Introduction¶

CircuitPython driver for 74HC595 shift register.

Dependencies¶

This driver depends on:

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle.

Installing from PyPI¶

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:

pip3 install adafruit-circuitpython-74hc595

To install system-wide (this may be required in some cases):

sudo pip3 install adafruit-circuitpython-74hc595

To install in a virtual environment in your current project:

mkdir project-name && cd project-name
python3 -m venv .env
source .env/bin/activate
pip3 install adafruit-circuitpython-74hc595

Usage Example¶

import board
import adafruit_74hc595
import busio
import digitalio
import time

spi = busio.SPI(board.SCK, MOSI=board.MOSI)

latch_pin = digitalio.DigitalInOut(board.D5)
sr = adafruit_74hc595.ShiftRegister74HC595(spi, latch_pin)

pin1 = sr.get_pin(1)

while True:
    pin1.value = True
    time.sleep(1)
    pin1.value = False
    time.sleep(1)

Contributing¶

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.

Documentation¶

For information on building library documentation, please check out this guide.

Table of Contents¶

Simple test¶

Ensure your device works with this simple test.

examples/74hc595_simpletest.py¶

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

import time
import board
import busio
import digitalio
import adafruit_74hc595

spi = busio.SPI(board.SCK, MOSI=board.MOSI)

latch_pin = digitalio.DigitalInOut(board.D5)
sr = adafruit_74hc595.ShiftRegister74HC595(spi, latch_pin)

pin1 = sr.get_pin(1)

while True:
    pin1.value = True
    time.sleep(1)
    pin1.value = False
    time.sleep(1)

`adafruit_74hc595`¶

CircuitPython driver for 74HC595 shift register.

Author(s): Kattni Rembor, Tony DiCola

Implementation Notes¶

Hardware:

“* 74HC595 Shift Register - 3 pack”

Software and Dependencies:

Adafruit CircuitPython firmware for the supported boards: https://github.com/adafruit/circuitpython/releases
Adafruit’s Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice

class adafruit_74hc595.DigitalInOut(pin_number, shift_register_74hc595)¶

Digital input/output of the 74HC595. The interface is exactly the same as the digitalio.DigitalInOut class, however note that by design this device is OUTPUT ONLY! Attempting to read inputs or set direction as input will raise an exception.

direction¶: Direction can only be set to OUTPUT.

pull¶: Pull-up/down not supported, return None for no pull-up/down.

switch_to_input(**kwargs)¶: switch_to_input is not supported.

switch_to_output(value=False, **kwargs)¶: DigitalInOut switch_to_output

value¶: The value of the pin, either True for high or False for low.

class adafruit_74hc595.ShiftRegister74HC595(spi, latch)¶

Initialise the 74HC595 on specified SPI bus.

get_pin(pin)¶: Convenience function to create an instance of the DigitalInOut class pointing at the specified pin of this 74HC595 device .

gpio¶: The raw GPIO output register. Each bit represents the output value of the associated pin (0 = low, 1 = high).