cursor_pos + list_offset]
            btn_updated = True
        # BEGIN
        if update_button(BTN_D, magtag.peripherals.button_d_pressed):
            # if nothing was selected, default to all decks
            magtag.peripherals.neopixels.fill((128, 0, 0))
            if not any(selected):
                selected = [True] * list_len
            break
        # detect if you're past the list bounds
        if cursor_pos == MAX_LLEN:
            cursor_pos = MAX_LLEN - 1
            if (num_chap - list_offset - 1) > MAX_LLEN:
                list_offset += 1

        if cursor_pos == -1:
            cursor_pos = 0
            if list_offset > 0:
                list_offset -= 1

    # ---------------------------------
    # Deck Loop
    # ---------------------------------

    # Clear the menu and message box
    for i in range(list_len):
        magtag.set_text("", i, auto_refresh=False)
    magtag.set_text("", MSG_TEXT_IDX,auto_refresh=False)

    # Grab the cards from the chapters we want, and shuffle them
    cards = []
    for i in range(len(selected)):
        if selected[i]:
            cards.extend(data[chap_list[i]])
    cards = sorted(cards, key=lambda _: random.random())

    # make a separate holding deck for cards the user gets wrong
    forgotten_cards = []

    exit_called = False
    while True:
        for card in cards:
            magtag.set_text("Exit          --          --          Turn Over",
                            BUTTON_TEXT_IDX,auto_refresh=False)
            text = '\n'.join(magtag.wrap_nicely(card[0], 11))
            magtag.set_text(text, CARD_TEXT_IDX)
            magtag.peripherals.neopixels.fill((0, 0, 0))

            while True:
                # EXIT
                if update_button(BTN_A, magtag.peripherals.button_a_pressed):
                    exit_called = True
                    break
                # TURN
                if update_button(BTN_D, magtag.peripherals.button_d_pressed):
                    break
            magtag.peripherals.neopixels.fill((128, 0, 0))
            if exit_called:
                break

            magtag.set_text("Exit          --          Forgot      Good",
                            BUTTON_TEXT_IDX,auto_refresh=False)
            text = '\n'.join(magtag.wrap_nicely(card[1], 11))
            text += '\n'
            text += '\n'.join(magtag.wrap_nicely(card[2], 20))
            magtag.set_text(text, CARD_TEXT_IDX)
            magtag.peripherals.neopixels.fill((0, 0, 0))

            while True:
                # EXIT
                if update_button(BTN_A, magtag.peripherals.button_a_pressed):
                    exit_called = True
                    break
                # FORGOT
                if update_button(BTN_C, magtag.peripherals.button_c_pressed):
                    forgotten_cards.append(card)
                    break
                # GOOD
                if update_button(BTN_D, magtag.peripherals.button_d_pressed):
                    break
            magtag.peripherals.neopixels.fill((128, 0, 0))
            if exit_called:
                break
            # Next card
        # If there were forgotten cards, make them the new deck and restart
        if forgotten_cards:
            cards = forgotten_cards
            forgotten_cards = []
        else:
            break

    # ---------------------------------
    # Complete and Reset
    # ---------------------------------

    # Show completion text if deck was finished
    if not exit_called:
        magtag.set_text("--            --          --          --",
                        BUTTON_TEXT_IDX,auto_refresh=False)
        magtag.set_text("Complete!", CARD_TEXT_IDX)
    else:
        exit_called = False

    # Clear and reprint list of chapters
    magtag.set_text("", CARD_TEXT_IDX, auto_refresh=False)
    for i in range(list_len):
        if i == 0:
            magtag.set_text("> " + chap_list[i], i, auto_refresh=False)
        else:
            magtag.set_text("  " + chap_list[i], i, auto_refresh=False)
    magtag.set_text("Select        Up          Down        Begin",
                    BUTTON_TEXT_IDX, auto_refresh=False)
    magtag.set_text("Press Begin to default to all chapters", MSG_TEXT_IDX)

    # Reset cursor:
    cursor_pos = 0
    list_offset = 0
    selected = [False] * list_len
    btn_updated = False

    # Done resetting, return to chapter selection
    magtag.peripherals.neopixels.fill((0, 0, 0))
View on GitHub

New Deck Format

For our new deck, we want to start organizing cards by "chapter" - like different topics in a language, or different chapters in a textbook. To do this, we use the key-value syntax in JSON.

Instead of being a big list of smaller lists, the top level is now equivalent to a Python Dictionary, using curly brackets {}. Each chapter name has a list of cards associated with it. In our final program, we'll be able to study chapters by themselves or combine them together using the list of chapter names.

