Sensors & I/O

`import pcf8574`

The pcf8574 module controls PCF8574 and PCF8574A-compatible 8-bit GPIO expanders over I2C. The chip uses quasi-bidirectional pins, so there is no direction register: writing 0 drives a pin low, and writing 1 releases it high so it can be read as an input or used as a weak high output.

Quick example

import pcf8574

expander = pcf8574.PCF8574(sda=21, scl=22, address=0x20)

expander.low(0)
expander.high(1)

expander.input(2)
if expander.read_pin(2):
    print("pin is high")

print(expander.state())

import`pcf8574`

PCF8574 I2C GPIO expander module.

API 30 available

`pcf8574.PCF8574(sda: int, scl: int, address: int = None, frequency: int = None, port: int = None, initial: int = None) -> pcf8574_expander`

Create and initialize an independent PCF8574 GPIO expander.

Use one PCF8574 object for each physical expander. Multiple expanders can share one I2C bus when each chip has a unique address.

Parameters

Name	Type	Pass as	Required	Description
`sda`	`int`	positional or keyword	Yes	GPIO pin used for I2C SDA.
`scl`	`int`	positional or keyword	Yes	GPIO pin used for I2C SCL.
`address`	`int`	positional or keyword	No	Optional I2C address. PCF8574 commonly uses 0x20 through 0x27. PCF8574A commonly uses 0x38 through 0x3f. Defaults to 0x20.
`frequency`	`int`	positional or keyword	No	Optional I2C bus speed in hertz. Defaults to 100000.
`port`	`int`	positional or keyword	No	Optional ESP-IDF I2C port number. Defaults to 0.
`initial`	`int`	positional or keyword	No	Optional 8-bit latch value written during initialization. Defaults to 0xff, which releases all pins high.

Returns

pcf8574_expander pcf8574_expander object.

`pcf8574.PCF8574().write(value) -> bool`

Write this expander's full 8-bit output latch.

Parameters

Name	Type	Pass as	Required	Description
`value`	`any`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().read() -> int`

Read this expander's current 8-bit pin state.

`pcf8574.PCF8574().state() -> dict`

Read this expander's pins and latch as a dict.

`pcf8574.PCF8574().write_pin(pin, value) -> bool`

Write one pin by updating this expander's latch.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Required value.
`value`	`any`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().read_pin(pin) -> bool`

Read one pin from this expander.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().high(pin) -> bool`

Release one pin high.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().low(pin) -> bool`

Drive one pin low.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().input(pin) -> bool`

Release one pin so it can be used as an input.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().toggle(pin) -> bool`

Toggle one latch bit.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().set_mask(mask) -> bool`

Set latch bits using a mask.

Parameters

Name	Type	Pass as	Required	Description
`mask`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().clear_mask(mask) -> bool`

Clear latch bits using a mask.

Parameters

Name	Type	Pass as	Required	Description
`mask`	`int`	positional or keyword	Yes	Required value.

`pcf8574.PCF8574().reset() -> bool`

Release all pins high.

`pcf8574.PCF8574().info() -> dict`

Return I2C settings and current latch state for this expander.

`pcf8574.PCF8574().close() -> bool`

Release this PCF8574 handle.

`pcf8574.PCF8574().Example`

expander = pcf8574.PCF8574(sda=21, scl=22, address=0x20) expander.low(0) print(expander.state())

`pcf8574.begin(sda: int, scl: int, address: int = None, frequency: int = None, port: int = None, initial: int = None) -> bool`

Legacy: initialize the module-level default PCF8574 expander.

Prefer ``expander = pcf8574.PCF8574(...)`` for new projects. The legacy wrapper keeps older singleton-style scripts working.

Parameters

Name	Type	Pass as	Required	Description
`sda`	`int`	positional or keyword	Yes	GPIO pin used for I2C SDA.
`scl`	`int`	positional or keyword	Yes	GPIO pin used for I2C SCL.
`address`	`int`	positional or keyword	No	Optional I2C address. PCF8574 commonly uses 0x20 through 0x27. PCF8574A commonly uses 0x38 through 0x3f. Defaults to 0x20.
`frequency`	`int`	positional or keyword	No	Optional I2C bus speed in hertz. Defaults to 100000.
`port`	`int`	positional or keyword	No	Optional ESP-IDF I2C port number. Defaults to 0.
`initial`	`int`	positional or keyword	No	Optional 8-bit byte value written to the output latch during initialization. Defaults to 0xff, which releases all pins high.

Returns

bool True when the I2C bus is ready and the initial latch value is accepted.

`pcf8574.write(value: int) -> bool`

Write the full 8-bit output latch.

Parameters

Name	Type	Pass as	Required	Description
`value`	`int`	positional or keyword	Yes	8-bit byte value from 0 through 255. A 0 bit drives the matching pin low. A 1 bit releases it high.

Returns

bool True when the expander acknowledges the write.

`pcf8574.read() -> int`

Read the current 8-bit pin state.

Returns

int Integer pin state from 0 through 255.

`pcf8574.state() -> dict`

Read the current pin state as a dict.

Returns

dict Dict with ``ok``, ``value``, ``latch``, ``address``, and boolean ``p0`` through ``p7`` fields.

`pcf8574.write_pin(pin: int, value: bool) -> bool`

Write one pin by updating the module's output latch.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Pin number from 0 through 7.
`value`	`bool`	positional or keyword	Yes	Boolean pin value. False drives the pin low. True releases it high.

Returns

bool True when the updated latch is written.

