ATMEL AVR1922 User Manual

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AVR1922: Xplain Board Controller Firmware

Features

• USB interface

- Mass-storage to on-board DataFlash® memory

• Atmel® AVR® XMEGATM reset control

1 Introduction

The Xplain board controller, an AT90USB1287, is in charge of some of the low­level tasks on boards in the Xplain series. The board controller improves usability
of the main microcontroller, and adds features the main controller lacks, like USB.

Some of the tasks the board controller can handle are moving data to and from the
board over the USB interface, for example mass-storage or USB-to-serial.

Note that not all Xplain boards carry multiple microcontrollers; in these cases the
main microcontroller will provide the board controller features when applicable.

Figure 1-1. Board controller on the Xplain board marked in a red circle

8-bit
Microcontrollers

Application Note

Rev. 8302A-AVR-04/10

2 Xplain Board Controller Hardware Features

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This chapter will walk through the features available when having a separate board
controller.

2.1 USB Interface

All Xplain boards features an USB connector. This connector has a dual purpose;
power and USB interfaces. When the USB connector is wired to the board controller,
it can be used for various tasks depending on the firmware.

2.1.1 USB-to-serial Interface

n

The mai
port can then be shared as a CDC/ACM USB class (USB-to-serial) on the USB
interface. Having a USB-to-serial interface can be useful for debugging the main
application running on the board, or for transferring data back and forth to an external
host.

2.1.2 USB Mass-storage Interface

Whe
for the board controller as mass-storage devices on the USB interface. This will
present the on-board flash memory as a block device on the host side, and users are
free to use them as they like. Typically storing data files, images, etc. there, for use
with the main microcontroller.

microcontroller will have one UART wired to the board controller. This serial

n

connected to a PC the Xplain board can share any external memories available

2.2 AVR XMEGA Reset Line Control

The board controller has wired an I/O line to the AVR XMEGA reset line. This line can
be used to control the reset state of the main microcontroller.

2.3 AVR XMEGA Program and Debug Interface

To program the main microcontroller, the board controller is wired to the program and
debug interface (PDI) on the AVR XMEGA device. This interface can be used to
program new firmware into the main microcontroller from the board controller.

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3 Xplain Board Controller Firmware

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3.1 Features

The board controller firmware currently supports the following features:

• DataFlash initialization read and write.

• AVR XMEGA reset control.

• USB mass-storage interface.

• USB mode switching.

The firmware will on power up hold the AVR XMEGA device in reset while it tries to
probe the on-board DataFlash memory. When the firmware has identified the
DataFlash device it will read the level of an I/O line to select USB mode.

A low level on the I/O line will make the AT90USB1287 chip enter mass-storage
mode and share the DataFlash on the USB interface, thus keeping the AVR XMEGA
device in reset.

If the I/O is high, the AT90USB1287 chip will release the AVR XMEGA device and
enter a slave like presence, not interfering with the AVR XMEGA. The AVR XMEGA
is now free to access the DataFlash on the board without interference.

AVR1922

Table 3-1. Board Controller USB mode switching functionality overview

I/O line level AVR XMEGA reset USB mass-storage

Left floating / high level Released after init Disabled
Pulled low / low level Held in reset after init Enabled

For specific mode switching behavior on the Xplain board, see chapter 3.1.1 USB
Mode Switchi

For more info
storage Interf

ng on the Xplain Board on page 4.

rmation about the mass-storage interface see chapter 2.1.2 USB Mass-

ace on page 2.

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3.1.1 USB Mode Switching on the Xplain Board

To sele
either pull the TDI pin on the JTAG USB header to ground or leave it floating. This is
done by placing a jumper between TDI and GND pin, see the figure below.

Figure 3-1. USB mode switch pins located on the Xplain board

ct between the two different USB modes on the Xplain board, the user has to

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3.2 Compiling the Board Controller Firmware

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The following step by step guide will compile the board controller firmware for the
Xplain board.

1. Download and uncompress the compressed file archive from

www.atmel.com/products/AVR -> Application Notes -> AVR1922 Xplain
Board Controller Firmware containing the Xplain board controller source

code.

2. Open up your favorite command line console and change into the directory
extracted from the compressed file archive.

3. Enter the apps/xplain-bc directory.

4. Compile the application by telling the build system what kind of configuration
you would like to use. This is done by setting the CONFIG symbol. For
additional help, type make help on the command line. See the example below
for how to compile for the Xplain board:

make CONFIG=xplain-bc

5. The application’s output binaries will be in the top level
build/xplain-bc/xplain-bc/GNU directory. The xplain-bc.elf and xplain-bc.hex
files are probably most interesting. If the user does not use the GNU
toolchain, the GCC part of the path must be changed appropriately. Also, the
board name must be changed if another configuration has been used.

AVR1922

6. Use your favorite programming software and tool to program the ELF or HEX
file into the AT90USB1287 chip on the Xplain board. See chapter 4.1
Reprogramming the Xplain AT90USB1287 and ATxmega128A1 Firmware for
further details.

4 Suggested Reading

4.1 Reprogramming the Xplain AT90USB1287 and ATxmega128A1 Firmware

For details about how to program either device on the Xplain board see the
application note AVR1921: Reprogramming the Xplain AT90USB1287 and
ATxmega128A1 Firmware. This describes how to program the devices using either a
programming tool, like AVRONE!, JTAGICE mkII or AVR Dragon, or programming
software, like FLIP.

The application note is available from the website at
www.atmel.com/dyn/products/tools_card_v2.asp?tool_id=4506.

4.2 Display Xplained Firmware – Getting Started

It is recommended to look into the AVR1913: Display Xplained Firmware – Getting
Started application note, as this describes how the build system works and how to

start using the software framework.
The application note is available from the website at

www.atmel.com/dyn/products/tools_card_v2.asp?tool_id=4506.

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