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PCF8574T I/O board


The PCF8574T is an I2C I/O expander chip and is obtainable from China on simple boards.

The chip has an open-drain port. This means that it depends on a pull-up to generate the high voltage output and when in this state it can also be used as an input. Setting a pin to zero pulls the pin low and this is the open-drain output state.

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