2
AVR069
8015B-AVR-02/06
2 USB Communication
The communication between the AVRISP mkII and the PC is done through its USB
interface. The USB interface utilizes two bulk endpoints; one IN and one OUT. The
USB descriptors can be found in chapter 6.2.
2.1 Packet Format
The PC sends commands to the AVRISP mkII, which responds with an answer. Each
command will generate an answer.
Both commands and answers can be larger than the maximum packet size for the
bulk endpoints, so a command or answer can be split into several IN/OUT packets. A
short packet indicates the end of a command or answer.
The commands and their respective answers are described in chapter 3.
2.2 USB Driver
In order to communicate with the AVRISP mkII, a driver must be installed on the host
computer. A driver can be written from scratch or by using a driver development kit.
AVR Studio 4 bundles a USB driver licensed from Jungo (
www.jungo.com). By
obtaining a license from Jungo, 3rd party software can access the same driver as
AVR Studio. The user can then use both AVR Studio and other tools without
changing drivers.
Note: Firmware upgrades for AVRISP mkII can only be uploaded with the dedicated upgrade
software bundled with AVR Studio. This requires that the driver supplied with AVR Studio to be
installed.
3 Commands
This section describes all commands that can be entered to the AVRISP mkII, and all
the possible responses that each command can give back to the host.
For all commands, the AVRISP mkII will return an answer with an answer ID that is
equal to the command ID. The first byte in a command is always the command ID, the
first byte in an answer is always the answer ID.
3.1 General Commands
3.1.1 CMD_SIGN_ON
This command returns a unique signature string for the AVRISP mkII with this
implementation of the protocol.
Table 3-1
. Command format
Field Size Value Description
Command ID 1 byte CMD_SIGN_ON Command id
