Hi All,
I've created a PCBA that is essentially a combination of 3 reference designs: an Arduino Due, an Adafruit RA8875 controller board, and a little flash storage circuitry. The Due circuitry contains everything that is on your typical Arduino Due.
I was able to successfully load the bootloader onto the 16u2 uC, and it's correctly being read by my PC and Arduino IDE as a 'Arduino Due (Programming Port)'. However, when I try uploading the blink sketch to the board, I just get the RX LED of the 16u2 flickering for half a second and nothing on the TX LED before getting the following error:
No device found on cu.usbmodem14E11
An error occurred while uploading the sketch
I want to see if there's any help that anyone could provide on debugging this (without a debugger - currently in the process of buying one, if necessary). The RX line of the Sam3x8e is receiving data from the 16u2 (checked with oscilloscope for activity), but I'm not sure where else to go from here. If the 16u2 is being read correctly by the IDE, is it certain that the 16u2 is sending information correctly and therefore is it definitely a problem on the Sam3x8e side? I'm going pin by pin to make sure everything was soldered correctly, but from what I can see everything looks good.
Sidenote: the only thing that was not soldered by the board house were the crystals for both the Sam3x8e and the 16u2, is it possible that I botched this? 
**Attached are two screenshots of a 16u2's TX pin on an Arduino Due vs that of my board. My board seems to have more of a slow fall to it, could it be that its too slow for the Sam3x8e to read? What could be causing this?
Thanks in advance for the help!
Pat
