I'm currently designing a board arduino-compatible which embed an ATSAM3X8E like arduino-Due, but the problem is it is said on arduino website :
The SAM3X has 512 KB (2 blocks of 256 KB) of flash memory for storing code. The bootloader is preburned in factory from Atmel and is stored in a dedicated ROM memory.
I can't obtain ATSAM bootloader, but it seems the programming port is only necessary when you want to program ( which permit maybe the compatibility but not sure)
do you have an advise to make a board arduino compatible with ATSAM?
But I'm sure the ATSAM is working ( because I can program it with USB port)
And I have tried the UART communication ( With an oscilloscope) and I have seen that ATmega16u2 send data but ATSAM do not respond.
And after sending caracters throught UART communication from ATSAM to ATmega16u2, I have verify the TX pin of ATSAM so why the bootloader do not respond to the programmer?
So at least the SAM-BA is always part of every SAM3X8E device.
But 'helpers' like '1200 baud' hack for erase trigger is depending on your integration of arduino standards + external components like usb rs232 bridge etc.