Atmel AVR4901 Installation and operating instructions

Atmel AVR4901: ASF - USB Vendor Class

Application

Features

• USB 2.0 compliance

- Chapter 9 compliance

- Full Speed (12Mbit/s), High Speed (480Mbit/s) data rates

• Control, Bulk, Isochronous and Interrupt transfer types

• Small stack size frees space for main application

• Remote wakeup support

• USB bus powered support

• Real time (O.S. compliance, interrupt driven)

• Support 8-bit and 32-bit AVR®

1 Introduction

The aim of this document is to provide an easy way to integrate a USB vendor

class application on a new or existing project.

8-/32-bit Atmel

Microcontrollers

Application Note

Rev. 8481A-AVR-01/12

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2 Abbreviations

ASF: AVR Software Framework

CD: Composite Device: a USB device with more than one interface

CDC: Communication Device Class

FS: USB Full Speed

HID: Human Interface Device

HS: USB High Speed

LS: USB Low Speed

MSC: Mass Storage Class

UDC: USB device Controller

UDD: USB device Descriptor

UDI: USB device Interface

USB: Universal Serial Bus

SOF: Start of Frame

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3 Overview

This document includes six sections for all types of requirements when building a

USB device vendor application:

•Vendor class Specification

Provides information to help users with the vendor class specification and when

they need such solution

•Quick start

Describes how to start a ready to use vendor class device example

•Example description

Describes a vendor class device example

•Building a USB device vendor

Describes how to add a USB device vendor interface in a project

•Building a USB vendor class application

Describes how to add a USB vendor class application

•Vendor class in a USB composite device

Describes how to integrate a vendor class interface in a composite device project

For all these sections, it is recommended to know the main modules organization of a

vendor class application:

•User Application

•USB device Interface VENDOR (UDI-VENDOR)

•USB device Controller (UDC)

•USB device Driver (UDD)

For more advanced information concerning the USB stack implementation, please

refer to the Atmel®AVR4900 ASF USB Device stack application note.

Figure 3-1. USB vendor class solution architecture.

NOTE The USB device stack is available in the ASF in the common/services/usb directory.

UDD

UDC UDI – VENDOR

Application

USB Device stack from the ASF

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4 Vendor class specification

The development of a vendor class can be required when the existing class

(http://www.usb.org/developers/defined_class) does not correspond to the user

specification.

Before starting a vendor class specification, check in Table 4-1 that the native USB

classes are not applicable for your USB application.

Table 4-1. Analysis of native classes.

Class PROS. CONS.

HID

•Native driver

•USB Low Speed mode support

•Suitable for controlling or

monitoring an application

•Interrupt endpoint:

olow and full speed

64KB/s

ohigh speed 2.93MB/s

CDC

•High transfer rate

•Simple Host application

(terminal)

•Easy migration for USART based

applications

•Need of *.inf file under Windows®

•Driver not WHQL certified

MSC •Native driver •SCSI protocol adapted only for

mass storage

AUDIO

•Native driver

•Interesting to record or send data

stream

•No handshake data transfer

(isochronous)

When building a vendor class, the main important thing to specify is the transfer

modes used by endpoints.

These can be chosen based on the description given in Table 4-2.

Table 4-2. Endpoint type description.

Endpoint

type

Description Use case

Control

•Low transfer rate

•No need of new endpoint which

can reduce application footprint

•Configuration of the device

Interrupt •Very low transfer

•Frequency guaranteed

•Real time constraints and low

bandwidth transfer

Bulk •High transfer rate

•Transfer guaranteed (ACK)

•Large amount of data transfer

Isochronous •Very High transfer rate

•Transfer not guaranteed

•Streaming application

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5 Quick start

The USB device vendor examples are available in Atmel AVR Studio®5 and ASF.

Hereunder is the procedure to start a USB device vendor class example quickly:

1. Connect the board (for example the Atmel AVR XMEGA®-A3BU Xplained kit)

to the PC using the USB cable.

2. Connect the Atmel debugger (hereafter the JTAGICE3) to program the

device.

Figure 5-1 Board connection.

3. Start AVR Studio 5 and click on “New Example Project from ASF”.

In the New Example Project’s list, select “USB Device Vendor Class Example”

based on the board you are using. The filter list can be used to find the example

quickly.

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4. Compile, load and execute.

