AT90USBxxxx USB OTG Library - HID Demonstration

License

Use of this program is subject to Atmel's End User License Agreement.

Please read file license.txt for copyright notice.

Description

This embedded application source code illustrates how to implement a simple application using the USB OTG library. User must connect this board to another one that supports the OTG protocol, and that has the same firmware. At the time of writing, only STK525 and USBKEY are OTG compatible (but not totally compliant), and can be connected together. This application is customizable, please look at "conf_usb.h".

About the sample application

This package is compatible with STK525 and USBKEY, user has just to set the board name in TARGET_BOARD ("config.h"). Boards must be configured in SELF POWERED mode (external power source). The application uses both peripheral and host operating mode of the micro. This application is reserved to OTG demonstration, and may not run correctly when attached to a standard PC (non-OTG). Concept is simple : user has to press a button on the Peripheral board to toggle the LED state of the Host board. But USB OTG features the following possibilities : PERIPHERAL MODE (default if MiniB inserted at start up)

• press HWB button to send a SRP ; this work only in B-IDLE state (only if no Vbus detected)
• once connected to Host, press CENTER button (joystick) to toggle the LED state
• when connected as a peripheral, a LED should be continuously lighting to indicate this role

HOST MODE (default if MiniA inserted at start up)

• press HWB button to toggle Vbus ON/OFF ; this works in any state of A-DEVICE (even A-PERIPHERAL)
• if in A-HOST state, press CENTER button to initiate an HNP (and become A-PERIPHERAL)

MESSAGING FEATURE

• refer to "otg_user_task.c" and "otg_user_task.h" to learn about LED signification

Architecture

As illustrated in the figure below, the application entry point is located in the main.c file. The main function first performs the initialization of a scheduler module and then runs it in an infinite loop. The scheduler is a simple infinite loop calling all its tasks defined in the conf_scheduler.h file. No real time schedule is performed, when a task ends, the scheduler calls the next task defined in the configuration file (conf_scheduler.h).

The application is based on two different tasks:

• The usb_task() (usb_task.c associated source file), is the task performing the USB low level enumeration process in peripheral mode or host mode, and calls either usb_device_task() or usb_host_task() according to the ID pin (that determines the initial role configuration)
• The otg_user_task() handles both roles : connections and deconnections, high-level USB transferts and application level commands

Refer to the corresponding Application Note (OTG Add-on to USB Library) for a complete information guide about OTG and for more information about this package.

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