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https://github.com/mcauser/micropython-pcf8574

MicroPython driver for PCF8574 8-Bit I2C I/O Expander with Interrupt
https://github.com/mcauser/micropython-pcf8574

io-expander micropython pcf8574

Last synced: 21 days ago
JSON representation

MicroPython driver for PCF8574 8-Bit I2C I/O Expander with Interrupt

Host: GitHub
URL: https://github.com/mcauser/micropython-pcf8574
Owner: mcauser
License: mit
Created: 2019-11-28T04:53:50.000Z (almost 5 years ago)
Default Branch: master
Last Pushed: 2024-02-11T04:11:05.000Z (9 months ago)
Last Synced: 2024-04-22T12:34:43.790Z (7 months ago)
Topics: io-expander, micropython, pcf8574
Language: Python
Size: 2.64 MB
Stars: 32
Watchers: 5
Forks: 4
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE.txt

Awesome Lists containing this project

awesome-micropython - micropython-pcf8574 - MicroPython driver for PCF8574 8-Bit I2C I/O Expander with Interrupt. (Libraries / IO)

README

        # MicroPython PCF8574

A MicroPython library for PCF8574 8-Bit I2C I/O Expander with Interrupt.

![demo](docs/demo.jpg)

The PCF8574 consists of a 8-bit quasi-bidirectional port and an I2C-bus interface.

The device includes latched outputs with high current drive capability for directly driving LEDs.

The interrupt has an open-drain output, which means you need a pull-up on your microcontroller

to detect when the PCF8574 drives it LOW.

When setting a pin HIGH, it acts as both output AND input. The pin internally uses a weak

current-source pull-up to latch output HIGH.

When driven LOW, for example, with a push button, the pin will read as LOW.

An interrupt fires on any rising or falling edge of the pins in input mode (HIGH).

Interrupt is cleared when the pins are changed or the port is read.

At power on, all pins are driven HIGH and can be immediately used as inputs.

Operating voltage: 2.5V - 5.5V

## Installation

Using mip via mpremote:

```bash

$ mpremote mip install github:mcauser/micropython-pcf8574

$ mpremote mip install github:mcauser/micropython-pcf8574/examples

```

Using mip directly on a WiFi capable board:

```python

>>> import mip

>>> mip.install("github:mcauser/micropython-pcf8574")

>>> mip.install("github:mcauser/micropython-pcf8574/examples")

```

Manual installation:

Copy `src/pcf8574.py` to the root directory of your device.

## Examples

**Basic Usage**

```python

import pcf8574

from machine import I2C, Pin

# TinyPICO (ESP32)

i2c = I2C(0)

pcf = pcf8574.PCF8574(i2c, 0x20)

# read pin 2

pcf.pin(2)

# set pin 3 HIGH

pcf.pin(3, 1)

# set pin 4 LOW

pcf.pin(4, 0)

# toggle pin 5

pcf.toggle(5)

# set all pins at once with 8-bit int

pcf.port = 0xFF

# read all pins at once as 8-bit int

pcf.port

# returns 255 (0xFF)

```

For more detailed examples, see [examples](/examples).

If you mip installed them above, you can run them like so:

```python

import pcf8574.examples.basic

```

#### Pins

Pin  | Type | Description

:---:|:----:|:----------------------------------------

A0   | I    | Address select 1, connect to VCC or GND

A1   | I    | Address select 2, connect to VCC or GND

A2   | I    | Address select 3, connect to VCC or GND

INT  | O    | Interrupt output, open drain, active LOW

P00  | I/O  | Port A, Pin 0

P01  | I/O  | Port A, Pin 1

P02  | I/O  | Port A, Pin 2

P03  | I/O  | Port A, Pin 3

P04  | I/O  | Port A, Pin 4

P05  | I/O  | Port A, Pin 5

P06  | I/O  | Port A, Pin 6

P07  | I/O  | Port A, Pin 7

SDA  | I/O  | I2C Serial Data, needs pull-up

SCL  | I    | I2C Serial Clock, needs pull-up

GND  | PWR  | Ground

VCC  | PWR  | Supply voltage 3.3-5V

## Methods

Construct with a reference to I2C and set the device address.

