Getting familiar with CircuitPython

CircuitPython is a programming language based on Python, one of the fastest growing programming languages in the world. It is specifically designed to simplify experimenting and learning to code on low-cost microcontroller boards.

CircuitPython is easiest to use within the Mu Editor. If you haven't previously used Mu, this guide will get you started.

Preparing your Board

1) Download the latest 4.0 library pack,

2) Unzip it the library pack and drag the adafruit_bus_device, adafruit_ds3231, adafruit_register, and neopixel libraries over into the /lib folder on CIRCUITPY.

If there is no lib directory on your CIRCUITPY drive, create one to put the file into.

More info on installing libraries can be found here.

Make sure you have the following libraries installed: 

  • adafruit_bus_device
  • adafruit_ds3231
  • adafruit_register
  • neopixel

Setting the Time

First things first, let's tell the RTC FeatherWing what time it is! 

Copy and paste the code below into Mu. In line 22, fill in the correct year, month, day, hour, and minute. Save this as code.py to your CIRCUITPY device.

(More details on using the DS3231 Precision RTC can be found in this guide)

# Write the time for the Adafruit DS3231 real-time clock.
# Limor Fried/Mike Barela for Adafruit Industries

import time
import board
import busio as io
import digitalio
import adafruit_ds3231

i2c = io.I2C(board.SCL, board.SDA)

# Create the RTC instance:
rtc = adafruit_ds3231.DS3231(i2c)

LED13 = digitalio.DigitalInOut(board.D13)
LED13.direction = digitalio.Direction.OUTPUT

# pylint: disable-msg=bad-whitespace
# pylint: disable-msg=using-constant-test
if True:
    #                     year, mon, date, hour, min, sec, wday, yday, isdst
    t = time.struct_time((2019,   7,    10,   17,  00,   0,    0,   -1,    -1))
    # you must set year, mon, date, hour, min, sec and weekday
    # yearday is not supported
    # isdst can be set but we don't do anything with it at this time
    print("Setting time to:", t)     # uncomment for debugging
    rtc.datetime = t
    print("Done!")
    LED13.value = True
# pylint: enable-msg=using-constant-test
# pylint: enable-msg=bad-whitespace

Once the time has been set we're ready to move on to uploading the Wordclock code.

Vertical Wordclock Code

Make sure you've connected the Feather M4 Express to your computer (mac/PC/Linux) via a known good USB A to micro-B cable. Your board should show up as a flash disk drive named CIRCUITPY (If you see a disk name FEATHERBOOT, try pressing the reset button again. If the only drive name you get is named FEATHERBOOT, CircuitPython may not be loaded on the board. You can load CircuitPython as per this guide).

Once your board is connected, copy the code below from the window below to a file on the Feather CIRCUITPY drive as code.py. You can select Download in the upper left to save the code onto your computer.

# Vertical Word Clock using the Adafruit Feather M4 and
#   the Adafruit DS3231 real-time clock FeatherWing

import time
import board
import busio as io
import digitalio
import adafruit_ds3231
import neopixel

i2c = io.I2C(board.SCL, board.SDA)

# Create the RTC instance:
rtc = adafruit_ds3231.DS3231(i2c)

# Set up Feather M4 onboard LED for output
LED13 = digitalio.DigitalInOut(board.D13)
LED13.direction = digitalio.Direction.OUTPUT

# Set digital 6 as an input for slide switch
Slide_Switch = digitalio.DigitalInOut(board.D6)
Slide_Switch.switch_to_input(pull=digitalio.Pull.UP)

pixel_pin = board.D5
num_pixels = 21
pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=1.0,
                           auto_write=False)
pixels.fill((0, 0, 0))  # Blanking Display
COLOR = (0, 200, 0)     # Green for time later in code

# Bitmap values for each value. These can be OR'ed together
THREE = 1
EIGHT = 1 << 1
ELEVEN = 1 << 2
TWO = 1 << 3
SIX = 1 << 4
FOUR = 1 << 5
SEVEN = 1 << 6
NOON = 1 << 7
TEN = 1 << 8
ONE = 1 << 9
FIVE = 1 << 10
MIDNIGHT = 1 << 11
NINE = 1 << 12
PAST = 1 << 13
TO = 1 << 14
FIVEMIN = 1 << 15
QUARTER = 1 << 16
TENMIN = 1 << 17
HALF = 1 << 18
TWENTY = 1 << 19

