Memos From the Cube

Wowza. The 091223 LUFA release has had around 1100 downloads, nearly causing my server to go into conniptions. That’s easily more than double the number of releases of previous releases, and I’m pleased as punch with the increased uptake. I’m dying however to get a new release out with the major fixes to the AVRISP-MKII project code and other demos, but I want to complete TPI protocol support in the AVRISP-MKII project first. Thankfully it looks like I’ll have that working very soon, so we can all look forward to the next official release. I’m planning to have it enter a two week beta testing cycle (with the increased user-base, it is now more important to ensure each release is as free of defects as possible) beginning late this week.

I thought I’d fill up this entry with a short guide to loading my XPLAIN Bridge firmware into the XPLAIN board, after some coaxing. Without further ado, here it is!

Loading the XPLAIN Bridge code into the XPLAIN board

Step 1: Get the Source

Before you begin, you will need a fresh copy of the latest XPLAINBridge code. This is part of my LUFA project, however you will need the most recent in-development code instead of the latest LUFA release. Start by downloading a zipped package of all the latest LUFA code, straight from my online source repositories.

Extract out the entire package somewhere on your hard drive – a path without spaces is best (such as C:\AVR\LUFA_SRC\).

Step 2: Get the AVR-GCC Compiler and Tools

Most people should already have the required tools installed for AVR development, but I’ll put it here for completeness. On Windows, look no further than the WinAVR package – just download, install and you’re done. On Linux, grab the “avrgcc” package from your repositories. This will install the required compiler which can compile your source code into machine code that can be loaded into the AVR microcontrollers on the XPLAIN.

The other tool you’ll need is the Atmel FLIP software, which will act as our programming frontend for the USB AVR later on. Download and install it – if you are on an x64 based system, you’ll need these signed drivers instead.

Step 3: Build the Source

LUFA is a big project. No seriously, it’s HUGE and I’ve spent a lot of time on it. While it can make the USB AVR on the XPLAIN board to wondrous things with a minimum amount of pain, we’re only interested in one small project I’ve made with it. For that reason, you’ll need to navigate to the {LUFA Root Directory}/Projects/XPLAINBridge/ folder before you compile, lest you sit around for 10 minutes watching around 100,000 lines of source code be compiled.

Once in the XPLAINBridge project, you need to open up your terminal (that’s Command Prompt in Windows-land) and type make all. This will compile the XPLAINBridge code into the machine code needed for the AVR processor to execute.

When run, you’ll see a lot of similarly named files with different extensions be created. Most of these are related to the compiling itself, and we are only interested in the XPLAINBridge.hex file that is created – that’s the file which contains the compiled machine code for our programmer software to use.

Step 4: GET TO THE BOOTLOAAWDERRR!! (this is funny if you read it in an Arnold Schwarzenegger voice)

Unless you’re unlucky enough to have a first revision XPLAIN board (which 99.99% of you will not) your XPLAIN’s USB AVR comes preloaded with a special AVR program in it called a bootloader. This special program lives in the upper sections of the chip’s non-volatile FLASH memory, and allows you to reprogram the remainder of the memory with a regular AVR application through a non-standard interface (in this case directly from the USB port) without external hardware.

To get to the bootloader, you need to jumper the TCK pin to GND on the USB AVR JTAG header, that is, pins one and two shown here:

Jumper the circled pins to enter the bootloader.

When jumpered, plugging in the XPLAIN to a PC via the USB port will cause it to start it’s DFU class bootloader. You should get a driver popup under Windows – point it to {FLIP Install Directory}/usb for x86 systems, or to the drivers in the signed driver package you downloaded earlier for x64 systems.

Step 4: Program the USB AVR

After you have started FLIP, you should see a screen similar to the one below (click to enlarge).

The FLIP Interface.

First click the Select Target button (#1). From the dropdown, choose the AT90USB1287 entry (this is the USB AVR mounted on the XPLAIN board) and click OK to dismiss the window. Next, open the device via the Select Communication Medium button (#2) and choosing USB – click OK when the dialog opens up to establish a connection with your XPLAIN’s USB AVR.

Now you need to load the XPLAINBridge firmware into FLIP. To do this, click the Load HEX File button (#3) and select the XPLAINBridge.hex file you compiled earlier in step 3. Program it into the USB AVR by hitting the Run button (#4). Remove the jumper you placed earlier to access the DFU bootloader, then start the new firmware via the Start Application button (5). Don’t worry if you forget to remove the jumper before this step – just remove it and power cycle the board to exit the bootloader.

Step 5: Load the Bridge Drivers

By now, you should see a new driver window pop up, asking for the LUFA XPLAIN Bridge drivers. You’ve now successfully programmed in the bridge firmware! In the mode you are currently seeing, the firmware is acting as a USB-to-Serial bridge for the XMEGA AVR on the XPLAIN board. Before it will work correctly however, we need to supply the right drivers. In actual fact, Windows already contains the appropriate drivers, but you’ll need to supply the XPLAIN Bridge.inf file in the {LUFA Root Directory}/Projects/XPLAINBridge/ folder for it to use them. This will probably pop up an unsigned driver warning on your system — this is Microsoft’s fault (and not mine!) for not signing their own driver.

When loaded, you’ll be able to communicate with your XMEGA chip by the new virtual COM port the driver will create on your system.

Step 6: Load the PDI Programmer Drivers

The XPLAINBridge firmware contains a second mode – it can act as a clone of an Atmel AVRISP-MKII so that you can reprogram the XMEGA from within AVRStudio. To access this mode, you’ll need to jumper the TDI and GND pins of the USB AVR JTAG connector (pins 9 and 10) together and power-cycle the board, much like you did to enter the DFU bootloader:

Jumper the circled pins to switch to the programmer mode.

This should cause Windows to ask for a second set of drivers, for the new AVRISP-MKII Clone Programmer device. Point it to your {Atmel Program Files Folder}/AVR Tools/usb/ folder (for x86 systems) or {Atmel Program Files Folder}/AVR Tools/usb64/ folder (for x64 systems) and let it install Atmel’s drivers. You’ve now got yourself a programmer! To exit programming mode and return to the USB-to-Serial bridge mode, just remove the jumper you placed on the JTAG port and power cycle the board.

Step 7: Program the XMEGA AVR

When in programmer mode, you can reprogram the XPLAIN’s onboard ATXMEGA128A1 microcontroller via the PDI protocol, using any supported host software you like, such as AVRDude (note: PDI programming is broken in the latest release and requires manual patching) or Atmel’s own AVRStudio. For AVRStudio, you can follow the procedure in the AVR Tools help file, included with the application – just connect to the AVRISP MKII programmer, select the ATXMEGA128A1 target and use it like you would a regular AVRISP-MKII device.