The project does not require any modification and only needs to be compiled, loaded

and ran. Connect the Atmel debugger supported by the board and press F5.

When running the application for the first time a Found New Hardware Wizard pops

up as showing below, select “No, not this time” and click on “Next”:

5. Load the driver using the inf file.

NOTE Since the USB vendor class is not supported by any native driver, user needs to

provide a proprietary driver or use a third party solution.

For this example, an open source solution “libusb” is used to support this device. An

inf file was generated by the libusb tool. Point to the folder avr4901/driver/ to install

the driver.

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Once the device is correctly installed, lunch the avr_vendor_class_example.exe from

the folder avr4901/tool/. This program will perform a loopback in all endpoints. A

status is displayed to show the correct execution of the application:

5.1 Hardware behavior

During the application execution the hardware (used board) should behave as below:

•A LED is on when USB device is in active mode and is off in SUSPEND mode

•A LED blinks showing that vendor class interface is enabled by the USB Host

•A LED is on when the loopback is running

Figure 5-2. Example with the Atmel XMEGA-A3BU Xplained board.

LED on when

USB is active

LED blinks showing

Vendor interface is

enabled

LED blinks showing

loopback is running

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The user interface description (specific to the board) is defined at the end of ui.c

source file. This file is available within the “Solution Explorer” under

“common/services/usb/class/vendor/device/example/part_number_board/”.

Figure 5-3 ui.c file location.

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6 Example description

6.1 Example content

The ASF provides a USB device vendor class example for various Atmel AVR

products. All these examples share common files and implement the same

application.

The Table 6-1 introduces a summary of the main files included in the USB device

vendor example. These files are associated to the modules described in Figure 3-1.

Table 6-1. USB device VENDOR example files.

Modules Files ASF paths Description

Application main.c

ui.c

conf_usb.h

Examples folder

Main loop.

Set up hardware switches and LEDs to show

operations.

USB device configuration.

udi_vendor.c/h common/services/usb/class/vendor/device/ Vendor class implementation

UDI VENDOR

udi_vendor_desc.c

udi_vendor_conf.h common/services/usb/class/vendor/device/

USB Descriptors for an USB device with

vendor interface (not applicable for USB

composite device)

udc.c/h

udc_desc.h

udi.h

udd.h

common/services/usb/udc/ USB device Core

UDC

usb_protocol.h

usb_atmel.h common/services/usb/ USB Protocol constants

UDD usbb_device.c/h

usbc_device.c/h

usb_device.c/h

avr32/drivers/usbb/

avr32/drivers/usbc/

xmega/drivers/usb/

USB Drivers

6.2 Example behavior

The main.c and ui.c files implement the user interface vendor application. It is

based on three steps:

1. Start USB device:

udc_start();

udc_attach(); // Must be called when the USB cable is plugged

// Cable plugged is detected via VBus events

2. Wait the enable of vendor interface via call-back and enable the loopback

process:

UDI_VENDOR_ENABLE_EXT() // Interface enabled callback

The callback calls:

- udi_vendor_bulk_out_run()// Enable transfer on interrupt OUT endpoint

- udi_vendor_interrupt_out_run()//Enable transfer on interrupt OUT endpoint

- udi_vendor_iso_out_run() //Enable transfer on isochronous OUT endpoint

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3. Perform loopback in all endpoints (Control, Interrupt, Bulk and Isochronous):

// When a OUT data is received, then send this data on IN

void main_vendor_int_out_received(udd_ep_status_t status,

iram_size_t nb_transfered)

{

if (UDD_EP_TRANSFER_OK != status) {

return; // Tranfert aborted, then stop loopback

}

ui_loop_back_state(true);

// Send on IN endpoint the data received on endpoint OUT

udi_vendor_interrupt_in_run(

main_buf_loopback,

nb_transfered,

main_vendor_int_in_received);

}

// When a IN data has been sent, then the OUT transfer is enabled again

void main_vendor_int_in_received(udd_ep_status_t status,

iram_size_t nb_transfered)

{

if (UDD_EP_TRANSFER_OK != status) {

return; // Tranfert aborted, then stop loopback

}

ui_loop_back_state(false);

// Wait a full buffer

udi_vendor_interrupt_out_run(

main_buf_loopback,

sizeof(main_buf_loopback),

main_vendor_int_out_received);

}

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