CW305 and ATSAM3U

Hi all,

I just want to ask the role ATSAM3U plays; indeed, it is used for the USB interface; however, with a suitable bit file on the FPGA, we could demand FPGA to perform hardware crypto primitives via the UART communication between the CW-lite and FPGA, right? Then, is it necessary for an USB protocol for our capture and analysis?
I just studied the doc of CW305 hardware and the tutorial CW305_ECC, it’s a bit hard for me to figure out why do we need ATSAM3U here unless we want to do some firmware update.


Yes, it would be possible to talk to the FPGA target over UART. But the register interface that the SAM3U provides is much nicer to use for pure hardware targets, IMO.

The SAM3U does more than provide the register interface; if you look at the CW305 schematic, you’ll see that the SAM3U also controls the on-board programmable PLL and the XMEGA which in turn controls the programmable power supply and 7-segment displays. (And of course the ability to program bitfiles without an external adapter is very nice too.)

These extra features may not be strictly necessary for side-channel analysis, but they do make a lot of things easier. If all you need is a small FPGA target that you can only talk to over UART, then our S6LX9 target will do.


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Hey Jean,

If I want to use the CW305 on-board FPGA to simulate an IC, should I build an USB interface between it and SAM3U? Or I just choose the IC bitfile and follow the manner we did in CW305_ECC?


I don’t understand the question – the CW305 ECC demo does use the SAM3U “USB” interface.
As I used to say when Perl was in vogue, “TIMTOWTDI”. Do whatever makes sense for your project. Our AES and ECC demos use the SAM3U interface. Our ARM “DesignStart” demo uses the serial interface: