PCF8574A 8-bit I/O Expansion Modules - I2C interface

No matter how many ports an Arduino board has, they never seem to be enough for the cool new project you have in mind. Luckily there is a solution. The Arduino has both I2C and SPI pins, and there are a number of I2C and SPI GPIO chips, and modules built with those chips. One of the cheapest and most widely used one is the PCF8574/PCF8574A. On the positive side it is widely available and there are ready cheap modules with it. The down side is that it has only 8 channels. The good news is that you can connect multiple such modules on the same I2C channel.

Features

• Based on the I2C interface I/O expansion modules
• Two I/O can be extended to eight  (up to simultaneous use 8 PCF8574, expanded to 64 I/O)
• 2 supports I2C bus cascade (via pin, row seat docking methods can be used simultaneously multiple I2C modules)
• Compatible with Arduino and Raspberry Pi

Specifications

• Interface:  I2C
• Board Type: Pin or row seat
• I2C interface
• 8-bit parallel
• Size: 54*15mm
• Net Weight: 7g

Package Included

1 x PCF8574A I/O Expansion Modules

PCF8574A GPIO Module has Jumpers that can be used to specify the I2C address.

If you position each Jumper to the "-" side it will set to value Zero (Picture above) for the Address bit, and if you switch it to the "+" side, it will set for the Address bit.

The PCF8574 and PCF8574A have a different set of addresses.

 

The following example are the table of addresses based on the +/- settings of the jumpers:

A2	A1	A0
●	●	●	for PCF8574 (32), for PCF8574A (56)
●	●		for PCF8574 (33), for PCF8574A (57)
●		●	for PCF8574 (34), for PCF8574A (58)
●			for PCF8574 (35), for PCF8574A (59)
	●	●	for PCF8574 (36), for PCF8574A (60)
	●		for PCF8574 (37), for PCF8574A (61)
		●	for PCF8574 (38), for PCF8574A (62)
			for PCF8574 (39), for PCF8574A (63)