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AT42QT1110-MU

11-key QTouch® Touch Sensor IC

Atmel Corporation 

When the QT1110 is expecting a CRC byte, it returns (on MISO) the calculated CRC byte which it expects to

receive. This is sent simultaneously with the QT1110 receiving the CRC byte from the master (that is, during the

same byte exchange). This allows both devices to confirm that the data was sent correctly.

All data returned by the QT1110 is also be followed by a CRC byte, allowing the master to confirm the integrity of the

data transmission.

4.1.4 SPI Commands

There are three types of communication between the SPI master and the QT1110:

 Control commands (see Section 5. on page 22)

 To send control instructions to the QT1110

 Report requests (see Section 6. on page 24)

 To reading status information from the QT1110

 Setup commands (see Section 7. on page 28)

 To set configuration options (“Set” instructions)

 To read configuration options (“Get” instructions)

Additionally the NULL command (0x00) is transmitted by the host device as it is receiving data from the QT1110.

4.1.4.1 Control Commands

A control command is an instruction sent to the QT1110 that controls operations of the device, and for which no

response is required. Examples of control commands are: Reset, Calibrate, Send Setups.

With the exception of Send Setups, control commands normally require a single byte exchange, unless CRC

checking is enabled, in which case a second byte must be transmitted by the host with the calculated CRC of the

command byte.

Figure 4-1. Sleep Command – CRC Disabled

Host (Sends on MOSI)

Device (Responds on MISO)

Command: 0x05

Response: 0x55 (“Idle” – Fresh Command)

Simultaneous

Transmission

Figure 4-2. Sleep Command – CRC Enabled

Host (Sends on MOSI)

Device (Responds on MISO)

Command: 0x05

Response: 0x55 (“Idle” – Fresh Command)

Simultaneous

Transmission

Command CRC: 0x3F

Response: 0x3F (Expected Command CRC)

AT42QT1110-MU / AT42QT1110-AU [DATASHEET]

11

9520J–AT42–05/2013

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