i build a custom board with an ATSAMD21E17D, similar to adafruit's Trinket M0, but with more used pins and different pinmux. I sucessfully burned the adafruit UF2 bootloader for that board using Atmel Studio and an ICE-3 programmer.
After powerup the pin13 LED is "breathing", I see the COM Port and a flash drive is mounted. When i try to flash the "Blink" example the LED shortly flashes and then arduino IDE throws an "No Device Found at COM4" error. Setup of Arduino IDE is correct, an original trinket M0 is flashable.
: I looked up the chip ID again and found out that the "D" in the end stands for
D = Silicon Revision G with RWW Support in 128KB memory options
maybe the Bootloader cannot handle this??? RWW stands for "Read while write" and is related to bootloader and how it can write to the flash.
Any ideas? Thanks in advance