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AR1100 RESISTIVE USB AND RS-232 TOUCH SCREEN CONTROLLER

DS41606B-page 14  2011 Microchip Technology Inc.

4.1.3 USB MODE

The USB can enumerate as one of three ‘devices’ (or

device types) identified by a byte in EEPROM. See

Table 4-1.

The HID-MOUSE and HID-DIGITIZER types are

recognized by many host operating systems and will

provide cursor movement with a touch.

The HID-GENERIC type is a proprietary style, which

would require a custom software driver to support.

The controller defaults to the HID-MOUSE device type,

unless it is commanded to enumerate as one of the

other supported types.

Once enumerated, the USB device can be

signaled/commanded to re-enumerate as the same

device or to one of the other two. In processing the

command, the AR1100 writes the desired USB device

type to EEPROM prior to detaching from the bus and

executing a Reset. The SET_FEATURE control transfer

or a WRITE standard data transfer (via the Interrupt

end point) is used to convey the command (described

in Section 5.0, Commands).

4.2 Data Protocol

Data protocol utilizes multi-byte packet transfers in two

categories/formats:

1. Touch reports

2. Command packets

4.2.1 TOUCH REPORTS

Touch reports always originate from the AR1100 and

are transmitted in response to touch detection. The

format of the touch report is mode-dependent.

The measurement resolution for touch coordinates is

10-bit. The measured values are shifted (multiplied by

4) and reported in a 12-bit format. In the reporting

protocol, the Least Significant coordinate bits X1:X0

and Y1:Y0 will be zeros. The resulting full-scale range

for reported touch coordinates is 0 to 4095.

4.2.1.1 Mode: UART, HID-GENERIC

The ‘standard’, 5-byte touch report is formatted as in

Table 4-2:

TABLE 4-1: USB IDs

NAME DESC CLASS

VENDOR

PRODUCT

SPEED

HID-GENERIC Proprietary (AR1000-style) HID x04D8 x0C01 FULL

HID-MOUSE Mouse, absolute coordinates 0-4095 HID x04D8 x0C02 FULL

HID-DIGITIZER Single-input digitizer HID x04D8 x0C03 FULL

Note: The HID-MOUSE requires SET_FEATURE

and does not support a data WRITE.