Your project will use a specific set of CircuitPython libraries and the code.py file, along with a folder full of key configuration files. To get everything you need, click on the Download Project Bundle link below, and uncompress the .zip file.

Drag the contents of the uncompressed bundle directory onto your MACROPAD board's CIRCUITPY drive, replacing any existing files or directories with the same names, and adding any new ones that are necessary.

# SPDX-FileCopyrightText: 2021 Carter Nelson for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import time
# base hardware stuff
import board
import rtc
import keypad
import rotaryio
import neopixel
# crypto stuff
import adafruit_pcf8523
import adafruit_hashlib as hashlib
# UI stuff
import displayio
import terminalio
from adafruit_bitmap_font import bitmap_font
from adafruit_display_text import label
from adafruit_progressbar.horizontalprogressbar import HorizontalProgressBar
# HID keyboard stuff
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keyboard_layout_us import KeyboardLayoutUS
from adafruit_hid.keycode import Keycode

#--| User Config |--------------------------------------------------------
UTC_OFFSET = -4        # time zone offset
USE_12HR = True        # set 12/24 hour format
DISPLAY_TIMEOUT = 60   # screen saver timeout in seconds
DISPLAY_RATE = 1       # screen refresh rate
#-------------------------------------------------------------------------

# Get secrets from a secrets.py file
try:
    from secrets import secrets
    totp_keys = secrets["totp_keys"]
except ImportError:
    print("Secrets are kept in secrets.py, please add them there!")
    raise
except KeyError:
    print("TOTP info not found in secrets.py.")
    raise

# set board to use PCF8523 as its RTC
pcf = adafruit_pcf8523.PCF8523(board.I2C())
rtc.set_time_source(pcf)

#-------------------------------------------------------------------------
#                       H I D    S E T U P
#-------------------------------------------------------------------------
time.sleep(1)  # Sleep for a bit to avoid a race condition on some systems
keyboard = Keyboard(usb_hid.devices)
keyboard_layout = KeyboardLayoutUS(keyboard)  # We're in the US :)

#-------------------------------------------------------------------------
#                    D I S P L A Y    S E T U P
#-------------------------------------------------------------------------
display = board.DISPLAY

# Secret Code font by Matthew Welch
# http://www.squaregear.net/fonts/
font = bitmap_font.load_font("/secrcode_28.bdf")

name = label.Label(terminalio.FONT, text="?"*18, color=0xFFFFFF)
name.anchor_point = (0.0, 0.0)
name.anchored_position = (0, 0)

code = label.Label(font, text="123456", color=0xFFFFFF)
code.anchor_point = (0.5, 0.0)
code.anchored_position = (display.width // 2, 15)

rtc_date = label.Label(terminalio.FONT, text="2021/01/01")
rtc_date.anchor_point = (0.0, 0.5)
rtc_date.anchored_position = (0, 49)

rtc_time = label.Label(terminalio.FONT, text="12:34:56 AM")
rtc_time.anchor_point = (0.0, 0.5)
rtc_time.anchored_position = (0, 59)

progress_bar = HorizontalProgressBar((68, 46), (55, 17), bar_color=0xFFFFFF, min_value=0, max_value=30)

splash = displayio.Group()
splash.append(name)
splash.append(code)
splash.append(rtc_date)
splash.append(rtc_time)
splash.append(progress_bar)

display.show(splash)

#-------------------------------------------------------------------------
#                    H E L P E R    F U N C S
#-------------------------------------------------------------------------
def timebase(timetime):
    return (timetime - (UTC_OFFSET*3600)) // 30

def compute_codes(timestamp):
    codes = []
    for key in totp_keys:
        if key:
            codes.append(generate_otp(timestamp, key[1]))
        else:
            codes.append(None)
    return codes

def HMAC(k, m):
    """# HMAC implementation, as hashlib/hmac wouldn't fit
    From https://en.wikipedia.org/wiki/Hash-based_message_authentication_code

    """
    SHA1_BLOCK_SIZE = 64
    KEY_BLOCK = k + (b'\0' * (SHA1_BLOCK_SIZE - len(k)))
    KEY_INNER = bytes((x ^ 0x36) for x in KEY_BLOCK)
    KEY_OUTER = bytes((x ^ 0x5C) for x in KEY_BLOCK)
    inner_message = KEY_INNER + m
    outer_message = KEY_OUTER + hashlib.sha1(inner_message).digest()
    return hashlib.sha1(outer_message)

def base32_decode(encoded):
    missing_padding = len(encoded) % 8
    if missing_padding != 0:
        encoded += '=' * (8 - missing_padding)
    encoded = encoded.upper()
    chunks = [encoded[i:i + 8] for i in range(0, len(encoded), 8)]

