IO Expander

With the IO expander pcf8574 and pcf8575 you can add more GPIO relays and buttons to TerrariumPI. This IO expander does only support on/off actions. So it is not possible to use this IO expander with a DHT sensor. You cannot read out the extra GPIO ports.

Addressing

In order to use this IO expander, enter the following address in the GPIO relay or button address field.
pcf857<4/5>-<IO expander port>,<I2C Address>,[I2C Bus number]

Either use pcf8574 or pcf8575 to select the used IO expander.

<IO expander port> is mandatory and is a number from 0 till max ports - 1.

<I2C Address> is mandatory and specified here.

PCF8574

This is a 8 ports IO expander. The yellow on the image.

PCF8575

This is a 16 ports IO expander. The right blue board on the image.