A Fun Circuit Python Project

I’m starting to fall back in love with micro-controllers. I haven’t touched anything like an Arduino since my college days, and there is something to be said about the simplicity of the environment. I have a hard time with what to do on them, which is probably why I’ve owned an Adafruit MagTag for nearly 3 years and haven’t used it in any projects.

One day, I saw it on my shelf and decided to get back into it. I was going to make something that is actually useful, and then maybe learn something along the way! The Adafruit library has an interesting function that generates a QR code, and QR codes and E-ink was an interesting combo in my head, so I wanted to find a way to use it.

I finally settled on a random password generator. Simply click a button and the device would create a random and secure password for you to scan, then use.

The Code

The Circuit Python code below is used to generate a random value and display it as a QR code on an e-ink display using an ESP32 board for use as a password.

# import wifi # type: ignore
import time
import os
from adafruit_magtag.magtag import MagTag
import binascii

magtag = MagTag()
magtag.add_text(
text_position=(
50,
(magtag.graphics.display.height // 2) - 1,
),
text_scale=1,
)
password = binascii.b2a_base64(binascii.hexlify(os.urandom(16)))

def update_qr(code):

magtag.graphics.qrcode(password, qr_size=4, x=13, y=3,qr_color=1)
magtag.graphics.set_background("/img/background.bmp")
time.sleep(0.01)
magtag.refresh()

while True:
    for i, b in enumerate(magtag.peripherals.buttons):
        if not b.value:
            print("Button %c pressed" % chr((ord("A") + i)))

            if(i==0):
            password = binascii.b2a_base64(binascii.hexlify(os.urandom(8)))
            magtag.peripherals.neopixel_disable = False

            if(i==1):
                password = binascii.b2a_base64(binascii.hexlify(os.urandom(16)))
                magtag.peripherals.neopixel_disable = False
                time.sleep(0.1)
            break
        else:
            magtag.peripherals.neopixel_disable = True
                
        update_qr(password)

time.sleep(0.01)

• Import necessary libraries (e.g. adafruit_magtag for MagTag class) and initialize an instance of the MagTag class to access the e-ink display
• Define a function update_qr() that generates a random value using os.urandom() and converts it to a base64 string for encoding as a QR code
• Inside a while True loop, check if any buttons on the display are pressed, generate new random values accordingly, and update the QR code using the update_qr() function
• Use button press events to change random value generation length and enable/disable neopixel LEDs.

Finally

And there it is. A completely offline way to generate passwords for use by devices that can scan a QR code. There are several ways I think this should be improved, like adding symbols to the strings, randomizing the ratio of letters to numbers, and making use of the other 2 buttons. I can’t get over how much I enjoy the bitmap image in the background with the QR code. It’s such an interesting aesthetic and I absolutely love it.

What’s next?

I would like to make more projects with this hardware. I feel like there are some other boards I’d like to play with, but this projects gives me the confidence I felt I was missing to get back into microcontroller projects.