Overview

The USB interface provides two features to the AT32UC3L-EK kit:

• USB communication

• Power supply (see Section Power Supply for a description of that feature)

The USB controller is the AT32UC3B1256.

The AT32UC3B1256 comes pre-loaded with several firmware components:

• A USB DFU boot loader [accessible upon power up when the J12 header is closed (see Figure 2, for the location of the J12 header)] to re-program the AT32UC3B1256

• A USB CDC-USART bridge (a USB CDC virtual com port) where every data character received from the USB is sent to the AT32UC3L064's USART3, and every character received from the AT32UC3L064's USART3 is sent to the USB

• A HID QTouch Debug firmware acting as a USB HID-USART bridge between AVR QTouch Studio (Reference Materials) and the AT32UC3L064's USART3

• A tiny boot selector allowing the user to choose (using the USB MODE pushbutton) upon power up between running the virtual com port firmware or the HID QTouch Debug firmware. By default the HID QTouch Debug firmware will be running. See also Reference Materials.

The source code of this firmware is available in the AVR Software Framework (Reference Materials).

The user interface of the USB interface block is made of:

• Two LEDs, D12 and D13, [with the default firmware (except the USB DFU boot loader) these LEDs are blinking, depending on the activity over the USB]

• The USB MODE pushbutton on the PCB. With the default pre-loaded firmware, this button is used at power up to choose between the virtual com port firmware or the HID QTouch Debug firmware (see Configuration and Test Points for the AT32UC3B1256 default firmware configuration).

The AT32UC3B256 can be programmed:

• Through the JTAG interface J13 header (see Figure Figure 3 for the location of the J13 header)

• Through the USB DFU boot loader running on the AT32UC3B, accessible upon power up when the J12 header is closed

The AT32UC3B1256 is connected to the AT32UC3L064's USART3 TX and RX pins.