`pcf8574.read_pin(pin: int) -> bool`

Read one pin.

For a pin used as input, call ``input(pin)`` first so the pin is released high before reading the external state.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Pin number from 0 through 7.

Returns

bool Boolean pin state.

`pcf8574.high(pin: int) -> bool`

Release one pin high.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Pin number from 0 through 7.

Returns

bool True when the updated latch is written.

`pcf8574.low(pin: int) -> bool`

Drive one pin low.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Pin number from 0 through 7.

Returns

bool True when the updated latch is written.

`pcf8574.input(pin: int) -> bool`

Release one pin so it can be used as an input.

The PCF8574 has quasi-bidirectional pins, not direction registers. This method writes a 1 to the selected latch bit.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Pin number from 0 through 7.

Returns

bool True when the pin is released high.

`pcf8574.toggle(pin: int) -> bool`

Toggle one latch bit.

Parameters

Name	Type	Pass as	Required	Description
`pin`	`int`	positional or keyword	Yes	Pin number from 0 through 7.

Returns

bool True when the updated latch is written.

`pcf8574.set_mask(mask: int) -> bool`

Set latch bits using a mask.

Parameters

Name	Type	Pass as	Required	Description
`mask`	`int`	positional or keyword	Yes	8-bit byte value. Bits set to 1 in the mask are set high in the latch.

Returns

bool True when the updated latch is written.

`pcf8574.clear_mask(mask: int) -> bool`

Clear latch bits using a mask.

Parameters

Name	Type	Pass as	Required	Description
`mask`	`int`	positional or keyword	Yes	8-bit byte value. Bits set to 1 in the mask are driven low in the latch.

Returns

bool True when the updated latch is written.

`pcf8574.reset() -> bool`

Release all pins high.

Returns

bool True when 0xff is written to the latch.

`pcf8574.info() -> dict`

Return PCF8574 module state.

Returns

dict Dict with initialization state, I2C pins, address, frequency, port, and current output latch value.

pcf8574

import pcf8574

Quick example

importpcf8574

pcf8574.PCF8574(sda: int, scl: int, address: int = None, frequency: int = None, port: int = None, initial: int = None) -> pcf8574_expander

pcf8574.PCF8574().write(value) -> bool

pcf8574.PCF8574().read() -> int

pcf8574.PCF8574().state() -> dict

pcf8574.PCF8574().write_pin(pin, value) -> bool

pcf8574.PCF8574().read_pin(pin) -> bool

pcf8574.PCF8574().high(pin) -> bool

pcf8574.PCF8574().low(pin) -> bool

pcf8574.PCF8574().input(pin) -> bool

pcf8574.PCF8574().toggle(pin) -> bool

pcf8574.PCF8574().set_mask(mask) -> bool

pcf8574.PCF8574().clear_mask(mask) -> bool

pcf8574.PCF8574().reset() -> bool

pcf8574.PCF8574().info() -> dict

pcf8574.PCF8574().close() -> bool

pcf8574.PCF8574().Example

pcf8574.begin(sda: int, scl: int, address: int = None, frequency: int = None, port: int = None, initial: int = None) -> bool

pcf8574.write(value: int) -> bool

pcf8574.read() -> int

pcf8574.state() -> dict

pcf8574.write_pin(pin: int, value: bool) -> bool

pcf8574.read_pin(pin: int) -> bool

pcf8574.high(pin: int) -> bool

pcf8574.low(pin: int) -> bool

pcf8574.input(pin: int) -> bool

pcf8574.toggle(pin: int) -> bool

pcf8574.set_mask(mask: int) -> bool

pcf8574.clear_mask(mask: int) -> bool

pcf8574.reset() -> bool

pcf8574.info() -> dict

`import pcf8574`

import`pcf8574`

`pcf8574.PCF8574(sda: int, scl: int, address: int = None, frequency: int = None, port: int = None, initial: int = None) -> pcf8574_expander`

`pcf8574.PCF8574().write(value) -> bool`

`pcf8574.PCF8574().read() -> int`

`pcf8574.PCF8574().state() -> dict`

`pcf8574.PCF8574().write_pin(pin, value) -> bool`

`pcf8574.PCF8574().read_pin(pin) -> bool`

`pcf8574.PCF8574().high(pin) -> bool`

`pcf8574.PCF8574().low(pin) -> bool`

`pcf8574.PCF8574().input(pin) -> bool`

`pcf8574.PCF8574().toggle(pin) -> bool`

`pcf8574.PCF8574().set_mask(mask) -> bool`

`pcf8574.PCF8574().clear_mask(mask) -> bool`

`pcf8574.PCF8574().reset() -> bool`

`pcf8574.PCF8574().info() -> dict`

`pcf8574.PCF8574().close() -> bool`

`pcf8574.PCF8574().Example`

`pcf8574.begin(sda: int, scl: int, address: int = None, frequency: int = None, port: int = None, initial: int = None) -> bool`

`pcf8574.write(value: int) -> bool`

`pcf8574.read() -> int`

`pcf8574.state() -> dict`

`pcf8574.write_pin(pin: int, value: bool) -> bool`

`pcf8574.read_pin(pin: int) -> bool`

`pcf8574.high(pin: int) -> bool`

`pcf8574.low(pin: int) -> bool`

`pcf8574.input(pin: int) -> bool`

`pcf8574.toggle(pin: int) -> bool`

`pcf8574.set_mask(mask: int) -> bool`

`pcf8574.clear_mask(mask: int) -> bool`

`pcf8574.reset() -> bool`

`pcf8574.info() -> dict`