Datasheet

8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Revision 1.32 (01-05-12) 26 SMSC CAP1188
DATASHEET
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 CAP1188 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.
Figure 3.6 SPI Write Command - Normal Mode
Figure 3.7 SPI Read Command - Normal Mode
Master SPDOUT
SPI_MOSI
Data to Write
SPI_CS#
SPI_CLK
Write Command – 7Eh
Unknown, Invalid Data Old Data at Current Address Pointer
SPI_MISO
Master Drives
Slave Drives
1. Data written at current
address pointer
2. Address pointer incremented
Master SPDOUT
SPI_MOSI
Master Drives Slave Drives
SPI_CLK
First Read Command – 7Fh
SPI_CS#
Invalid, Unknown Data *
SPI_MISO
‘0’ ‘1’ ‘1’ ‘1’ ‘1’ ‘1’ ‘1’ ‘1’
Subsequent Read
Commands – 7F
Data at Current Address Pointer
Address Pointer
Incremented **
‘0’ ‘1’ ‘1’ ‘1’ ‘1’ ‘1’ ‘1’ ‘1’
* 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