What is it?

This interface enables non-GPIO computers (like PC) to monitoring (monitoring contact status) or control (drive LED or relay opto board).

Also, the interface is useful when the available amount of GPIOs is insufficient or when you don't want to expose existing GPIOs to the outside (like Raspberry Pi).

This module allows up to 64 inputs or outputs via serial communication.

The module consists of an Arduino Nano that communicates with the PCF8575 (16x I/O port expander IC) via an I2C bus.

Up to 4 PCF8575 (4x16 = 64 I/O) can be connected by one Arduino.

Module can work as Monitoring or as Control mode. Working mode is selected by jumper "code select" on the PCB.

Module send message(s) only when some port is changed (Input monitoring mode). There is no constant polling and processing data. Very low(minimal) USB/Serial port load!

Why did you make it?

I needed more inputs/outputs and manipulate with them on the easy way! Also, needed 5V compatible output voltage for opto-relay board and avoid additional driver IC.

What makes it special?

• Universal usage via serial(USB) port.
• Same module can be used for input and output mode of operation, selected by jumper! No need to have/buy different products!
• Expandable up to 64 inputs/outputs!
• Screw terminal on PCB, don't need additional interconnection!
• Very low proccessing and USB load! Changes are send only when occurs!
• Also, input status can be reading by command at any time;(Monitoring mode),

User manual

User manual,node-red-contrib-PCF8575-extractor,examples and other details are in "Spec and Docs".

Extended PCB

Use this board to add 16 ports to the Basic PCB.

A maximum of 3 PCBs can be added to the Basic PCB, so the total I/O ports are 64.

What is included?

The PCBs are assembled and look like in the pictures. Wires, and montage spacers are not included. Debouncing capacitors behind screw terminals are optional and not included.