I recently bought 8 ATSAM3X8E IC's to play with. Before going through the process of etching and such I decided to solder the IC on a protoboard and hook it up to a breadboard for testing (before designing the final board).
After hooking it up on the breadboard and plugging it in the USB port, nothing happens. No "pling plong, Windows" no nothing. It gets power and all, and the VDDCore is giving 1.8V as expected. But It's like I just connected some kind of charger to the PC, it gets power but no data exchange. D- and D+ on the USB are pulled low, which according to the datasheet means that the USB is disconnected (if I interpreted it right). I found a page in the datasheet that describes how the bootloader on the chip works, quote:
So if there is something wrong with the crystal then the bootloader will switch to the internal 12Mhz oscillator (which isn't as precise as the external) so the USB will be disconnected and the UART enabled instead. Which I believe means that the chip will only be programmed with UART.The SAM-BA Boot program seeks to detect a source clock either from the embedded main oscillator with external crystal (main oscillator enabled) or from a 12 MHz signal applied to the XIN
pin (Main oscillator in bypass mode).
If a clock is found from the two possible sources above, the boot program checks to verify that
the frequency is 12 MHz (taking into account the frequency range of the 32 kHz RC oscillator). If
the frequency is 12 MHz, USB activation is allowed, else (no clock or frequency other than
12MHz), the internal 12 MHz RC oscillator is used as main clock and USB clock is not allowed
due to frequency drift of the 12 MHz RC oscillator.
I've tried several 12MHz crystals, all with the same results. Maybe it's something else, maybe something I missed.
I've attached a schematic for how I hooked things up. Am I missing something important??? (Don't mind the lack of decoupling caps, I've included them on the breadboard).
Just for the record I've tried the same setup with two different ATSAM3X8E IC's.
Appreciate all the help I get!