Xevelabs Product Documentation

The software running in the USB2AX can be updated or changed, to add new functionalities or to tailor its behavior to your application.

You have a new firmware and you want to put it in the USB2AX, Great! There are three ways to do it:

• Automatic - for normal firmware update, with minimal user action.
• Recovery - for when something went wrong with the Automatic mode, or for custom firmwares. Requires actions on the board.
• ICSP - for geeks.

For most people, the Automatic procedure will work nicely. It is supported by the firmwares made by Xevelabs, and relied upon by the automatic firmware update tool.

This update method is supported both for Windows and Linux.

Windows version
Tested on Win7 64bits.
Prerequisites:

• Installing Atmel FLIP
• Getting the USB2AX_Update application
• …

Linux Version
Tested on Ubuntu 10.10 32bits.

1) Install dfu-programmer >=0.5.4 (as of today, the version in the package repository of Debian is 0.5.1, so build it from sources):

apt-get install libusb-dev
#download and uncompress dfu-programmer
cd dfu-programmer-<version>
./configure
make

The binary is in ./src

Maybe add the user to the uucp group so you don't have to run dfu-programmer as root… but it did not work for me.

2) Run the bootloader using the python script.

3) Run the programmer :

./dfu-programmer atmega32u2 erase
./dfu-programmer atmega32u2 flash USB2AX.hex
#/!\: the .hex needs to have UNIX-style end of lines (\n, LF), and will not work with DOS end of lines (\r\n CRLF).
./dfu-programmer atmega32u2 start

• Running the bootloader on the USB2AX is as simple as sending on its serial port the following ascii string: 0xff 0xff 0xfd 0x02 0x08 0xf8

Here is an example in Python, the latest revsion of which you can be found in the git repository (usb2ax_run_bootload.py):

import serial
bootload_cmd = '\xff\xff\xfd\x02\x08\xf8'
ser = serial.Serial("COM7")
ser.write(bootload_cmd)
ser.close()

• For commands aimed at the USB2AX, time between two bytes must not exceed 2ms. However, for commands sent to the servos, the maximum byte to byte time acceptable is of 100ms (see http://support.robotis.com/en/product/dynamixel/dxl_communication.htm ).

• When the command is received, the USB2AX removes itself from the USB bus immediately and waits two seconds before re-enumerating.

• The bootlaoder is the factory-programed one made by Atmel. On windows, the USB2AX running the bootloader will appear as “ATmega32u2” in the “Atmel Devices” section of the Device Manager.

The Recovery mode is mostly there as a failsafe: if something goes horribly wrong with the Automatic way or if you want to use a third party firmware, you can always get back to a working state without an additional programmer.

Doing that is normally a two step process : running the bootloader, then uploading the firmware into the flash memory.

The ICSP method allows you to change the bootloader or do away with it, but requires an ISP programmer and some soldering.