    out = []
    for chunk in chunks:
        bits = 0
        bitbuff = 0
        for c in chunk:
            if 'A' <= c <= 'Z':
                n = ord(c) - ord('A')
            elif '2' <= c <= '7':
                n = ord(c) - ord('2') + 26
            elif c == '=':
                continue
            else:
                raise ValueError("Not base32")
            # 5 bits per 8 chars of base32
            bits += 5
            # shift down and add the current value
            bitbuff <<= 5
            bitbuff |= n
            # great! we have enough to extract a byte
            if bits >= 8:
                bits -= 8
                byte = bitbuff >> bits  # grab top 8 bits
                bitbuff &= ~(0xFF << bits)  # and clear them
                out.append(byte)  # store what we got
    return out

def int_to_bytestring(int_val, padding=8):
    result = []
    while int_val != 0:
        result.insert(0, int_val & 0xFF)
        int_val >>= 8
    result = [0] * (padding - len(result)) + result
    return bytes(result)

def generate_otp(int_input, secret_key, digits=6):
    """ HMAC -> OTP generator, pretty much same as
    https://github.com/pyotp/pyotp/blob/master/src/pyotp/otp.py

    """
    if int_input < 0:
        raise ValueError('input must be positive integer')
    hmac_hash = bytearray(
        HMAC(bytes(base32_decode(secret_key)),
             int_to_bytestring(int_input)).digest()
    )
    offset = hmac_hash[-1] & 0xf
    code = ((hmac_hash[offset] & 0x7f) << 24 |
            (hmac_hash[offset + 1] & 0xff) << 16 |
            (hmac_hash[offset + 2] & 0xff) << 8 |
            (hmac_hash[offset + 3] & 0xff))
    str_code = str(code % 10 ** digits)
    while len(str_code) < digits:
        str_code = '0' + str_code

    return str_code

#-------------------------------------------------------------------------
#                    M A C R O P A D    S E T U P
#-------------------------------------------------------------------------
key_pins = (
    board.KEY1,
    board.KEY2,
    board.KEY3,
    board.KEY4,
    board.KEY5,
    board.KEY6,
    board.KEY7,
    board.KEY8,
    board.KEY9,
    board.KEY10,
    board.KEY11,
    board.KEY12,
    board.BUTTON,
)

keys = keypad.Keys(key_pins, value_when_pressed=False, pull=True)

knob = rotaryio.IncrementalEncoder(board.ROTA, board.ROTB)

pixels = neopixel.NeoPixel(board.NEOPIXEL, 12)
pixels.fill(0)

######################################
# MAIN
######################################
awake = True
knob_pos = knob.position
current_key = key_pressed = 0
last_compute = last_update = wake_up_time = time.time()
totp_codes = compute_codes(timebase(last_compute))
while True:
    now = time.time()
    progress_bar.value = now % 30
    event = keys.events.get()
    # wakeup if knob turned or button pressed
    if knob.position != knob_pos or event:
        if not awake:
            last_update = 0 # force an update
        awake = True
        knob_pos = knob.position
        wake_up_time = now
    # handle key presses
    if event:
        if event.pressed:
            key_pressed = event.key_number
            # knob
            if key_pressed == 12:
                keyboard_layout.write(totp_codes[current_key])
                keyboard.send(Keycode.ENTER)
            # keeb
            elif key_pressed != current_key:
                # is it a configured key?
                if totp_keys[key_pressed]:
                    current_key = key_pressed
                    pixels.fill(0)
                    last_update = 0 # force an update
    # update codes
    if progress_bar.value < 0.5 and now - last_compute > 2:
        totp_codes = compute_codes(timebase(now))
        last_compute = now
    # update display
    if now - last_update > DISPLAY_RATE and awake:
        pixels[current_key] = totp_keys[current_key][2]
        name.text = totp_keys[current_key][0][:18]
        code.text = totp_codes[current_key]
        tt = time.localtime()
        if USE_12HR:
            hour = tt.tm_hour % 12
            ampm = "AM" if tt.tm_hour < 12 else "PM"
        else:
            hour = tt.tm_hour
            ampm = ""
        rtc_date.text = "{:4}/{:2}/{:2}".format(tt.tm_year, tt.tm_mon, tt.tm_mday)
        rtc_time.text = "{}:{:02}:{:02} {}".format(hour, tt.tm_min, tt.tm_sec, ampm)
        last_update = now
        splash.hidden = False
    # go to sleep after inactivity
    if awake and now - wake_up_time > DISPLAY_TIMEOUT:
        awake = False
        knob_pos = knob.position
        pixels.fill(0)
        splash.hidden = True

This guide was first published on Jul 19, 2021. It was last updated on Jul 19, 2021.

This page (Project Code) was last updated on May 24, 2022.

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