MXT1664T3-ABESSQTP datasheet(64/98 Pages) MICROCHIP

64 / 98 page

MXT1664T3 2.0

DS40002054A-page 64

 2018 Microchip Technology Inc.

12.0

GETTING STARTED WITH MXT1664T3

12.1

Establishing Contact

12.1.1

COMMUNICATION WITH THE HOST

The host can use any of the following interfaces to communicate with the device (See Section 7.0 “Host

Communications”):

•I2C interface (see Section 8.0 “I2C Communications”)

•HID-I2C interface (see Section 9.0 “HID-I2C Communications”)

• USB interface (see Section 10.0 “USB Communications”)

12.1.2

POWER-UP SEQUENCE

On power-up, the CHG line goes low to indicate that there is new data to be read from the device. If the CHG line does

not go low, there is a problem with the device.

Once the CHG line goes low, the host should attempt to read the first 7 bytes of memory from location 0x00 to establish

that the device is present and running following power-up.

A checksum check is performed on the configuration settings held in the non-volatile memory. If the checksum does not

match a stored copy of the last checksum, then this indicates that the settings have become corrupted. The host should

write a correct configuration to the device if the read checksum does not match the expected checksum, or if the

configuration error bit in the message data from the Command Processor T6 object is set.

12.2

Using the Object Protocol

The device has an object-based protocol that is used to communicate with the device. Typical communication includes

configuring the device, sending commands to the device, and receiving messages from the device.

The host must perform the following initialization so that it can communicate with the device:

Read the start positions of all the objects in the device from the Object Table and build up a list of these

addresses.

Use the Object Table to calculate the report IDs so that messages from the device can be correctly interpreted.

12.2.1

CLASSES OF OBJECTS

The mXT1664T3 contains the following classes of objects:

• Debug objects – provide a raw data output method for development and testing.

• General objects – required for global configuration, transmitting messages and receiving commands.

• Touch objects – operate on measured signals from the touch sensor and report touch data.

• Signal processing objects – process data from other objects (typically signal filtering operations).

• Support objects – provide additional functionality on the device.

12.2.2

OBJECT INSTANCES

TABLE 12-1:

OBJECTS ON THE MXT1664T3

Object

Description

Number of

Instances

Usage

Debug Objects

Diagnostic Debug T37

Allows access to diagnostic debug data to aid

development.

Debug commands only. No

configuration/tuning necessary.

Not for use in production.

General Objects

Message Processor T5

Handles the transmission of messages. This

object holds a message in its memory space

for the host to read.

No configuration necessary.

Command Processor T6

Performs a command when written to.

Commands include reset, calibrate and

backup settings.

No configuration necessary.

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