NXP GPIO Expander User Manual
GPIO Expander
Cost-effective, flexible options from
the I2C-bus leader
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NXP’s general-purpose input/output (GPIO) expanders are a simple, cost-effective way to monitor and control several peripheral
5.0V
signals. They make it easy for designers to add extra I/O to their design and thereby free up the microprocessor’s GPIO for other,
more important functions. NXP is the industry leader in serial-interface GPIO expanders, and offers a broad selection of costeffective, easy-to-use options.
I2C-Bus GPIO Expander Application Example
VDD
MASTER
CONTROLLER
GND
SDA
SCL
RST
INT
OE
VDD = 2.3V to 5.5V
10KΩ Ω Ω Ω
10K 10K
10K
SDA
SCL
RESET
INT
OE
AD2
AD1
AD0
VDD
PCA9698
GND
IO0_0
IO0_1
IO0_2
IO0_3
IO0_4
IO0_5
IO0_6
IO0_7
IO1_0
IO1_7
IO2_0
IO2_7
2KΩ
SUBSYSTEM 1
Temp. Sens or
INT
Switch
Switch
10KΩ
Switch
SUBSYSTEM 2
Coun ter
RST
10KΩ
10KΩ
24 L ED Matrix
Alp hanu mer ic
Keyp ad
SUBSYSTEM 3
Alar m Syst em
ALARM
5.0V
5.0V
SUBSYSTEM 4
Memor y
CS
I2C-bus address = 0100 000x
The I2C-bus allows easy two-line communication between two devices using a serial data line (SDA) and a serial clock line (SCL)
and, as a result, is a popular choice for computing, consumer electronics, communication, and industrial systems.
I2C-Bus Communication Protocol and Timing Diagram
SDA
MSB
LSB
R/W
RX-ACK
MSB
LSB
RX-ACK
SCL
Start
Condition
1
2
Address Transfer
From Master to Slave
3-6 7
8
Data
Direction Bit
9
1 2
Data Transfer From Master to Slave (Write)
or Slave to Master (Read)
3-7 8
9
Stop
Condition
NXP’s I2C-bus GPIO expanders support three operating modes for data transfer: Standard Mode, with data transfer rates from
0 kbps to 100 kbps, Fast Mode (Fm), with data transfer rates from 0 kbps to 400 kbps, and Fast-mode Plus (Fm+) with data rates
from 0 kbps to 1 Mbps. Since the newer Fm+ GPIO are backward compatible all the way back to Standard Mode, it’s easy to
expand existing designs without changing the bus master device.
Application Support
NXP supports its GPIO expanders with several evaluation modules
UART
LED
PCA9901
8-pin SPI
connector
SPI
9-pin I2C-2005
connector
9-pin I2C-2005
connector
and demo boards that can be used to develop software and
evaluate performance.
The I2C-bus Fm+ Development Kit and associated GPIO daughter
cards provide a quick way to learn about the devices and the
I2C-bus protocol. The cards are modular, so they increase design
flexibility while providing easy access to the expander’s I/O pins.
For more information, visit ics.nxp.com/support/tools/interface
connector
USB
power jack
LPCXpresso
socket
LPC1343
SPI
5 V
8-pin SPI
connector
LED Bank
PCA9955
PCA9665
Fm+
I
2
C-bus
16-pin
connector
10-pin connector
to target board
Fm+
I
2
C-bus
Fm+
I
2
C-bus
PCA9672
GPIO
9-pin I2C-2005
connector
5-pin bus-buffer
connector
5-pin bus-buffer
connector
5-pin bus-buffer
connector
9-pin I2C-2005
connector
9-pin I2C-2005
connector
5-pin bus-buffer
002aaf760
connector
9-pin I2C-2005
connector
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