Now let's get the Feather setup with CircuitPython, the necessary libraries, and the hourglass code.

Prepare the Feather Sense

Follow this guide for setting up CircuitPython on the Feather nRF52840 Sense:

Hourglass Code

Click the Download Project Bundle button in the code listing below to get a zip file with the project code and necessary libraries. Copy and to the CIRCUITPY folder.

Also copy the libraries to CIRCUITPY/lib. For quick reference, the CIRCUITPY/lib folder should have these contents (having more is OK):

Here is the main code listing for The file will be found in the zip, along with everything else. Click the Download Project Bundle to get the zip.

# SPDX-FileCopyrightText: 2020 Carter Nelson for Adafruit Industries
# SPDX-License-Identifier: MIT

import time
import board
import adafruit_lsm6ds.lsm6ds33
from adafruit_ht16k33 import matrix
import matrixsand

DELAY = 0.05 # overall update rate

# setup i2c
i2c = board.I2C()  # uses board.SCL and board.SDA
# i2c = board.STEMMA_I2C()  # For using the built-in STEMMA QT connector on a microcontroller

# the accelo
accelo = adafruit_lsm6ds.lsm6ds33.LSM6DS33(i2c)

# the matrices
m1 = matrix.Matrix8x8(i2c, 0x70)
m2 = matrix.Matrix8x8(i2c, 0x71)

# the sand
sand1 = matrixsand.MatrixSand(8, 8)
sand2 = matrixsand.MatrixSand(8, 8)

# simple helper
def update_matrix(m, s):
    for x in range(8):
        for y in range(8):
            m[x,y] = s[x,y]

# fill up some sand
for sx in range(8):
    for sy in range(8):
        sand1[sx, sy] = True
sand1[0,0] = sand1[0,1] = sand1[1,0] = False
sand1[0,2] = sand1[1,1] = sand1[2,0] = False

update_matrix(m1, sand1)
update_matrix(m2, sand2)

updated1 = updated2 = False

while True:
    # read accelo
    ax, ay, az = accelo.acceleration
    # rotate coords
    xx = -ax - ay
    yy = -ax + ay
    zz = az

    # move grain of sand from upper to lower?
    if yy > 0 and sand1[7,7] and not sand2[0,0] and not updated2:
        sand1[7,7] = False
        sand2[0,0] = True
        updated1 = updated2 = True
    # move grain of sand from lower to upper?
    elif yy <= 0 and sand2[0,0] and not sand1[7,7] and not updated1:
        sand2[0,0] = False
        sand1[7,7] = True
        updated1 = updated2 = True
    # nope, just a regular update
        updated1 = sand1.iterate((xx, yy, zz))
        updated2 = sand2.iterate((xx, yy, zz))

    # update matrices if needed
    if updated1:
        update_matrix(m1, sand1)
    if updated2:
        update_matrix(m2, sand2)


This guide was first published on Jul 07, 2020. It was last updated on Jun 17, 2024.

This page (Hourglass Code) was last updated on Jun 16, 2024.

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