PCF8574

class pcf8574.PCF8574(i2c, address, direction=None, state=None, inverted=None)

Class to control a PCF8574/A IC

Parameters:

  • i2c (I2C) – I2C peripheral

  • address (int) – Address of the PCF8574/A device

  • direction (str, optional) – Direction of pins

    String representation of each pin (1 input / 0 output)

    ‘10100110’ = input, output, input, output*2, input*2, output

  • state (str, optional) – Initial digital state of pins (physical),

    String representation of each pin (1 on / 0 off for output, 1 for input)

    ‘10101111’ = input, off, input, off, on, input*2, on

  • inverted (str, optional) – Inverted pins

    String representation of each pin (1 inverted / 0 non inverted)

    ‘11100011’ = inverted*3, non*3, inverted*2
Variables:
  • interrupt (int) – counter for interruption
  • changed_pins (bytearray) – bytearray of [pin/value] * 8 where pin is set to 1 when changed and value is the new value of the pin.
direction(pin)

Return the direction of a pin

Parameters:pin (int) – pin 0-7
Returns:1 for input, 0 for output
Return type:int
disable_int()

Disable interrupt

enable_int(pin)

Enable input interrupt

To get the changed pins, use the attribut changed_pins

Parameters:pin (int) – interrupt pin
input_pin(pin, invert=False)

Set pin(s) as input

Parameters:

  • pin (int or list) – pin 0-7

  • invert (bool, optional) – True inverted pin, False non inverted pin. Defaults to False.

    If a list of pins is given, invert applies to all pins
invert_pin(pin, invert=False)

Set a pin has inverted or not

Previous state is kept

Parameters:

  • pin (int or list) – pin 0-7

  • invert (bool, optional) – True inverted pin, False non inverted pin. Defaults to False.

    If a list of pins is given, invert applies to all pins
inverted(pin)

Return the inverted state of a pin

Parameters:pin (int) – pin 0-7
Returns:1 for inverted, 0 for non inverted
Return type:int
output_pin(pin, invert=False)

Set pin(s) as output

Parameters:

  • pin (int or list) – pin 0-7

  • invert (bool, optional) – True inverted pin, False non inverted pin. Defaults to False.

    If a list of pins is given, invert applies to all pins
read_pin(pin)

Read value of a pin

Parameters:pin (int) – pin 0-7
Returns:The pin value 0 or 1
Return type:int
reset_int()

Reset interrupt

Use this method after using the interrupt

write_pin(pin, value)

Write value to an output pin

Parameters:
  • pin (int) – pin 0-7
  • value (bool) – value to write