As promised. After spending a day trying to download code onto the board, I’ve finally figure it out. Since it was such a pain, I thought that I should note things down here to help others.
While it was fraught with pain, it was a worthwhile journey. I learned a lot about the board and AVR32 platform. The biggest lesson that I took away was how much effort ATMEL had spent into building its libraries for its platforms. There is no wonder why Arduinos were birthed on this platform.
I will learn from this and hope to build a better platform for my processor, which is currently only usable by elite hackers.
The first thing to note is that there are 2 AVR32 processors on the board. The one that is directly programmable via the USB DFU interface is the smaller one, hardly noticeable, sitting right next to the ethernet socket.
It is a AT32UC3B1256 processor. While it is entirely programmable, it is not really connected to much. The one that is connected to all the bells and whistles is the AT32UCA0512, which is the big one in the centre of the board. However, it’s not directly programmable. I’ll get to that in a bit.
It took me a while to figure this one out as I was successfully programming the smaller one but nothing seemed to be happening. All the while, I thought that I was programming the bigger one. Sigh.
Faulty AT32UC3B1256 Firmware
The smaller AVR shipped with a faulty firmware, which did not allow it to run in USB-RS232 bridge mode. I had to download the fixed firmware from ATMEL and reprogram the chip. Thankfully, I could program this smaller one easily and it worked.
This smaller one could also function in as a limited JTAG. Unfortunately, the resistors that connect the smaller AVR to the JTAG pins of the bigger AVR are not soldered on the board. They’re right at the back of the board and it’s just not there.
I discovered this when snooping around the official schematics for the board, without which I would not even know of the existence of this JTAG function. While snooping around the schematics, I discovered how to program the bigger AVR.
Programming the AT32UC3A0512
There are a number of ways to program the bigger AVR – using the JTAG port, which necessitates buying an expensive JTAG cable; or using the USB DFU boot-loader interface, which is not present. However, I could never get the bigger AVR to enter ISP mode regardless of how much button pressing voodoo I did.
There is a BOOTSEL button on the board, which is unfortunately connected to the smaller AVR. Therefore, it would only put the smaller AVR into ISP mode and not the bigger AVR. To get the big AVR into ISP mode, I had to use a resistor to short out pins J16.1 and J16.9 together.
Read that. I had to short out the pins on the board directly. It’s an ugly hack. Once I did that, the larger AVR would enter into ISP mode and I was able to program it to my hearts desire, accessing all the bells and whistles on the board.