Paul Evans


Device::Chip::PCF8574 - chip driver for a PCF8574


This Device::Chip subclass provides specific communication to a NXP or Texas Instruments PCF8574 attached to a computer via an I²C adapter.

The reader is presumed to be familiar with the general operation of this chip; the documentation here will not attempt to explain or define chip-specific concepts or features, only the use of this module to access them.



The I²C address of the device. Can be specified in decimal, octal or hex with leading 0 or 0x prefixes.


The following methods documented with a trailing call to ->get return Future instances.


   $chip->write( $val )->get

Sets the value of the GPIO pins, as an 8-bit integer.

Pins set low will sink current suitable for signalling or driving an LED. Pins set high will source current via a weak current-source to act as a pull-up for an active-low input signal, such as a button.


   $val = $chip->read->get

Reads the current logic levels on the GPIO pins, returned as an 8-bit integer. Pins of interest as inputs should have previously been set to high level using the "write" method.


   $adapter = $chip->as_adapter

Returns a new object implementing the Device::Chip::Adapter interface which allows access to the GPIO pins of the chip as if it was a GPIO protocol adapter. The returned instance supports the following methods:

   $protocol = $adapter->make_protocol( 'GPIO' )



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