Valid address range 0x20-0x27.

If are you not sure what it is, run an `i2c.scan()`.

See below for address selection.

```python

__init__(i2c, address=0x20)

```

Scans the I2C bus for the provided address and returns True if a device is present

otherwise raises an OSError.

```python

check()

```

Method for getting or setting a single pin.

If no value is provided, the port will be read and value of specified pin returned.

If a value is provided, the port will be updated and device written to.

The port is written to after each call. If you intend to toggle many pins at once, use the

port property instead. See below.

Valid pin range 0-7.

```python

pin(pin, value=None)

```

Method for flipping the value of a single pin.

Valid pin range 0-7.

```python

toggle(pin)

```

Private method for checking the supplied pin number is within the valid range.

```python

_validate_pin()

```

Private method for loading _port from the device.

```python

_read()

```

Private method for sending _port to the device.

```python

_write()

```

## Properties

Getter reads the port from the device and returns a 8-bit integer.

```python

port

```

Setter writes an 8-bit integer representing the port to the device.

If you are setting multiple pins at once, use this instead of the pin() method as

this writes the entire 8-bit port to the device once, rather than 8 separate writes.

```python

port = 0xFF

```

## Ports

* P00-P07 - Port A

This chip only has one port (8 pins). If you need more pins, the

[PCF8575](https://github.com/mcauser/micropython-pcf8575) has two ports (16 pins).

## Interrupts

* INT - Active LOW

## I2C Interface

If you are using a module, most contain 10k pull-ups on the SCL and SDA lines.

If you are using the PCF8574 chip directly, you'll need to add your own.

### I2C Address

The chip supports I2C addresses 0x20-0x27 and is customisable using address pins A0, A1, A2

A0  | A1  | A2  | I2C Address

----|-----|-----|------------

GND | GND | GND | 0x20 (default)

3V3 | GND | GND | 0x21

GND | 3V3 | GND | 0x22

3V3 | 3V3 | GND | 0x23

GND | GND | 3V3 | 0x24

3V3 | GND | 3V3 | 0x25

GND | 3V3 | 3V3 | 0x26

3V3 | 3V3 | 3V3 | 0x27

## Parts

* [PCF8574 blue chainable board](https://s.click.aliexpress.com/e/_DdzV1ZR)

* [PCF8574 blue chainable board](https://s.click.aliexpress.com/e/_DlQkWZj)

* [PCF8574 red board DIP switch](https://s.click.aliexpress.com/e/_DevQFrx)

* [PCF8574 red board DIP switch](https://s.click.aliexpress.com/e/_Dmeylnb)

* [PCF8574 purple board](https://s.click.aliexpress.com/e/_DlcJB2t)

* [PCF8574 as 1602 LCD backpack](https://s.click.aliexpress.com/e/_DlcJB2t)

* [PCF8574 10x DIP-16](https://s.click.aliexpress.com/e/_Dn3xoYh)

* [PCF8574 5x SOP-16](https://s.click.aliexpress.com/e/_DC1lqxn)

* [TinyPICO](https://www.tinypico.com/)

## Connections

### TinyPICO ESP32

```python

from machine import SoftI2C, Pin

i2c = SoftI2C(scl=Pin(22), sda=Pin(21))

from machine import I2C, Pin

i2c = I2C(0)

```

PCF8574 Module | TinyPICO (ESP32)

-------------- | ----------------

SDA            | 21 (SDA)

SCL            | 22 (SCL)

VCC            | 3V3

GND            | GND

INT (optional) | 4

## Links

* [micropython.org](http://micropython.org)

* [PCF8574 datasheet](docs/pcf8574.pdf)

* [TinyPICO Getting Started](https://www.tinypico.com/gettingstarted)

## License

Licensed under the [MIT License](http://opensource.org/licenses/MIT).

Copyright (c) 2019 Mike Causer