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Copy Code 
{
    "Everyday Phrases":[
        ["You're Welcome", "どういたしまして", "Dō Itashimashite"],
        ["Good Morning", "おはよう ございます", "Ohayō gozaimasu"],
        ["Yes", "はい", "Hai"],
        ["No", "いいえ", "Iie"],
        ["Hello", "こんにちは", "Konnichi wa"],
        ["Please", "おねがい します", "Onegai Shimasu"],
        ["Excuse Me", "すみません", "Sumimasen"],
        ["Thank You", "ありがとう", "Arigatō"],
    ],
    "Days of the Week":[
        ["Monday","げつ　ようび","Getsu yōbi"],
        ["Tuesday","か　ようび","Ka yōbi"],
        ["Wednesday","すい　ようび","Sui yōbi"],
        ["Thursday","もく　ようび","Moku yōbi"],
        ["Friday","きん　ようび","Kin yōbi"],
        ["Saturday","ど　ようび","Do yōbi"],
        ["Sunday","にち　ようび","Nichi yōbi"],
    ],
    "Animals":[
        ["Dog","いぬ","Inu"],
        ["Cat","ねこ","Neko"],
        ["Horse","うま","Uma"],
        ["Monkey","さる","Saru"],
        ["Elephant","ぞう","Zō"],
        ["Rabbit","うさぎ","Usagi"],
    ]
}

Program Flow

This program has a couple of different modes, so we'll go over how it works first.

The user starts by seeing a list of the chapters in their deck, along with a line of button labels. Hitting the Begin button right away will simply combine all the cards into one big study session and start up, but they can also pick specific chapters to focus on.

Users can move up and down the list with the arrow buttons, and select different chapters with the select button. Once they've picked the chapters you want to study, the Begin button will start a session for only cards from those chapters.

After a user turns a card over, they can press the "Forgot" button to mark it as incorrect. Forgotten cards automatically get added to the end of the deck, so once they've finished the original set, they'll need to study those cards again.

Once every card has been marked "good", the session is complete! A congratulatory message shows, and the user returns to the menu.

Code Walkthrough

Setup:

Just like the previous version, we start by importing the libraries we need, but note that we're using a new one, Adafruit Shapes, which will be a part of our background display.

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Copy Code 
import time
import json
import terminalio
import digitalio
import random
from adafruit_display_shapes.rect import Rect
from adafruit_magtag.magtag import MagTag
magtag = MagTag()

The file import section comes with some extra steps.

If the user has a LOT of chapters, we won't be able to fit them all on the screen at once, so we set a maximum number of lists to display at one time with MAX_LLEN. Lists over this number won't be shown unless the list is scrolled down.

We're going to start off by displaying all the chapters in a list, so we extract their names into a variable called chap_list. We also store the total number of chapters with num_chap.

Finally, if the list of chapters is shorter than MAX_LLEN, we won't need to scroll. So we find the actual length of the list we're displaying by comparing the two variables and picking the minimum.

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MAX_LLEN = 8
data = {}
with open("deck.json") as fp:
    data = json.load(fp)
chap_list = list(data.keys())
num_chap = len(chap_list)
list_len = min(num_chap,MAX_LLEN)

After importing the deck, we set up the various text regions. We create one for each item in the menu list, and then add on the button labels, background shape, and a special message region for telling the user about the "default" option if they don't actually pick any chapters.

We also create an empty text region that will eventually hold the flashcards themselves. Since the user moves back and forth between the menu selection and the cards, we won't actually delete any objects when we change modes - instead, we'll just fill the menu-specific text fields with empty strings when in flashcard mode, and vice versa for menu mode.

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# Print list of chapters
for i in range(list_len):
    magtag.add_text(
        text_font=terminalio.FONT,
        text_position=(10, 3+(i*10)),
        line_spacing=1.0,
        text_anchor_point=(0, 0), # Top left
        is_data=False,            # Text will be set manually
    )
    if i == 0:
        magtag.set_text("> " + chap_list[i], i, auto_refresh=False)
    else:
        magtag.set_text("  " + chap_list[i], i, auto_refresh=False)

# Add button labels at the bottom of the screen
BUTTON_TEXT_IDX = list_len
magtag.graphics.splash.append(Rect(0, magtag.graphics.display.height - 14,
                                   magtag.graphics.display.width,
                                   magtag.graphics.display.height, fill=0x0))
magtag.add_text(
    text_font=terminalio.FONT,
    text_position=(3, magtag.graphics.display.height - 14),
    text_color=0xFFFFFF,
    line_spacing=1.0,
    text_anchor_point=(0, 0), # Top left
    is_data=False,            # Text will be set manually
)
magtag.set_text("Select        Up          Down        Begin", BUTTON_TEXT_IDX, auto_refresh=False)

