Analog Devices EV-SC598-SOM, Manual

Page: 23 / 33

GPIO Register Register Address
GPIOA 0x12
GPIOB 0x13
•
By default, the Microchip MCP23018 GPIO signals function as input signals.
The signals must be programmed as output signals to override their default values. A zero is programmed into
the register to enable the signal as an output. The following table shows the Microchip register addresses.
IODIR Register IODIR Register Address
IODIRA 0x00
IODIRB 0x01
Each example in the Board Support Software (BSP) includes source files that program the soft switches, even if the
default settings are being used. The
README for each example identifies only the signals that are being changed
from their default values. The code that programs the soft switches is located in the SoftConfig_XXX.c file in
each example where XXX is the name of the baord.
The following tables ( I
2
C Hardware Address 0x21 and I
2
C Hardware Address 0x22 ) outline the default values for
each of the two Microchip MCP23018 devices.
Table 3-2: I
2
C Hardware Address 0x21
GPIO MCP23018 Register Address Default Value
GPIOA 0x12 0x02
GPIOB 0x13 0xC4
Table 3-3:
I
2
C Hardware Address 0x22
GPIO MCP23018 Register Address Default Value
GPIOA 0x12 0xE0
GPIOB 0x13 0xFF
The board schematic shows how the two Microchip GPIO expanders are connected to the board’s ICs.
Tables Output Signals of Microchip GPIO Expander (U24 Port A) and Output Signals of Microchip GPIO Expand-
er (U24 Port B) show the output signals of the Microchip GPIO expander ( U24 ), with a TWI address of
0100
001X
, where
X
represents the read or write bit. The signals that control an individual FET have an entry in the
FET column. The Component Connected column shows the board IC that is connected if the FET is enabled. The
Microchip (
U24
) is controlling the enable signal of a FET switch. Also note that if a particular functionality of the
processor signal is being used, it is in bold font in the Processor Signal column.
Software-Controlled Switches (SoftConfig)
EV-SC598-SOM
®
Manual
3–7