I'm new to the forum, so forgive my ignorance, but I've had a problem and see if you can lend me a hand.
I created my own PCB with an atmel atsamd21g18aut, which is the same micro that is used in the Arduino Zero and in the M0 if I remember correctly.
Previously develop a PCB that used the same micro Due, and the advantage is that it brings factory bootloader and is practically soldering and programming, but in the case of Zero does not occur.
I have tried to program the micro through ISP which with an AVR micro like Arduino Uno can not.
And now is where your technological support comes in: - Is it possible to program the atsamd21g18aut by programming the arduino due as ISP? - Alternatively could you use the Atmel EDGB that uses the Due to schedule the atsamd21g18aut? - Is it possible to program it with samba using a USB-UART Bridge with an FTDI?
Right now the other option that I value is to use a socket of 48 pins and a j link and to program the bootloader with Atmel Studio.
As a conclusion, how can you load the bootloader to use native USB to an ATSAMD21G18AUT.