8 Channel Capacitive Touch Sensor with 2 LED Drivers
Datasheet
3.4
I2C Protocols
The CAP1128 supports I2C Block Write and Block Read.
The protocols listed below use the convention in Table 3.2.
3.4.1
Block Write
The Block Write is used to write multiple data bytes to a group of contiguous registers as shown in
Table 3.7.
APPLICATION NOTE: When using the Block Write protocol, the internal address pointer will be automatically
incremented after every data byte is received. It will wrap from FFh to 00h.
Table 3.7 Block Write Protocol
SLAVE
ADDRESS
REGISTER
ADDRESS
REGISTER
DATA
START
WR
ACK
ACK
ACK
1 ->0
YYYY_YYY
0
0
XXh
0
XXh
0
REGISTER
DATA
REGISTER
DATA
REGISTER
DATA
ACK
ACK
. . .
ACK
STOP
XXh
0
XXh
0
. . .
XXh
0
0 -> 1
3.4.2
Block Read
The Block Read is used to read multiple data bytes from a group of contiguous registers as shown in
Table 3.8.
APPLICATION NOTE: When using the Block Read protocol, the internal address pointer will be automatically
incremented after every data byte is received. It will wrap from FFh to 00h.
Table 3.8 Block Read Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
START
SLAVE
ADDRESS
RD
ACK
REGISTER
DATA
1->0
YYYY_YYY
0
0
XXh
0
1 ->0
YYYY_YYY
1
0
XXh
ACK
REGISTER
DATA
ACK
REGISTER
DATA
ACK
REGISTER
DATA
ACK
. . .
REGISTER
DATA
NACK
STOP
0
XXh
0
XXh
0
XXh
0
. . .
XXh
1
0 -> 1
3.5
SPI Interface
The SMBus has a predefined packet structure, the SPI does not. The SPI Bus can operate in two
modes of operation, normal 4-wire mode and bi-directional 3-wire mode. All SPI commands consist of
8-bit packets sent to a specific slave device (identified by the CS pin).
The SPI bus will latch data on the rising edge of the clock and the clock and data both idle high.
All commands are supported via both operating modes. The supported commands are: Reset Serial
interface, set address pointer, write command and read command. Note that all other codes received
during the command phase are ignored and have no effect on the operation of the device.
SMSC CAP1128
Revision 1.32 (01-05-12)
DATA2S1HEET
SMSC [ SMSC CORPORATION ]
