UCS81003 Evaluation Board User’s Guide
DS50002300A-page 22
2014 Microchip Technology Inc.
3.3
MCP2221 USB-TO-SMBUS BRIDGE
The MCP2221 is a USB-to-UART/I
2
C bridge that supports SMBus communication. It is
controlled through USB interface by the GUI running on the PC. It is the master device
on the SMBus/I2C bus. It is used to read and write the registers of the two devices
connected to the SMBus/I
2
C interface: UCS81003 and MCP23018 I/O expander.
3.4
MCP23018 I/O EXPANDER
MCP23018 is a 16-bit I/O Expander with open-drain outputs and I
2
C interface. Its I
2
C
address is configured to
0100_000(R/W)
, different than all possible addresses of the
UCS81003.
The I/O pins used in this application are configured as inputs. They are used to read
the logic state of the following UCS81003 pins: ALERT#, ADET#, PWR_EN, EM_EN,
M1, M2.
3.5
DIRECT SMBUS CONNECT OPTION
It is also possible to connect an external SMBus master to the UCS81003 Evaluation
Board. Remove the jumpers on J7 and connect the SMBus master to the header pins
that are linked directly to UCS81003 pins SMDATA/LATCH and SMCLK/S0. Note that
ground must be connected to one of the test point grounds or header pins on the EVB.
See
for header pins description.
FIGURE 3-1:
UCS81003-to-SMBus Bridge Jumpers.
USB bridge
SCL pin
SMCLK/S0
UCS81003
pin
USB bridge
SDA pin
SMDATA/LATCH
UCS81003
pin
Ground