# Pass in hour and minute, return LED bitmask
# pylint: disable=too-many-branches
# pylint: disable=too-many-statements
def writetime(the_hr, the_min):
    value = 0  # Start with zero, which is no words
    if (the_hr == 24) and (the_min == 0):  # Special cases: Midnight and Noon
        return MIDNIGHT
    if (the_hr == 12) and (the_min == 0):
        return NOON
    # set minute
    if (the_min > 3) and (the_min < 8):
        value = value | FIVEMIN
    if (the_min > 7) and (the_min < 13):
        value = value | TENMIN
    if (the_min > 12) and (the_min < 18):
        value = value | QUARTER
    if (the_min > 17) and (the_min < 23):
        value = value | TWENTY
    if (the_min > 22) and (the_min < 28):
        value = value | TWENTY | FIVEMIN
    if (the_min > 27) and (the_min < 33):
        value = value | HALF
    if (the_min > 32) and (the_min < 38):
        value = value | TWENTY | FIVEMIN
    if (the_min > 37) and (the_min < 43):
        value = value | TWENTY
    if (the_min > 42) and (the_min < 48):
        value = value | QUARTER
    if (the_min > 47) and (the_min <= 53):
        value = value | TENMIN
    if the_min >= 54:
        value = value | FIVEMIN
    # before or after
    if (the_min > 3) and (the_min <= 32):
        value = value | PAST
    if the_min >= 33:
        the_hr = the_hr + 1  # for the TO case
        value = value | TO
    # set hour
    if the_hr > 12:
        the_hr = the_hr - 12  # Convert 24 hour format to 12 hour
    if the_hr == 1:
        value = value | ONE
    if the_hr == 2:
        value = value | TWO
    if the_hr == 3:
        value = value | THREE
    if the_hr == 4:
        value = value | FOUR
    if the_hr == 5:
        value = value | FIVE
    if the_hr == 6:
        value = value | SIX
    if the_hr == 7:
        value = value | SEVEN
    if the_hr == 8:
        value = value | EIGHT
    if the_hr == 9:
        value = value | NINE
    if the_hr == 10:
        value = value | TEN
    if the_hr == 11:
        value = value | ELEVEN
    if the_hr == 0:
        value = value | MIDNIGHT
    if the_hr == 12:
        value = value | NOON
    return value
# end def
# pylint: enable=too-many-branches
# pylint: enable=too-many-statements

# Main loop
LEDstate = 0
Write_Now = True

while True:
    t = rtc.datetime
    # print("The date is {} {}/{}/{}".format(days[int(t.tm_wday)],
    #        t.tm_mday, t.tm_mon, t.tm_year))
    # print("The time is {}:{:02}:{:02}".format(t.tm_hour, t.tm_min, t.tm_sec))
    hour = t.tm_hour
    if not Slide_Switch.value:  # Slide switch activate = Daylight savings
        # print("Switch detected for daylight savings")
        if hour == 24:
            hour = 1
        else:
            hour += 1
        Write_Now = True  # Trigger a write
    minute = t.tm_min
    second = t.tm_sec
    if second == 59 or Write_Now:
        # print("The time is {}:{:02}".format(t.tm_hour, t.tm_min))
        pixels.fill((0, 0, 0))       # blank all pixels for change
        the_time = writetime(hour, minute)
        for i in range(0, 21):       # Check all bits
            if the_time & 1 << i:    # If the bit is true
                pixels[i+1] = COLOR  # set pixel on (shift up 2 for buried one)
        pixels.show()
    if LEDstate == 0:       # Flash the D13 LED every other second for activity
        LED13.value = True
        LEDstate = 1
    else:
        LED13.value = False
        LEDstate = 0
    Write_Now = False
    time.sleep(1)  # wait a second

Open the code up in the Mu editor. Press the Save button and your code should automatically be saved to the CIRCUITPY disk drive (which appears when the Feather M4 Express is plugged into your computer) as code.py

Make sure the file saved to CIRCUITPY is named "code.py", this will allow it to run automatically when your Feather is powered on.

Making Changes

If you'd like to adjust the color of your clock, this can be changed in line 29 of the code. Simply change the numbers in COLOR = (0, 200, 0) (green) - make the clock glow blue (0, 0, 200) or red (200, 0, 0), or any color in between! A great color picker is at https://www.w3schools.com/colors/colors_picker.asp.

This guide was first published on Jul 12, 2019. It was last updated on Jul 12, 2019.

This page (CircuitPython) was last updated on Jun 16, 2021.

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