SAM D21 Bootloader Cannot Upload

Hi there,

I am now trying to move to a standalone M0+ project and choose ATSAMD21E as the MCU. I have consulted with some online sources and decided to go with uploading with NATIVE USB port function. Currently, using ATMEL-ICE and arduino IDE make burning the bootloader possible, and the device manager does show "Arduino Zero bootloader(COMx1)."

However, when I upload the simplest blink example, I only 1 out of 20 times would I get a successful result, in the mean time I notice that the device manager would now turn to "Arduino Zero(COMx2)", a new port instead of the original one. Other 19 times or so would only have some "readValue" and "writeValue" message. At this moment it seems like the MCU was resetted, but sometimes the it would just go off, meaning that the device manager showed nothing. I could double-tap reset to enter bootloader again, letting the device manager show "Arduino Zero bootloader(COMx1)", but the rest of the process just keeps on looping without any luck.

I know there are a couple of things that are vague in this statement, but I really need help clarifying things here. Please let me know if you think there is anything I can try.

Thanks in advance!