Trinket M0 and Gemma M0 boards can run CircuitPython — a different approach to programming compared to Arduino sketches. In fact, CircuitPython comes factory pre-loaded on Trinket M0. If you’ve overwritten it with an Arduino sketch, or just want to learn the basics of setting up and using CircuitPython, this is explained in the Adafruit Trinket M0 guide or Adafruit Gemma M0 guide.
Below is CircuitPython code that works similarly (though not exactly the same) as the Arduino sketch shown on a prior page. To use this, plug the Trinket M0 into USB…it should show up on your computer as a small flash drive…then edit the file “main.py” with your text editor of choice. Select and copy the code below and paste it into that file, entirely replacing its contents (don’t mix it in with lingering bits of old code). When you save the file, the code should start running almost immediately (if not, see notes at the bottom of this page).
If Trinket M0 doesn’t show up as a drive, follow the Trinket M0 guide link above to prepare the board for CircuitPython.
# SPDX-FileCopyrightText: 2018 Mikey Sklar for Adafruit Industries
#
# SPDX-License-Identifier: GPL-3.0-or-later
"""
Blinking Eyes - based on code by Brad Blumenthal, MAKE Magazine
License: GPLv3
"""
import time
import analogio
import board
import pwmio
try:
import urandom as random # for v1.0 API support
except ImportError:
import random
# Initialize photocell
photocell_pin = board.A1 # cds photocell connected to this ANALOG pin
darkness_max = (2 ** 16 / 2) # more dark than light > 32k out of 64k
photocell = analogio.AnalogIn(photocell_pin)
# Initialize PWM
# PWM (fading) - Both LEDs are connected on D0
# (PWM not avail on D1)
pwm_leds = board.D0
pwm = pwmio.PWMOut(pwm_leds, frequency=1000, duty_cycle=0)
brightness = 0 # how bright the LED is
fade_amount = 1285 # 2% steping of 2^16
counter = 0 # counter to keep track of cycles
# blink delay
blink_delay = True
blink_freq_min = 3
blink_freq_max = 6
# Loop forever...
while True:
# turn on LEDs if it is dark out
if photocell.value < darkness_max:
# blink frequency and timer
if blink_delay:
blink_delay = False
blink_timer_start = time.monotonic()
blink_freq = random.randint(blink_freq_min, blink_freq_max)
# time to blink? Blink once every 3 - 6 seconds (random assingment)
if (time.monotonic() - blink_timer_start) >= blink_freq:
blink_delay = True
pwm.duty_cycle = 0
time.sleep(.1)
# send to LED as PWM level
pwm.duty_cycle = brightness
# change the brightness for next time through the loop:
brightness = brightness + fade_amount
# reverse the direction of the fading at the ends of the fade:
if brightness <= 0:
fade_amount = -fade_amount
counter += 1
elif brightness >= 65535:
fade_amount = -fade_amount
counter += 1
# wait for 15 ms to see the dimming effect
time.sleep(.015)
else:
# shutoff LEDs, it is too bright
pwm.duty_cycle = 0
Page last edited December 01, 2025
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