Programming a ATSAMD21E18A without bootloader

[heliosoph]

At the moment I am designing a custom board with the ATSAMD21E18A. I want to program the controller directly via SWD without using a bootloader and USB. This could save me a USB connector on my board. For initial tests the controller sits on a breadboard. My programmer is the Atmel ICE. Connection via openocd is fine.

In the Arduino IDE I selected
SAMD DevBoards, Board "SAMD21E DevBoard", Microcontroller "SAMD21E18A", Clock Source "Internal Oscillator", USB Config "USB disabled", Serial Config "1xUART, 1xWIRE, 1xSPI", Bootloader "No Bootloader", Timer PWM Frequency "732.4Hz (16Bit)", Floating Point "Print & String use auto-promoted doubles only" Build Options "config.h disabled"

I was able to upload the blink example. It worked but I got some error messages that I unfortunately didn't copy. The blink example is running but the chip is bricked. No SWD connection is possible.

My questions are: Did you ever test uploading a sketch from the IDE without bootloader? Do you see any errors in what I did? Do you have any recommendations?

Thanks in advance

heliosoph