# Add message label at the top of the screen
MSG_TEXT_IDX = list_len + 1
magtag.add_text(
    text_font=terminalio.FONT,
    text_position=(3, magtag.graphics.display.height - 30),
    line_spacing=1.0,
    text_anchor_point=(0, 0), # Top left
    is_data=False,            # Text will be set manually
)
magtag.set_text("Press Begin to default to all chapters", MSG_TEXT_IDX)

# Empty text region for card displays
CARD_TEXT_IDX = list_len + 2
magtag.add_text(
    text_font="yasashi20.pcf",
    text_position=(
        magtag.graphics.display.width // 2,
        magtag.graphics.display.height // 2,
    ),
    line_spacing=0.85,
    text_anchor_point=(0.5, 0.5),
)

Remember the button code from the simple flashcards example? We don't need to change it much, but we do need to support all 4 buttons rather than just one. So we adapt the old code into a new function that can determine out the button status by index (unfortunately, the magtag library attributes aren't indexable, so you still need to pass those in too).

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# Button management
curr_btns = [False] * 4
prev_btns = [False] * 4
BTN_A = 0
BTN_B = 1
BTN_C = 2
BTN_D = 3
def update_button(idx, pressed):
    curr_btns[idx] = pressed
    if curr_btns[idx] and not prev_btns[idx]:
        print("Exit menu")
        return True
    prev_btns[idx] = curr_btns[idx]
    return False

As the final part of the setup process, we need some miscellaneous variables like the cursor location, the scrolling offset for long lists, what list items have been selected, and whether any buttons have been updated. 

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cursor_pos = 0
list_offset = 0
selected = [False] * num_chap
btn_updated = False

Chapter Selection:

Now we can get started with the main program loop. The first screen the user sees is the chapter selection, where they can move a cursor up and down to select chapters. We've already printed out all the text on this screen in the setup stage, so this is basically just a big loop to read buttons.

We have four different button detectors. The Up and Down buttons change the cursor position, Select changes the status of the chapter in the Selected array, and Begin signals to exit the loop and start studying flashcards (combining all of the chapters, if nothing was selected).

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# UP
if update_button(BTN_B, magtag.peripherals.button_b_pressed):
    cursor_pos -= 1
    btn_updated = True
# DOWN
if update_button(BTN_C, magtag.peripherals.button_c_pressed):
    cursor_pos += 1
    btn_updated = True
# SELECT
if update_button(BTN_A, magtag.peripherals.button_a_pressed):
    selected[cursor_pos + list_offset] = not selected[cursor_pos + list_offset]
    btn_updated = True
# BEGIN
if update_button(BTN_D, magtag.peripherals.button_d_pressed):
    # if nothing was selected, default to all decks
    magtag.peripherals.neopixels.fill((128, 0, 0))
    if not any(selected):
        selected = [True] * list_len
    break

If a button gets pressed, the program goes over the list of text areas and makes any required changes, like moving the cursor, adding * asterisks to selected chapters, and setting the current user message, all before refreshing the e-paper.

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if btn_updated:
    # Clear default message only when items are selected
    if any(selected):
        magtag.set_text("", MSG_TEXT_IDX, auto_refresh=False)
    else:
        magtag.set_text("Press Begin to default to all chapters",
                        MSG_TEXT_IDX, auto_refresh=False)

    magtag.peripherals.neopixels.fill((128, 0, 0))
    for i in range(list_len):
        prefix = ""
        if i == cursor_pos:
            prefix += ">"
        else:
            prefix += " "
        if selected[i + list_offset]:
            prefix += "*"
        else:
            prefix += " "
        magtag.set_text(prefix + chap_list[i+list_offset],
                        i, auto_refresh=False)
    magtag.refresh()
    magtag.peripherals.neopixels.fill((0, 0, 0))
    btn_updated = False

What's with the neopixel code? Since the e-paper updates slowly in comparison to how quickly we can push buttons, it's nice to give the user a little feedback that they've actually started an action.

So every time a button is pressed, we turn on the neopixels, and once the e-paper is finished updating and the buttons are ready to be pushed again, we turn it off. 

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magtag.peripherals.neopixels.fill((128, 0, 0))
magtag.peripherals.neopixels.fill((0, 0, 0))

Finally, if the chapter list is over the maximum list length, the user can scroll. This will only happen when the cursor is at the very end or very beginning of the list, and it doesn't affect things like chapter selection, which is the same no matter how the list is offset.

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if cursor_pos == MAX_LLEN:
    cursor_pos = MAX_LLEN - 1
    if (num_chap - list_offset - 1) > MAX_LLEN:
        list_offset += 1

if cursor_pos == -1:
    cursor_pos = 0
    if list_offset > 0:
        list_offset -= 1

Flashcard Session:

Once a user picks a chapter and hits begin, they move into the deck loop. This is where flashcards get displayed, and it's similar to the basic example earlier in this chapter, with a few additions. First, we clear all the text from the menu mode:

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# Clear the menu and message box
for i in range(list_len):
    magtag.set_text("", i, auto_refresh=False)
magtag.set_text("", MSG_TEXT_IDX,auto_refresh=False)

Then, we create a list of cards for this specific session, by combining all the cards from the chapters that were selected in the menu, and shuffling them.

