This is an old revision of the document!
The software running in the USB2AX can be updated or changed, to fix bugs, to add new functionalities or to tailor its behavior to your application.
The latest official firmware binary can be found on the firmware page.
You have a new firmware and you want to put it in the USB2AX, Great! There are three ways to do it:
For most people, the Regular procedure will work nicely. It is supported by the firmwares made by Xevelabs.
This update method is supported both for Windows and Linux.
Tested on Win7 64bits.
Tested on Ubuntu 10.10 32bits.
1) Install dfu-programmer >=0.5.4
WARNING Debian Squeeze only has 0.5.1, so on this distribution you might have to build it from sources.
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: usb2ax_run_bootload.py
Edit it to change the tty port accordingly. It requires Python 2.7 and PySerial.
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
The Recovery mode is mostly there as a fail-safe: if something goes horribly wrong with the Regular 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 a two step process: running the bootloader, then uploading the firmware into the flash memory. Only the first part is detailed here since the second is the same as in the Regular way.
Please be aware that attempting these is done at your own risks!
To run the bootloader manually, you need to get access to the pads on the bottom of the board. Either remove completely the clear protective plastic or just cut out the part that exposes the 3 pads on the side of the board.
The 3 pads are labeled GND, HWB and RST. The goal is to be able to connect GND with the two others, then release RST, then release HWB more than half a second later. There are various ways to do it, here are some suggestions.
Solder a button between GND and HWB, and the other one between GND and RST. Press the two buttons, then release the one that goes to RST, and a second later the other one.
Solder a small capacitor (in the uF range) between GND and HWB, and a button between GND and RST. When you press the button for a second or two, this will discharge the capacitor, and when you release the button, it will keep the voltage on HWB low enough for long enough for the bootloader to run.
Take a pair of metallic fine tweezers or a cable with stripped ends, touch one end on the GND pad and the other one successively on HWB (leave it for a second) and RST (just touch it). You will get better results if you switch from one to the other very quickly. If you are lucky, the stray capacitance of the HWB trace maintains it low enough for long enough for the bootloader to run.
The ICSP method allows you to change the bootloader or do away with it to use the remaining 4k of FLASH, but requires an ICSP programmer and some soldering.
To connect the ICSP to the board, the necessary pads are broken out on the bottom. You will need to remove the clear protection around the board, then connect:
ICSP pin number ↔ pin functionality ↔ place to get it on the USB2AX
The rest is up to you, from there it's like programming any other AVR MCU. Have fun!
The sources of the firmware are available in the Git Repository of the project.
Read the README file to get an idea of what is going on, read the code, and start hacking away!