In this article we are discussing Embedded Interface – PCF8574 and PCF8574A I/O Expender.
The PCF8574 device provides general-purpose remote I/O expansion for most micro controllers
families by way of the I2C interface [serial clock(SCL), serial data (SDA)]. 8-bit 2.5- to 5.5-V I2C/SMBus I/O expander with interrupt
The device features an 8-bit quasi-bidirectional I/O port (P0–P7), including latched outputs with high current drive capability for directly driving LEDs. Each quasi-bidirectional I/O can be used as an input or output without the use of a data-direction control signal. At power on, the I/Os are high. In this mode,
only a current source to VCC is active.
Contents
Feature of PCF8574
- Two-wire i2c Bus Interface
- 8-Bit Parallel Bus Ex-panders
- Operating Voltage VCC -2.5v to 6v
- Up to 8 Addressed by three hardware-address pins
- Low standby current consumption 10mA maximum
- LED Driving (Latched output with high-current drive capability)
Typical Applications
- Fan Control
- LED Driver
- Cost-effective method to monitor several peripheral signals
- Temperature Sensor Monitoring
- 8-Bit Bidirectional expansion
PCF8574 I/O Expender Block Diagram
Functional Description of PCF8574
PCF8574 Applications
Multiple I/O Expender
Bi-Directional PCF8574 I/O Expender
High Current-Drive Load of PCF8574 PCF8574A I/O Expender
Difference b/w PCF8574 and PCF8574A ?
The main difference between the these ICs is the i2c address
- PCF8574 Address range (0x20 to 0x27 – up-to 8 device)
- PCF8574A Address range (0x38 to 0x3F – up-to 8 device)
Difference B/W Ti-PCF8574 and Philips PCF8574?
- Package 20 Pin TVSOP (23% smaller than 20 pin TSSOP)
- Package 20 Pin QFN Package (62% smaller than 20-pin TSSOP)
DataSheet
- https://www.nxp.com/documents/data_sheet/PCF8574.pdf (Philips)
- http://www.ti.com/lit/ds/symlink/pcf8574.pdf (Texas Instruments)
- http://www.ti.com/lit/ml/scyb031/scyb031.pdf
Useful Resource
- http://www.ti.com/product/PCF8574
- http://www.ti.com/product/PCF8574A
- https://primalcortex.wordpress.com/2015/08/21/nodemcu-and-i2c-how-to-start-and-using-the-pcf8574a-i2c-port-expander-on-esp-01-board
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