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cards = []
for i in range(len(selected)):
    if selected[i]:
        cards.extend(data[chap_list[i]])
cards = sorted(cards, key=lambda _: random.random())

In python, you can't add to a list while you're iterating through it. Since we want to keep extending the deck with cards that the user forgot, we'll create a temporary holding list called "forgotten_cards", and add it on later. We'll also create a variable to detect whether the user wants to give up and go back to the menu.

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forgotten_cards = []
exit_called = False

Then, we enter the card loop. This is almost the same as the simple example. The only differences are that the user can exit the loop using the Exit button, or add cards to the forgotten_cards list with the Forget button. If there are any cards in forgotten_cards once the loop is finished, it'll restart the loop with those cards as the new deck, over and over until the user has gotten them all correct.

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while True:
    for card in cards:
        magtag.set_text("Exit          --          --          Turn Over",
                        BUTTON_TEXT_IDX,auto_refresh=False)
        text = '\n'.join(magtag.wrap_nicely(card[0], 11))
        magtag.set_text(text, CARD_TEXT_IDX)
        magtag.peripherals.neopixels.fill((0, 0, 0))

        while True:
            # EXIT
            if update_button(BTN_A, magtag.peripherals.button_a_pressed):
                exit_called = True
                break
            # TURN
            if update_button(BTN_D, magtag.peripherals.button_d_pressed):
                break
        magtag.peripherals.neopixels.fill((128, 0, 0))
        if exit_called:
            break

        magtag.set_text("Exit          --          Forgot      Good",
                        BUTTON_TEXT_IDX,auto_refresh=False)
        text = '\n'.join(magtag.wrap_nicely(card[1], 11))
        text += '\n'
        text += '\n'.join(magtag.wrap_nicely(card[2], 20))
        magtag.set_text(text, CARD_TEXT_IDX)
        magtag.peripherals.neopixels.fill((0, 0, 0))

        while True:
            # EXIT
            if update_button(BTN_A, magtag.peripherals.button_a_pressed):
                exit_called = True
                break
            # FORGOT
            if update_button(BTN_C, magtag.peripherals.button_c_pressed):
                forgotten_cards.append(card)
                break
            # GOOD
            if update_button(BTN_D, magtag.peripherals.button_d_pressed):
                break
        magtag.peripherals.neopixels.fill((128, 0, 0))
        if exit_called:
            break
        # Next card
    # If there were forgotten cards, make them the new deck and restart
    if forgotten_cards:
        cards = forgotten_cards
        forgotten_cards = []
    else:
        break

Wrapping up:

Once the user has finished a study session, all that's left is to clean up the screen and reset everything back to how it started. We'll send them a message if they completed the deck (rather than exiting), and turn off any LEDs or variables that might have been set.

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# Show completion text if deck was finished
if not exit_called:
    magtag.set_text("--            --          --          --",
                    BUTTON_TEXT_IDX,auto_refresh=False)
    magtag.set_text("Complete!", CARD_TEXT_IDX)
else:
    exit_called = False

# Clear and reprint list of chapters
magtag.set_text("", CARD_TEXT_IDX, auto_refresh=False)
for i in range(list_len):
    if i == 0:
        magtag.set_text("> " + chap_list[i], i, auto_refresh=False)
    else:
        magtag.set_text("  " + chap_list[i], i, auto_refresh=False)
magtag.set_text("Select        Up          Down        Begin",
                BUTTON_TEXT_IDX, auto_refresh=False)
magtag.set_text("Press Begin to default to all chapters", MSG_TEXT_IDX)

# Reset cursor:
cursor_pos = 0
list_offset = 0
selected = [False] * list_len
btn_updated = False

# Done resetting, return to chapter selection
magtag.peripherals.neopixels.fill((0, 0, 0))

Other Resources

Flashcard science is actually a surprisingly broad and well-researched topic! There are lots of modifications that could be added to a program like this to help you learn faster, but weren't a good fit for this tutorial.

The example programs given here should be a good start, but if you'd looking for inspiration on creating your own flashcards, or making modifications to this example program, you can check out the following links.

Font License:

This guide uses the Yasashisa Gothic (やさしさゴシック) font. It's free for both personal and commercial projects, and uses the IPA license.

IPA summary from TLDRLegal:

The IPA license applies only to font programs and allows for a great deal of freedom in distributing them, both commercially and non-commercially. You cannot change the name of redistributed versions of the original software and must include a copy of the license, however.

 

This guide was first published on Jan 06, 2021. It was last updated on Jan 06, 2021.