8 Channel Capacitive Touch Sensor with 2 LED Drivers
Datasheet
SPI_CS#
SPI_CLK
Master SPDOUT
Data to Write
Write Command – 7Eh
SPI_MOSI
SPI_MISO
Unknown, Invalid Data
Old Data at Current Address Pointer
Master Drives
Slave Drives
1. Data written at current
address pointer
2. Address pointer incremented
Figure 3.6 SPI Write Command - Normal Mode
3.6.4
Read Data
The Read Data protocol is used to read data from the device. During the normal mode of operation,
while the device is receiving data, the CAP1128 is simultaneously transmitting data to the host. For
the Set Address commands and the Write Data commands, this data may be invalid and it is
recommended that the Read Data command is used.
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MOSI
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
Subsequent Read
Commands – 7F
First Read Command – 7Fh
SPI_MISO
Invalid, Unknown Data *
Data at Current Address Pointer
Address Pointer
Incremented **
Master Drives
Slave Drives
* The first read command after any other command will return invalid data for the first
byte. Subsequent read commands will return the data at the Current Address Pointer
** The Address Pointer is incremented 8 clocks after the Read Command has been
received. Therefore continually sending Read Commands will result in each command
reporting new data. Once Read Commands have been finished, the last data byte will be
read during the next 8 clocks for any command
Figure 3.7 SPI Read Command - Normal Mode
Revision 1.32 (01-05-12)
SMSC CAP1128
DATA2S6HEET
SMSC [ SMSC CORPORATION ]
